diff --git a/src/constraint/alldifferent.rs b/src/constraint/alldifferent.rs
index 744b239..c69a10c 100644
--- a/src/constraint/alldifferent.rs
+++ b/src/constraint/alldifferent.rs
@@ -3,7 +3,7 @@
 use std::collections::HashMap;
 use std::rc::Rc;
 
-use crate::{Constraint,PsResult,PuzzleSearch,Val,VarToken};
+use crate::{Constraint, PsResult, PuzzleSearch, Val, VarToken};
 
 pub struct AllDifferent {
     vars: Vec<VarToken>,
@@ -22,7 +22,9 @@ impl AllDifferent {
     /// puzzle_solver::constraint::AllDifferent::new(&vars);
     /// ```
     pub fn new<'a, I>(vars: I) -> Self
-            where I: IntoIterator<Item=&'a VarToken> {
+    where
+        I: IntoIterator<Item = &'a VarToken>,
+    {
         AllDifferent {
             vars: vars.into_iter().cloned().collect(),
         }
@@ -30,12 +32,11 @@ impl AllDifferent {
 }
 
 impl Constraint for AllDifferent {
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a> {
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a> {
         Box::new(self.vars.iter())
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val)
-            -> PsResult<()> {
+    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
         for &var2 in self.vars.iter().filter(|&v| *v != var) {
             r#try!(search.remove_candidate(var2, val));
         }
@@ -75,13 +76,12 @@ impl Constraint for AllDifferent {
         Ok(())
     }
 
-    fn substitute(&self, from: VarToken, to: VarToken)
-            -> PsResult<Rc<dyn Constraint>> {
+    fn substitute(&self, from: VarToken, to: VarToken) -> PsResult<Rc<dyn Constraint>> {
         if let Some(idx) = self.vars.iter().position(|&var| var == from) {
             if !self.vars.contains(&to) {
                 let mut new_vars = self.vars.clone();
                 new_vars[idx] = to;
-                return Ok(Rc::new(AllDifferent{ vars: new_vars }));
+                return Ok(Rc::new(AllDifferent { vars: new_vars }));
             }
         }
 
@@ -91,16 +91,16 @@ impl Constraint for AllDifferent {
 
 #[cfg(test)]
 mod tests {
-    use crate::{Puzzle,Val};
+    use crate::{Puzzle, Val};
 
     #[test]
     fn test_contradiction() {
         let mut puzzle = Puzzle::new();
         let v0 = puzzle.new_var_with_candidates(&[1]);
         let v1 = puzzle.new_var_with_candidates(&[1]);
-        let v2 = puzzle.new_var_with_candidates(&[1,2,3]);
+        let v2 = puzzle.new_var_with_candidates(&[1, 2, 3]);
 
-        puzzle.all_different(&[v0,v1,v2]);
+        puzzle.all_different(&[v0, v1, v2]);
 
         let solution = puzzle.solve_any();
         assert!(solution.is_none());
@@ -110,25 +110,25 @@ mod tests {
     fn test_elimination() {
         let mut puzzle = Puzzle::new();
         let v0 = puzzle.new_var_with_candidates(&[1]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2,3]);
-        let v2 = puzzle.new_var_with_candidates(&[1,2,3]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2, 3]);
+        let v2 = puzzle.new_var_with_candidates(&[1, 2, 3]);
 
-        puzzle.all_different(&[v0,v1,v2]);
+        puzzle.all_different(&[v0, v1, v2]);
 
         let search = puzzle.step().expect("contradiction");
         assert_eq!(search[v0], 1);
-        assert_eq!(search.get_unassigned(v1).collect::<Vec<Val>>(), &[2,3]);
-        assert_eq!(search.get_unassigned(v2).collect::<Vec<Val>>(), &[2,3]);
+        assert_eq!(search.get_unassigned(v1).collect::<Vec<Val>>(), &[2, 3]);
+        assert_eq!(search.get_unassigned(v2).collect::<Vec<Val>>(), &[2, 3]);
     }
 
     #[test]
     fn test_contradiction_by_length() {
         let mut puzzle = Puzzle::new();
-        let v0 = puzzle.new_var_with_candidates(&[1,2]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2]);
-        let v2 = puzzle.new_var_with_candidates(&[1,2]);
+        let v0 = puzzle.new_var_with_candidates(&[1, 2]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2]);
+        let v2 = puzzle.new_var_with_candidates(&[1, 2]);
 
-        puzzle.all_different(&[v0,v1,v2]);
+        puzzle.all_different(&[v0, v1, v2]);
 
         let search = puzzle.step();
         assert!(search.is_none());
@@ -137,15 +137,15 @@ mod tests {
     #[test]
     fn test_constrain_by_value() {
         let mut puzzle = Puzzle::new();
-        let v0 = puzzle.new_var_with_candidates(&[1,2]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2]);
-        let v2 = puzzle.new_var_with_candidates(&[1,2,3]);
+        let v0 = puzzle.new_var_with_candidates(&[1, 2]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2]);
+        let v2 = puzzle.new_var_with_candidates(&[1, 2, 3]);
 
-        puzzle.all_different(&[v0,v1,v2]);
+        puzzle.all_different(&[v0, v1, v2]);
 
         let search = puzzle.step().expect("contradiction");
-        assert_eq!(search.get_unassigned(v0).collect::<Vec<Val>>(), &[1,2]);
-        assert_eq!(search.get_unassigned(v1).collect::<Vec<Val>>(), &[1,2]);
+        assert_eq!(search.get_unassigned(v0).collect::<Vec<Val>>(), &[1, 2]);
+        assert_eq!(search.get_unassigned(v1).collect::<Vec<Val>>(), &[1, 2]);
         assert_eq!(search[v2], 3);
     }
 }
diff --git a/src/constraint/equality.rs b/src/constraint/equality.rs
index 94e512d..6b4e409 100644
--- a/src/constraint/equality.rs
+++ b/src/constraint/equality.rs
@@ -1,10 +1,10 @@
 //! Equality implementation.
 
-use std::rc::Rc;
 use num_rational::Ratio;
 use num_traits::Zero;
+use std::rc::Rc;
 
-use crate::{Constraint,LinExpr,PsResult,PuzzleSearch,Val,VarToken};
+use crate::{Constraint, LinExpr, PsResult, PuzzleSearch, Val, VarToken};
 
 pub struct Equality {
     // The equation: 0 = constant + coef1 * var1 + coef2 * var2 + ...
@@ -25,19 +25,16 @@ impl Equality {
     ///         vars[0][0] + vars[0][1] + vars[0][2] - 15);
     /// ```
     pub fn new(eqn: LinExpr) -> Self {
-        Equality {
-            eqn: eqn,
-        }
+        Equality { eqn: eqn }
     }
 }
 
 impl Constraint for Equality {
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a> {
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a> {
         Box::new(self.eqn.coef.keys())
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, _: VarToken, _: Val)
-            -> PsResult<()> {
+    fn on_assigned(&self, search: &mut PuzzleSearch, _: VarToken, _: Val) -> PsResult<()> {
         let mut sum = self.eqn.constant;
         let mut unassigned_var = None;
 
@@ -108,16 +105,24 @@ impl Constraint for Equality {
             let (min_bnd, max_bnd);
 
             if coef > Ratio::zero() {
-                min_bnd = ((coef * Ratio::from_integer(max_val) - sum_max) / coef).ceil().to_integer();
-                max_bnd = ((coef * Ratio::from_integer(min_val) - sum_min) / coef).floor().to_integer();
+                min_bnd = ((coef * Ratio::from_integer(max_val) - sum_max) / coef)
+                    .ceil()
+                    .to_integer();
+                max_bnd = ((coef * Ratio::from_integer(min_val) - sum_min) / coef)
+                    .floor()
+                    .to_integer();
             } else {
-                min_bnd = ((coef * Ratio::from_integer(max_val) - sum_min) / coef).ceil().to_integer();
-                max_bnd = ((coef * Ratio::from_integer(min_val) - sum_max) / coef).floor().to_integer();
+                min_bnd = ((coef * Ratio::from_integer(max_val) - sum_min) / coef)
+                    .ceil()
+                    .to_integer();
+                max_bnd = ((coef * Ratio::from_integer(min_val) - sum_max) / coef)
+                    .floor()
+                    .to_integer();
             }
 
             if min_val < min_bnd || max_bnd < max_val {
-                let (new_min, new_max)
-                    = r#try!(search.bound_candidate_range(var, min_bnd, max_bnd));
+                let (new_min, new_max) =
+                    r#try!(search.bound_candidate_range(var, min_bnd, max_bnd));
 
                 if coef > Ratio::zero() {
                     sum_min = sum_min + coef * Ratio::from_integer(new_min - min_val);
@@ -134,26 +139,25 @@ impl Constraint for Equality {
         Ok(())
     }
 
-    fn substitute(&self, from: VarToken, to: VarToken)
-            -> PsResult<Rc<dyn Constraint>> {
+    fn substitute(&self, from: VarToken, to: VarToken) -> PsResult<Rc<dyn Constraint>> {
         let mut eqn = self.eqn.clone();
         if let Some(coef) = eqn.coef.remove(&from) {
             eqn = eqn + coef * to;
         }
 
-        Ok(Rc::new(Equality{ eqn: eqn }))
+        Ok(Rc::new(Equality { eqn: eqn }))
     }
 }
 
 #[cfg(test)]
 mod tests {
-    use crate::{Puzzle,Val};
+    use crate::{Puzzle, Val};
 
     #[test]
     fn test_contradiction() {
         let mut puzzle = Puzzle::new();
         let v0 = puzzle.new_var_with_candidates(&[3]);
-        let v1 = puzzle.new_var_with_candidates(&[0,1]);
+        let v1 = puzzle.new_var_with_candidates(&[0, 1]);
 
         puzzle.equals(v0 + 2 * v1, 4);
 
@@ -165,7 +169,7 @@ mod tests {
     fn test_assign() {
         let mut puzzle = Puzzle::new();
         let v0 = puzzle.new_var_with_candidates(&[1]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2,3]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2, 3]);
 
         puzzle.equals(v0 + v1, 4);
 
@@ -177,13 +181,13 @@ mod tests {
     #[test]
     fn test_reduce_range() {
         let mut puzzle = Puzzle::new();
-        let v0 = puzzle.new_var_with_candidates(&[1,2,3]);
-        let v1 = puzzle.new_var_with_candidates(&[3,4,5]);
+        let v0 = puzzle.new_var_with_candidates(&[1, 2, 3]);
+        let v1 = puzzle.new_var_with_candidates(&[3, 4, 5]);
 
         puzzle.equals(v0 + v1, 5);
 
         let search = puzzle.step().expect("contradiction");
-        assert_eq!(search.get_unassigned(v0).collect::<Vec<Val>>(), &[1,2]);
-        assert_eq!(search.get_unassigned(v1).collect::<Vec<Val>>(), &[3,4]);
+        assert_eq!(search.get_unassigned(v0).collect::<Vec<Val>>(), &[1, 2]);
+        assert_eq!(search.get_unassigned(v1).collect::<Vec<Val>>(), &[3, 4]);
     }
 }
diff --git a/src/constraint/mod.rs b/src/constraint/mod.rs
index a6eb40e..74481f0 100644
--- a/src/constraint/mod.rs
+++ b/src/constraint/mod.rs
@@ -7,16 +7,15 @@
 
 use std::rc::Rc;
 
-use crate::{PsResult,PuzzleSearch,Val,VarToken};
+use crate::{PsResult, PuzzleSearch, Val, VarToken};
 
 /// Constraint trait.
 pub trait Constraint {
     /// An iterator over the variables that are involved in the constraint.
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a>;
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a>;
 
     /// Applied after a variable has been assigned.
-    fn on_assigned(&self, _search: &mut PuzzleSearch, _var: VarToken, _val: Val)
-            -> PsResult<()> {
+    fn on_assigned(&self, _search: &mut PuzzleSearch, _var: VarToken, _val: Val) -> PsResult<()> {
         Ok(())
     }
 
@@ -29,8 +28,7 @@ pub trait Constraint {
     ///
     /// Returns a new constraint with all instances of "from" replaced
     /// with "to", or Err if a contradiction was found.
-    fn substitute(&self, from: VarToken, to: VarToken)
-            -> PsResult<Rc<dyn Constraint>>;
+    fn substitute(&self, from: VarToken, to: VarToken) -> PsResult<Rc<dyn Constraint>>;
 }
 
 pub use self::alldifferent::AllDifferent;
diff --git a/src/constraint/unify.rs b/src/constraint/unify.rs
index 4c5661f..c05e6f3 100644
--- a/src/constraint/unify.rs
+++ b/src/constraint/unify.rs
@@ -3,7 +3,7 @@
 use std::iter;
 use std::rc::Rc;
 
-use crate::{Constraint,PsResult,PuzzleSearch,VarToken};
+use crate::{Constraint, PsResult, PuzzleSearch, VarToken};
 
 pub struct Unify {
     var1: VarToken,
@@ -33,7 +33,7 @@ impl Unify {
 }
 
 impl Constraint for Unify {
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a> {
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a> {
         if self.var1 != self.var2 {
             Box::new(iter::once(&self.var1).chain(iter::once(&self.var2)))
         } else {
@@ -49,11 +49,13 @@ impl Constraint for Unify {
         }
     }
 
-    fn substitute(&self, from: VarToken, to: VarToken)
-            -> PsResult<Rc<dyn Constraint>> {
+    fn substitute(&self, from: VarToken, to: VarToken) -> PsResult<Rc<dyn Constraint>> {
         let var1 = if self.var1 == from { to } else { self.var1 };
         let var2 = if self.var2 == from { to } else { self.var2 };
-        Ok(Rc::new(Unify{ var1: var1, var2: var2 }))
+        Ok(Rc::new(Unify {
+            var1: var1,
+            var2: var2,
+        }))
     }
 }
 
@@ -64,8 +66,8 @@ mod tests {
     #[test]
     fn test_unify_alldifferent() {
         let mut puzzle = Puzzle::new();
-        let v0 = puzzle.new_var_with_candidates(&[1,2]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2]);
+        let v0 = puzzle.new_var_with_candidates(&[1, 2]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2]);
 
         puzzle.all_different(&[v0, v1]);
         puzzle.unify(v0, v1);
@@ -77,9 +79,9 @@ mod tests {
     #[test]
     fn test_unify_equality() {
         let mut puzzle = Puzzle::new();
-        let v0 = puzzle.new_var_with_candidates(&[1,2,3,4]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2,3,4]);
-        let v2 = puzzle.new_var_with_candidates(&[1,2,3,4]);
+        let v0 = puzzle.new_var_with_candidates(&[1, 2, 3, 4]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2, 3, 4]);
+        let v2 = puzzle.new_var_with_candidates(&[1, 2, 3, 4]);
 
         puzzle.equals(v0 + 2 * v1 + v2, 6);
         puzzle.unify(v0, v1);
@@ -94,8 +96,8 @@ mod tests {
     fn test_unify_unify() {
         let mut puzzle = Puzzle::new();
         let v0 = puzzle.new_var_with_candidates(&[1]);
-        let v1 = puzzle.new_var_with_candidates(&[1,2,3,4]);
-        let v2 = puzzle.new_var_with_candidates(&[1,2,3,4]);
+        let v1 = puzzle.new_var_with_candidates(&[1, 2, 3, 4]);
+        let v2 = puzzle.new_var_with_candidates(&[1, 2, 3, 4]);
 
         puzzle.unify(v0, v1);
         puzzle.unify(v1, v2);
diff --git a/src/lib.rs b/src/lib.rs
index 863e668..db24ce4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -5,16 +5,16 @@ extern crate bit_set;
 extern crate num_rational;
 extern crate num_traits;
 
+use num_rational::Rational32;
 use std::collections::HashMap;
 use std::ops;
-use num_rational::Rational32;
 
 pub use crate::constraint::Constraint;
 pub use crate::puzzle::Puzzle;
 pub use crate::puzzle::PuzzleSearch;
 
 /// A puzzle variable token.
-#[derive(Copy,Clone,Debug,Eq,Hash,PartialEq)]
+#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
 pub struct VarToken(usize);
 
 /// The type of a puzzle variable's value (i.e. the candidate type).
diff --git a/src/linexpr.rs b/src/linexpr.rs
index 4fcbd05..5334e9b 100644
--- a/src/linexpr.rs
+++ b/src/linexpr.rs
@@ -1,25 +1,29 @@
 //! Linear expressions.
 
-use std::collections::HashMap;
+use num_rational::{Ratio, Rational32};
+use num_traits::{One, Zero};
 use std::collections::hash_map::Entry;
+use std::collections::HashMap;
 use std::convert::From;
-use std::ops::{Add,Mul,Neg,Sub};
-use num_rational::{Ratio,Rational32};
-use num_traits::{One,Zero};
+use std::ops::{Add, Mul, Neg, Sub};
 
-use crate::{Coef,LinExpr,VarToken};
+use crate::{Coef, LinExpr, VarToken};
 
 macro_rules! impl_commutative_op {
     ($LHS:ident + $RHS:ident) => {
         impl Add<$RHS> for $LHS {
             type Output = LinExpr;
-            fn add(self, rhs: $RHS) -> Self::Output { rhs + self }
+            fn add(self, rhs: $RHS) -> Self::Output {
+                rhs + self
+            }
         }
     };
     ($LHS:ident * $RHS:ident) => {
         impl Mul<$RHS> for $LHS {
             type Output = LinExpr;
-            fn mul(self, rhs: $RHS) -> Self::Output { rhs * self }
+            fn mul(self, rhs: $RHS) -> Self::Output {
+                rhs * self
+            }
         }
     };
 }
@@ -28,9 +32,11 @@ macro_rules! impl_subtract_op {
     ($LHS:ident - $RHS:ident) => {
         impl Sub<$RHS> for $LHS {
             type Output = LinExpr;
-            fn sub(self, rhs: $RHS) -> Self::Output { self + (-rhs) }
+            fn sub(self, rhs: $RHS) -> Self::Output {
+                self + (-rhs)
+            }
         }
-    }
+    };
 }
 
 pub trait IntoCoef: Zero {
@@ -38,11 +44,15 @@ pub trait IntoCoef: Zero {
 }
 
 impl IntoCoef for i32 {
-    fn into_coef(self) -> Coef { Ratio::from_integer(self) }
+    fn into_coef(self) -> Coef {
+        Ratio::from_integer(self)
+    }
 }
 
 impl IntoCoef for Rational32 {
-    fn into_coef(self) -> Coef { self }
+    fn into_coef(self) -> Coef {
+        self
+    }
 }
 
 /*--------------------------------------------------------------*/
@@ -196,7 +206,7 @@ impl Add for LinExpr {
             match self.coef.entry(x2) {
                 Entry::Vacant(e) => {
                     e.insert(a2);
-                },
+                }
                 Entry::Occupied(mut e) => {
                     let new_coef = *e.get() + a2;
                     if new_coef.is_zero() {
@@ -204,7 +214,7 @@ impl Add for LinExpr {
                     } else {
                         *e.get_mut() = new_coef;
                     }
-                },
+                }
             }
         }
 
@@ -218,8 +228,8 @@ impl_subtract_op!(LinExpr - LinExpr);
 
 #[cfg(test)]
 mod tests {
-    use num_rational::Ratio;
     use crate::Puzzle;
+    use num_rational::Ratio;
 
     #[test]
     fn test_ops() {
diff --git a/src/puzzle.rs b/src/puzzle.rs
index e8f7a6b..996466d 100644
--- a/src/puzzle.rs
+++ b/src/puzzle.rs
@@ -1,5 +1,6 @@
 //! The puzzle's state and rules.
 
+use bit_set::BitSet;
 use std::cell::Cell;
 use std::collections::BTreeSet;
 use std::fmt;
@@ -7,21 +8,20 @@ use std::iter;
 use std::mem;
 use std::ops;
 use std::rc::Rc;
-use bit_set::BitSet;
 
-use crate::{Constraint,LinExpr,PsResult,Solution,Val,VarToken};
 use crate::constraint;
+use crate::{Constraint, LinExpr, PsResult, Solution, Val, VarToken};
 
 /// A collection of candidates.
-#[derive(Clone,Debug,Eq,PartialEq)]
+#[derive(Clone, Debug, Eq, PartialEq)]
 enum Candidates {
-    None,                       // A variable with no candidates.
-    Value(Val),                 // A variable set to its initial value.
-    Set(Rc<BTreeSet<Val>>),     // A variable with a list of candidates.
+    None,                   // A variable with no candidates.
+    Value(Val),             // A variable set to its initial value.
+    Set(Rc<BTreeSet<Val>>), // A variable with a list of candidates.
 }
 
 /// The state of a variable during the solution search.
-#[derive(Clone,Debug)]
+#[derive(Clone, Debug)]
 enum VarState {
     Assigned(Val),
     Unassigned(Candidates),
@@ -78,7 +78,7 @@ impl Candidates {
     }
 
     /// Get an iterator over all of the candidates of a variable.
-    fn iter<'a>(&'a self) -> Box<dyn Iterator<Item=Val> + 'a> {
+    fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = Val> + 'a> {
         match self {
             &Candidates::None => Box::new(iter::empty()),
             &Candidates::Value(val) => Box::new(iter::once(val)),
@@ -146,8 +146,7 @@ impl Puzzle {
     /// let mut send_more_money = puzzle_solver::Puzzle::new();
     /// send_more_money.new_vars_with_candidates_1d(8, &[0,1,2,3,4,5,6,7,8,9]);
     /// ```
-    pub fn new_vars_with_candidates_1d(&mut self, n: usize, candidates: &[Val])
-            -> Vec<VarToken> {
+    pub fn new_vars_with_candidates_1d(&mut self, n: usize, candidates: &[Val]) -> Vec<VarToken> {
         let mut vars = Vec::with_capacity(n);
         for _ in 0..n {
             vars.push(self.new_var_with_candidates(candidates));
@@ -164,9 +163,12 @@ impl Puzzle {
     /// let mut magic_square = puzzle_solver::Puzzle::new();
     /// magic_square.new_vars_with_candidates_2d(3, 3, &[1,2,3,4,5,6,7,8,9]);
     /// ```
-    pub fn new_vars_with_candidates_2d(self: &mut Puzzle,
-            width: usize, height: usize, candidates: &[Val])
-            -> Vec<Vec<VarToken>> {
+    pub fn new_vars_with_candidates_2d(
+        self: &mut Puzzle,
+        width: usize,
+        height: usize,
+        candidates: &[Val],
+    ) -> Vec<Vec<VarToken>> {
         let mut vars = Vec::with_capacity(height);
         for _ in 0..height {
             vars.push(self.new_vars_with_candidates_1d(width, candidates));
@@ -216,12 +218,11 @@ impl Puzzle {
         let VarToken(idx) = var;
 
         match &self.candidates[idx] {
-            &Candidates::Value(_) =>
-                panic!("attempt to set fixed variable"),
+            &Candidates::Value(_) => panic!("attempt to set fixed variable"),
 
             &Candidates::None => {
                 self.candidates[idx] = Candidates::Set(Rc::new(BTreeSet::new()));
-            },
+            }
 
             &Candidates::Set(_) => (),
         }
@@ -250,8 +251,7 @@ impl Puzzle {
         let VarToken(idx) = var;
 
         match self.candidates[idx] {
-            Candidates::Value(_) =>
-                panic!("attempt to set fixed variable"),
+            Candidates::Value(_) => panic!("attempt to set fixed variable"),
 
             Candidates::None => (),
 
@@ -260,7 +260,7 @@ impl Puzzle {
                 for c in candidates.iter() {
                     cs.remove(c);
                 }
-            },
+            }
         }
     }
 
@@ -281,8 +281,7 @@ impl Puzzle {
         let VarToken(idx) = var;
 
         match self.candidates[idx] {
-            Candidates::Value(_) =>
-                panic!("attempt to set fixed variable"),
+            Candidates::Value(_) => panic!("attempt to set fixed variable"),
 
             Candidates::None => (),
 
@@ -291,13 +290,15 @@ impl Puzzle {
                 let mut set = BTreeSet::new();
                 set.extend(candidates);
                 *cs = cs.intersection(&set).cloned().collect();
-            },
+            }
         }
     }
 
     /// Add a constraint to the puzzle solution.
     pub fn add_constraint<T>(&mut self, constraint: T)
-            where T: Constraint + 'static {
+    where
+        T: Constraint + 'static,
+    {
         self.constraints.push(Rc::new(constraint));
     }
 
@@ -313,7 +314,9 @@ impl Puzzle {
     /// send_more_money.all_different(&vars);
     /// ```
     pub fn all_different<'a, I>(&mut self, vars: I)
-            where I: IntoIterator<Item=&'a VarToken> {
+    where
+        I: IntoIterator<Item = &'a VarToken>,
+    {
         self.add_constraint(constraint::AllDifferent::new(vars));
     }
 
@@ -328,8 +331,11 @@ impl Puzzle {
     ///
     /// magic_square.equals(vars[0][0] + vars[0][1] + vars[0][2], 15);
     /// ```
-    pub fn equals<L,R>(&mut self, lhs: L, rhs: R)
-            where L: Into<LinExpr>, R: Into<LinExpr> {
+    pub fn equals<L, R>(&mut self, lhs: L, rhs: R)
+    where
+        L: Into<LinExpr>,
+        R: Into<LinExpr>,
+    {
         self.add_constraint(constraint::Equality::new(lhs.into() - rhs.into()));
     }
 
@@ -479,8 +485,7 @@ impl PuzzleConstraints {
     }
 
     /// Determine which variables wake up which constraints.
-    fn init_wake(constraints: &Vec<Rc<dyn Constraint>>, num_vars: usize)
-            -> Vec<BitSet> {
+    fn init_wake(constraints: &Vec<Rc<dyn Constraint>>, num_vars: usize) -> Vec<BitSet> {
         let mut wake = vec![BitSet::new(); num_vars];
         for cidx in 0..constraints.len() {
             for &VarToken(idx) in constraints[cidx].vars() {
@@ -498,8 +503,11 @@ impl<'a> PuzzleSearch<'a> {
     /// Allocate a new puzzle searcher.
     fn new(puzzle: &'a Puzzle) -> Self {
         let constraints = PuzzleConstraints::new(puzzle);
-        let vars = puzzle.candidates.iter().map(|cs|
-                VarState::Unassigned(cs.clone())).collect();
+        let vars = puzzle
+            .candidates
+            .iter()
+            .map(|cs| VarState::Unassigned(cs.clone()))
+            .collect();
         let mut wake = BitSet::new();
 
         for cidx in 0..constraints.constraints.len() {
@@ -538,8 +546,7 @@ impl<'a> PuzzleSearch<'a> {
     }
 
     /// Get an iterator over the candidates to an unassigned variable.
-    pub fn get_unassigned(&'a self, var: VarToken)
-            -> Box<dyn Iterator<Item=Val> + 'a> {
+    pub fn get_unassigned(&'a self, var: VarToken) -> Box<dyn Iterator<Item = Val> + 'a> {
         let VarToken(idx) = var;
         match &self.vars[idx] {
             &VarState::Assigned(_) => Box::new(iter::empty()),
@@ -556,19 +563,21 @@ impl<'a> PuzzleSearch<'a> {
             &VarState::Unassigned(ref cs) => match cs {
                 &Candidates::None => Err(()),
                 &Candidates::Value(val) => Ok((val, val)),
-                &Candidates::Set(ref rc) => {
-                    rc.iter().cloned().min().into_iter()
-                        .zip(rc.iter().cloned().max()).next()
-                        .ok_or(())
-                }
+                &Candidates::Set(ref rc) => rc
+                    .iter()
+                    .cloned()
+                    .min()
+                    .into_iter()
+                    .zip(rc.iter().cloned().max())
+                    .next()
+                    .ok_or(()),
             },
             &VarState::Unified(other) => self.get_min_max(other),
         }
     }
 
     /// Set a variable to a value.
-    pub fn set_candidate(&mut self, var: VarToken, val: Val)
-            -> PsResult<()> {
+    pub fn set_candidate(&mut self, var: VarToken, val: Val) -> PsResult<()> {
         let VarToken(idx) = var;
 
         match &self.vars[idx] {
@@ -583,8 +592,7 @@ impl<'a> PuzzleSearch<'a> {
 
         if let &VarState::Unified(other) = &self.vars[idx] {
             self.set_candidate(other, val)
-        } else if let &mut VarState::Unassigned(Candidates::Set(ref mut rc))
-                = &mut self.vars[idx] {
+        } else if let &mut VarState::Unassigned(Candidates::Set(ref mut rc)) = &mut self.vars[idx] {
             if rc.contains(&val) {
                 let mut set = Rc::make_mut(rc);
                 set.clear();
@@ -600,8 +608,7 @@ impl<'a> PuzzleSearch<'a> {
     }
 
     /// Remove a single candidate from a variable.
-    pub fn remove_candidate(&mut self, var: VarToken, val: Val)
-            -> PsResult<()> {
+    pub fn remove_candidate(&mut self, var: VarToken, val: Val) -> PsResult<()> {
         let VarToken(idx) = var;
 
         match &self.vars[idx] {
@@ -616,8 +623,7 @@ impl<'a> PuzzleSearch<'a> {
 
         if let &VarState::Unified(other) = &self.vars[idx] {
             self.remove_candidate(other, val)
-        } else if let &mut VarState::Unassigned(Candidates::Set(ref mut rc))
-                = &mut self.vars[idx] {
+        } else if let &mut VarState::Unassigned(Candidates::Set(ref mut rc)) = &mut self.vars[idx] {
             if rc.contains(&val) {
                 let mut set = Rc::make_mut(rc);
                 set.remove(&val);
@@ -630,25 +636,31 @@ impl<'a> PuzzleSearch<'a> {
     }
 
     /// Bound an variable to the given range.
-    pub fn bound_candidate_range(&mut self, var: VarToken, min: Val, max: Val)
-            -> PsResult<(Val, Val)> {
+    pub fn bound_candidate_range(
+        &mut self,
+        var: VarToken,
+        min: Val,
+        max: Val,
+    ) -> PsResult<(Val, Val)> {
         let VarToken(idx) = var;
 
         match &self.vars[idx] {
-            &VarState::Assigned(v) =>
+            &VarState::Assigned(v) => {
                 if min <= v && v <= max {
-                    return Ok((v, v))
+                    return Ok((v, v));
                 } else {
-                    return Err(())
-                },
+                    return Err(());
+                }
+            }
             &VarState::Unassigned(ref cs) => match cs {
                 &Candidates::None => return Err(()),
-                &Candidates::Value(v) =>
+                &Candidates::Value(v) => {
                     if min <= v && v <= max {
-                        return Ok((v, v))
+                        return Ok((v, v));
                     } else {
-                        return Err(())
-                    },
+                        return Err(());
+                    }
+                }
                 &Candidates::Set(_) => (),
             },
             &VarState::Unified(_) => (),
@@ -656,22 +668,26 @@ impl<'a> PuzzleSearch<'a> {
 
         if let &VarState::Unified(other) = &self.vars[idx] {
             self.bound_candidate_range(other, min, max)
-        } else if let &mut VarState::Unassigned(Candidates::Set(ref mut rc))
-                = &mut self.vars[idx] {
+        } else if let &mut VarState::Unassigned(Candidates::Set(ref mut rc)) = &mut self.vars[idx] {
             let &curr_min = rc.iter().min().expect("candidates");
             let &curr_max = rc.iter().max().expect("candidates");
 
             if curr_min < min || max < curr_max {
                 {
                     let mut set = Rc::make_mut(rc);
-                    *set = set.iter()
+                    *set = set
+                        .iter()
                         .filter(|&val| min <= *val && *val <= max)
                         .cloned()
                         .collect();
                     self.wake.union_with(&self.constraints.wake[idx]);
                 }
-                rc.iter().cloned().min().into_iter()
-                    .zip(rc.iter().cloned().max()).next()
+                rc.iter()
+                    .cloned()
+                    .min()
+                    .into_iter()
+                    .zip(rc.iter().cloned().max())
+                    .next()
                     .ok_or(())
             } else {
                 Ok((curr_min, curr_max))
@@ -687,11 +703,14 @@ impl<'a> PuzzleSearch<'a> {
             return;
         }
 
-        let next_unassigned = self.vars.iter().enumerate().min_by_key(
-                |&(_, vs)| match vs {
-                    &VarState::Unassigned(ref cs) => cs.len(),
-                    _ => ::std::usize::MAX,
-                });
+        let next_unassigned = self
+            .vars
+            .iter()
+            .enumerate()
+            .min_by_key(|&(_, vs)| match vs {
+                &VarState::Unassigned(ref cs) => cs.len(),
+                _ => ::std::usize::MAX,
+            });
 
         if let Some((idx, &VarState::Unassigned(ref cs))) = next_unassigned {
             if cs.len() == 0 {
@@ -716,9 +735,10 @@ impl<'a> PuzzleSearch<'a> {
             }
         } else {
             // No unassigned variables remaining.
-            let vars = (0..self.puzzle.num_vars).map(|idx|
-                    self[VarToken(idx)]).collect();
-            solutions.push(Solution{ vars: vars });
+            let vars = (0..self.puzzle.num_vars)
+                .map(|idx| self[VarToken(idx)])
+                .collect();
+            solutions.push(Solution { vars: vars });
         }
     }
 
@@ -784,8 +804,7 @@ impl<'a> PuzzleSearch<'a> {
     }
 
     /// Unify the "from" variable with the "to" variable.
-    pub fn unify(&mut self, from: VarToken, to: VarToken)
-            -> PsResult<()> {
+    pub fn unify(&mut self, from: VarToken, to: VarToken) -> PsResult<()> {
         if from == to {
             return Ok(());
         }
@@ -796,19 +815,19 @@ impl<'a> PuzzleSearch<'a> {
             let VarToken(search) = from;
             let VarToken(replace) = to;
             match (&self.vars[search], &self.vars[replace]) {
-                (&VarState::Assigned(val1), &VarState::Assigned(val2)) =>
-                    return bool_to_result(val1 == val2),
+                (&VarState::Assigned(val1), &VarState::Assigned(val2)) => {
+                    return bool_to_result(val1 == val2)
+                }
 
                 // Unified variables should have been substituted out previously.
-                (&VarState::Unified(_), _) | (_, &VarState::Unified(_)) =>
-                    panic!("internal representation corrupt"),
+                (&VarState::Unified(_), _) | (_, &VarState::Unified(_)) => {
+                    panic!("internal representation corrupt")
+                }
 
-                (&VarState::Unassigned(_), &VarState::Assigned(_)) =>
-                    (to, from),
+                (&VarState::Unassigned(_), &VarState::Assigned(_)) => (to, from),
 
                 (&VarState::Assigned(_), &VarState::Unassigned(_))
-                | (&VarState::Unassigned(_), &VarState::Unassigned(_)) =>
-                    (from, to),
+                | (&VarState::Unassigned(_), &VarState::Unassigned(_)) => (from, to),
             }
         };
 
@@ -825,9 +844,11 @@ impl<'a> PuzzleSearch<'a> {
         if let &VarState::Assigned(val) = &self.vars[search] {
             r#try!(self.set_candidate(to, val));
         } else {
-            if let (&mut VarState::Unassigned(Candidates::Set(ref mut rc1)),
-                    &mut VarState::Unassigned(Candidates::Set(ref mut rc2)))
-                    = get_two_mut(&mut self.vars, search, replace) {
+            if let (
+                &mut VarState::Unassigned(Candidates::Set(ref mut rc1)),
+                &mut VarState::Unassigned(Candidates::Set(ref mut rc2)),
+            ) = get_two_mut(&mut self.vars, search, replace)
+            {
                 *rc2 = Rc::new(rc2.intersection(rc1).cloned().collect());
                 if rc2.is_empty() {
                     return Err(());
@@ -848,16 +869,16 @@ impl<'a> fmt::Debug for PuzzleSearch<'a> {
             match var {
                 &VarState::Assigned(val) => {
                     write!(f, "  var {}: {}", idx, val)?;
-                },
+                }
                 &VarState::Unassigned(ref cs) => {
                     write!(f, "  var {}:", idx)?;
                     for val in cs.iter() {
                         write!(f, " {}", val)?;
                     }
-                },
+                }
                 &VarState::Unified(VarToken(other)) => {
                     write!(f, "  var {}: var {}", idx, other)?;
-                },
+                }
             }
         }
         write!(f, "}}")?;
@@ -891,8 +912,7 @@ fn bool_to_result(cond: bool) -> PsResult<()> {
     }
 }
 
-fn get_two_mut<'a, T>(slice: &'a mut [T], a: usize, b: usize)
-        -> (&'a mut T, &'a mut T) {
+fn get_two_mut<'a, T>(slice: &'a mut [T], a: usize, b: usize) -> (&'a mut T, &'a mut T) {
     assert!(a != b);
     if a < b {
         let (mut l, mut r) = slice.split_at_mut(b);
diff --git a/tests/hidato.rs b/tests/hidato.rs
index 7f98b94..1860d23 100644
--- a/tests/hidato.rs
+++ b/tests/hidato.rs
@@ -4,7 +4,7 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{Puzzle, Solution, Val, VarToken};
 
 const WIDTH: usize = 8;
 const HEIGHT: usize = 8;
@@ -40,9 +40,15 @@ fn make_hidato(board: &Board) -> (Puzzle, Vec<VarToken>) {
 
     let stride = WIDTH as Val;
     let deltas = [
-        -stride - 1, -stride, -stride + 1,
-        -1, 1,
-        stride - 1, stride, stride + 1 ];
+        -stride - 1,
+        -stride,
+        -stride + 1,
+        -1,
+        1,
+        stride - 1,
+        stride,
+        stride + 1,
+    ];
 
     for i in 1..vars.len() {
         let step = sys.new_var_with_candidates(&deltas);
@@ -84,24 +90,26 @@ fn verify_hidato(dict: &Solution, vars: &Vec<VarToken>, expected: &Board) {
 #[test]
 fn hidato_wikipedia() {
     let puzzle = [
-        [  0, 33, 35,  0,  0, NA, NA, NA ],
-        [  0,  0, 24, 22,  0, NA, NA, NA ],
-        [  0,  0,  0, 21,  0,  0, NA, NA ],
-        [  0, 26,  0, 13, 40, 11, NA, NA ],
-        [ 27,  0,  0,  0,  9,  0,  1, NA ],
-        [ NA, NA,  0,  0, 18,  0,  0, NA ],
-        [ NA, NA, NA, NA,  0,  7,  0,  0 ],
-        [ NA, NA, NA, NA, NA, NA,  5,  0 ] ];
+        [0, 33, 35, 0, 0, NA, NA, NA],
+        [0, 0, 24, 22, 0, NA, NA, NA],
+        [0, 0, 0, 21, 0, 0, NA, NA],
+        [0, 26, 0, 13, 40, 11, NA, NA],
+        [27, 0, 0, 0, 9, 0, 1, NA],
+        [NA, NA, 0, 0, 18, 0, 0, NA],
+        [NA, NA, NA, NA, 0, 7, 0, 0],
+        [NA, NA, NA, NA, NA, NA, 5, 0],
+    ];
 
     let expected = [
-        [ 32, 33, 35, 36, 37, NA, NA, NA ],
-        [ 31, 34, 24, 22, 38, NA, NA, NA ],
-        [ 30, 25, 23, 21, 12, 39, NA, NA ],
-        [ 29, 26, 20, 13, 40, 11, NA, NA ],
-        [ 27, 28, 14, 19,  9, 10,  1, NA ],
-        [ NA, NA, 15, 16, 18,  8,  2, NA ],
-        [ NA, NA, NA, NA, 17,  7,  6,  3 ],
-        [ NA, NA, NA, NA, NA, NA,  5,  4 ] ];
+        [32, 33, 35, 36, 37, NA, NA, NA],
+        [31, 34, 24, 22, 38, NA, NA, NA],
+        [30, 25, 23, 21, 12, 39, NA, NA],
+        [29, 26, 20, 13, 40, 11, NA, NA],
+        [27, 28, 14, 19, 9, 10, 1, NA],
+        [NA, NA, 15, 16, 18, 8, 2, NA],
+        [NA, NA, NA, NA, 17, 7, 6, 3],
+        [NA, NA, NA, NA, NA, NA, 5, 4],
+    ];
 
     let (mut sys, vars) = make_hidato(&puzzle);
     let dict = sys.solve_any().expect("solution");
diff --git a/tests/kakuro.rs b/tests/kakuro.rs
index 84cec7f..2c9e915 100644
--- a/tests/kakuro.rs
+++ b/tests/kakuro.rs
@@ -4,7 +4,7 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{LinExpr,Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{LinExpr, Puzzle, Solution, Val, VarToken};
 
 const SIZE: usize = 7;
 const X: Val = 0;
@@ -12,8 +12,18 @@ type Board = [[Val; SIZE]; SIZE];
 type KakuroVars = Vec<Vec<Option<VarToken>>>;
 
 enum Rule {
-    H{ total: Val, y: usize, x1: usize, x2: usize },
-    V{ total: Val, x: usize, y1: usize, y2: usize },
+    H {
+        total: Val,
+        y: usize,
+        x1: usize,
+        x2: usize,
+    },
+    V {
+        total: Val,
+        x: usize,
+        y1: usize,
+        y2: usize,
+    },
 }
 
 fn make_kakuro(board: &[Rule]) -> (Puzzle, KakuroVars) {
@@ -22,15 +32,15 @@ fn make_kakuro(board: &[Rule]) -> (Puzzle, KakuroVars) {
 
     for rule in board.iter() {
         let (total, x1, y1, x2, y2) = match rule {
-            &Rule::H{total, y, x1, x2} => (total, x1, y, x2, y),
-            &Rule::V{total, x, y1, y2} => (total, x, y1, x, y2),
+            &Rule::H { total, y, x1, x2 } => (total, x1, y, x2, y),
+            &Rule::V { total, x, y1, y2 } => (total, x, y1, x, y2),
         };
 
         let mut vec = Vec::new();
         for y in y1..(y2 + 1) {
             for x in x1..(x2 + 1) {
                 let var = vars[y][x].unwrap_or_else(|| {
-                    let var = sys.new_var_with_candidates(&[1,2,3,4,5,6,7,8,9]);
+                    let var = sys.new_var_with_candidates(&[1, 2, 3, 4, 5, 6, 7, 8, 9]);
                     vars[y][x] = Some(var);
                     var
                 });
@@ -40,7 +50,10 @@ fn make_kakuro(board: &[Rule]) -> (Puzzle, KakuroVars) {
         }
 
         sys.all_different(&vec);
-        sys.equals(total, vec.iter().fold(LinExpr::from(0), |sum, &var| sum + var));
+        sys.equals(
+            total,
+            vec.iter().fold(LinExpr::from(0), |sum, &var| sum + var),
+        );
     }
 
     (sys, vars)
@@ -71,31 +84,161 @@ fn verify_kakuro(dict: &Solution, vars: &KakuroVars, expected: &Board) {
 #[test]
 fn kakuro_wikipedia() {
     let puzzle = [
-        Rule::H{ total:16, y:0, x1:0, x2:1 }, Rule::H{ total:24, y:0, x1:4, x2:6},
-        Rule::H{ total:17, y:1, x1:0, x2:1 }, Rule::H{ total:29, y:1, x1:3, x2:6},
-        Rule::H{ total:35, y:2, x1:0, x2:4 },
-        Rule::H{ total: 7, y:3, x1:1, x2:2 }, Rule::H{ total: 8, y:3, x1:4, x2:5},
-        Rule::H{ total:16, y:4, x1:2, x2:6 },
-        Rule::H{ total:21, y:5, x1:0, x2:3 }, Rule::H{ total: 5, y:5, x1:5, x2:6},
-        Rule::H{ total: 6, y:6, x1:0, x2:2 }, Rule::H{ total: 3, y:6, x1:5, x2:6},
-
-        Rule::V{ total:23, x:0, y1:0, y2:2 }, Rule::V{ total:11, x:0, y1:5, y2:6},
-        Rule::V{ total:30, x:1, y1:0, y2:3 }, Rule::V{ total:10, x:1, y1:5, y2:6},
-        Rule::V{ total:15, x:2, y1:2, y2:6 },
-        Rule::V{ total:17, x:3, y1:1, y2:2 }, Rule::V{ total: 7, x:3, y1:4, y2:5},
-        Rule::V{ total:27, x:4, y1:0, y2:4 },
-        Rule::V{ total:12, x:5, y1:0, y2:1 }, Rule::V{ total:12, x:5, y1:3, y2:6},
-        Rule::V{ total:16, x:6, y1:0, y2:1 }, Rule::V{ total: 7, x:6, y1:4, y2:6},
+        Rule::H {
+            total: 16,
+            y: 0,
+            x1: 0,
+            x2: 1,
+        },
+        Rule::H {
+            total: 24,
+            y: 0,
+            x1: 4,
+            x2: 6,
+        },
+        Rule::H {
+            total: 17,
+            y: 1,
+            x1: 0,
+            x2: 1,
+        },
+        Rule::H {
+            total: 29,
+            y: 1,
+            x1: 3,
+            x2: 6,
+        },
+        Rule::H {
+            total: 35,
+            y: 2,
+            x1: 0,
+            x2: 4,
+        },
+        Rule::H {
+            total: 7,
+            y: 3,
+            x1: 1,
+            x2: 2,
+        },
+        Rule::H {
+            total: 8,
+            y: 3,
+            x1: 4,
+            x2: 5,
+        },
+        Rule::H {
+            total: 16,
+            y: 4,
+            x1: 2,
+            x2: 6,
+        },
+        Rule::H {
+            total: 21,
+            y: 5,
+            x1: 0,
+            x2: 3,
+        },
+        Rule::H {
+            total: 5,
+            y: 5,
+            x1: 5,
+            x2: 6,
+        },
+        Rule::H {
+            total: 6,
+            y: 6,
+            x1: 0,
+            x2: 2,
+        },
+        Rule::H {
+            total: 3,
+            y: 6,
+            x1: 5,
+            x2: 6,
+        },
+        Rule::V {
+            total: 23,
+            x: 0,
+            y1: 0,
+            y2: 2,
+        },
+        Rule::V {
+            total: 11,
+            x: 0,
+            y1: 5,
+            y2: 6,
+        },
+        Rule::V {
+            total: 30,
+            x: 1,
+            y1: 0,
+            y2: 3,
+        },
+        Rule::V {
+            total: 10,
+            x: 1,
+            y1: 5,
+            y2: 6,
+        },
+        Rule::V {
+            total: 15,
+            x: 2,
+            y1: 2,
+            y2: 6,
+        },
+        Rule::V {
+            total: 17,
+            x: 3,
+            y1: 1,
+            y2: 2,
+        },
+        Rule::V {
+            total: 7,
+            x: 3,
+            y1: 4,
+            y2: 5,
+        },
+        Rule::V {
+            total: 27,
+            x: 4,
+            y1: 0,
+            y2: 4,
+        },
+        Rule::V {
+            total: 12,
+            x: 5,
+            y1: 0,
+            y2: 1,
+        },
+        Rule::V {
+            total: 12,
+            x: 5,
+            y1: 3,
+            y2: 6,
+        },
+        Rule::V {
+            total: 16,
+            x: 6,
+            y1: 0,
+            y2: 1,
+        },
+        Rule::V {
+            total: 7,
+            x: 6,
+            y1: 4,
+            y2: 6,
+        },
     ];
 
     let expected = [
-        [ 9, 7, X, X, 8, 7, 9 ],
-        [ 8, 9, X, 8, 9, 5, 7 ],
-        [ 6, 8, 5, 9, 7, X, X ],
-        [ X, 6, 1, X, 2, 6, X ],
-        [ X, X, 4, 6, 1, 3, 2 ],
-        [ 8, 9, 3, 1, X, 1, 4 ],
-        [ 3, 1, 2, X, X, 2, 1 ] ];
+        [9, 7, X, X, 8, 7, 9],
+        [8, 9, X, 8, 9, 5, 7],
+        [6, 8, 5, 9, 7, X, X],
+        [X, 6, 1, X, 2, 6, X],
+        [X, X, 4, 6, 1, 3, 2],
+        [8, 9, 3, 1, X, 1, 4],
+        [3, 1, 2, X, X, 2, 1],
+    ];
 
     let (mut sys, vars) = make_kakuro(&puzzle);
     let dict = sys.solve_any().expect("solution");
diff --git a/tests/killersudoku.rs b/tests/killersudoku.rs
index a897bd0..e8f182e 100644
--- a/tests/killersudoku.rs
+++ b/tests/killersudoku.rs
@@ -4,7 +4,7 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{LinExpr,Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{LinExpr, Puzzle, Solution, Val, VarToken};
 
 const SQRT_SIZE: usize = 3;
 const SIZE: usize = 9;
@@ -13,7 +13,7 @@ type Point = (usize, usize);
 
 fn make_killer_sudoku(board: &[(Val, Vec<Point>)]) -> (Puzzle, Vec<Vec<VarToken>>) {
     let mut sys = Puzzle::new();
-    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1,2,3,4,5,6,7,8,9]);
+    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1, 2, 3, 4, 5, 6, 7, 8, 9]);
 
     for y in 0..SIZE {
         sys.all_different(&vars[y]);
@@ -26,12 +26,16 @@ fn make_killer_sudoku(board: &[(Val, Vec<Point>)]) -> (Puzzle, Vec<Vec<VarToken>
     for block in 0..SIZE {
         let x0 = SQRT_SIZE * (block % SQRT_SIZE);
         let y0 = SQRT_SIZE * (block / SQRT_SIZE);
-        sys.all_different((0..SIZE).map(|n|
-                &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
+        sys.all_different((0..SIZE).map(|n| &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
     }
 
     for &(total, ref points) in board.iter() {
-        sys.equals(total, points.iter().fold(LinExpr::from(0), |sum, &(x,y)| sum + vars[y][x]));
+        sys.equals(
+            total,
+            points
+                .iter()
+                .fold(LinExpr::from(0), |sum, &(x, y)| sum + vars[y][x]),
+        );
     }
 
     (sys, vars)
@@ -44,9 +48,11 @@ fn print_sudoku(dict: &Solution, vars: &Vec<Vec<VarToken>>) {
         }
 
         for x in 0..SIZE {
-            print!("{}{}",
-                   if x % SQRT_SIZE == 0 { " " } else { "" },
-                   dict[vars[y][x]]);
+            print!(
+                "{}{}",
+                if x % SQRT_SIZE == 0 { " " } else { "" },
+                dict[vars[y][x]]
+            );
         }
         println!();
     }
@@ -63,49 +69,48 @@ fn verify_sudoku(dict: &Solution, vars: &Vec<Vec<VarToken>>, expected: &Board) {
 #[test]
 fn killersudoku_wikipedia() {
     let puzzle = [
-        ( 3, vec![(0,0), (1,0)]),
-        (15, vec![(2,0), (3,0), (4,0)]),
-        (22, vec![(5,0), (4,1), (5,1), (4,2)]),
-        ( 4, vec![(6,0), (6,1)]),
-        (16, vec![(7,0), (7,1)]),
-        (15, vec![(8,0), (8,1), (8,2), (8,3)]),
-        (25, vec![(0,1), (1,1), (0,2), (1,2)]),
-        (17, vec![(2,1), (3,1)]),
-        ( 9, vec![(2,2), (3,2), (3,3)]),
-        ( 8, vec![(5,2), (5,3), (5,4)]),
-        (20, vec![(6,2), (7,2), (6,3)]),
-        ( 6, vec![(0,3), (0,4)]),
-        (14, vec![(1,3), (2,3)]),
-        (17, vec![(4,3), (4,4), (4,5)]),
-        (17, vec![(7,3), (6,4), (7,4)]),
-        (13, vec![(1,4), (2,4), (1,5)]),
-        (20, vec![(3,4), (3,5), (3,6)]),
-        (12, vec![(8,4), (8,5)]),
-        (27, vec![(0,5), (0,6), (0,7), (0,8)]),
-        ( 6, vec![(2,5), (1,6), (2,6)]),
-        (20, vec![(5,5), (5,6), (6,6)]),
-        ( 6, vec![(6,5), (7,5)]),
-        (10, vec![(4,6), (3,7), (4,7), (3,8)]),
-        (14, vec![(7,6), (8,6), (7,7), (8,7)]),
-        ( 8, vec![(1,7), (1,8)]),
-        (16, vec![(2,7), (2,8)]),
-        (15, vec![(5,7), (6,7)]),
-        (13, vec![(4,8), (5,8), (6,8)]),
-        (17, vec![(7,8), (8,8)]),
+        (3, vec![(0, 0), (1, 0)]),
+        (15, vec![(2, 0), (3, 0), (4, 0)]),
+        (22, vec![(5, 0), (4, 1), (5, 1), (4, 2)]),
+        (4, vec![(6, 0), (6, 1)]),
+        (16, vec![(7, 0), (7, 1)]),
+        (15, vec![(8, 0), (8, 1), (8, 2), (8, 3)]),
+        (25, vec![(0, 1), (1, 1), (0, 2), (1, 2)]),
+        (17, vec![(2, 1), (3, 1)]),
+        (9, vec![(2, 2), (3, 2), (3, 3)]),
+        (8, vec![(5, 2), (5, 3), (5, 4)]),
+        (20, vec![(6, 2), (7, 2), (6, 3)]),
+        (6, vec![(0, 3), (0, 4)]),
+        (14, vec![(1, 3), (2, 3)]),
+        (17, vec![(4, 3), (4, 4), (4, 5)]),
+        (17, vec![(7, 3), (6, 4), (7, 4)]),
+        (13, vec![(1, 4), (2, 4), (1, 5)]),
+        (20, vec![(3, 4), (3, 5), (3, 6)]),
+        (12, vec![(8, 4), (8, 5)]),
+        (27, vec![(0, 5), (0, 6), (0, 7), (0, 8)]),
+        (6, vec![(2, 5), (1, 6), (2, 6)]),
+        (20, vec![(5, 5), (5, 6), (6, 6)]),
+        (6, vec![(6, 5), (7, 5)]),
+        (10, vec![(4, 6), (3, 7), (4, 7), (3, 8)]),
+        (14, vec![(7, 6), (8, 6), (7, 7), (8, 7)]),
+        (8, vec![(1, 7), (1, 8)]),
+        (16, vec![(2, 7), (2, 8)]),
+        (15, vec![(5, 7), (6, 7)]),
+        (13, vec![(4, 8), (5, 8), (6, 8)]),
+        (17, vec![(7, 8), (8, 8)]),
     ];
 
     let expected = [
-        [ 2,1,5,  6,4,7,  3,9,8 ],
-        [ 3,6,8,  9,5,2,  1,7,4 ],
-        [ 7,9,4,  3,8,1,  6,5,2 ],
-
-        [ 5,8,6,  2,7,4,  9,3,1 ],
-        [ 1,4,2,  5,9,3,  8,6,7 ],
-        [ 9,7,3,  8,1,6,  4,2,5 ],
-
-        [ 8,2,1,  7,3,9,  5,4,6 ],
-        [ 6,5,9,  4,2,8,  7,1,3 ],
-        [ 4,3,7,  1,6,5,  2,8,9 ] ];
+        [2, 1, 5, 6, 4, 7, 3, 9, 8],
+        [3, 6, 8, 9, 5, 2, 1, 7, 4],
+        [7, 9, 4, 3, 8, 1, 6, 5, 2],
+        [5, 8, 6, 2, 7, 4, 9, 3, 1],
+        [1, 4, 2, 5, 9, 3, 8, 6, 7],
+        [9, 7, 3, 8, 1, 6, 4, 2, 5],
+        [8, 2, 1, 7, 3, 9, 5, 4, 6],
+        [6, 5, 9, 4, 2, 8, 7, 1, 3],
+        [4, 3, 7, 1, 6, 5, 2, 8, 9],
+    ];
 
     let (mut sys, vars) = make_killer_sudoku(&puzzle);
     let dict = sys.solve_any().expect("solution");
diff --git a/tests/magicsquare.rs b/tests/magicsquare.rs
index 096f582..97bf440 100644
--- a/tests/magicsquare.rs
+++ b/tests/magicsquare.rs
@@ -4,7 +4,7 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{LinExpr,Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{LinExpr, Puzzle, Solution, Val, VarToken};
 
 fn make_magic_square(n: usize) -> (Puzzle, Vec<Vec<VarToken>>, VarToken) {
     let mut sys = Puzzle::new();
@@ -19,16 +19,28 @@ fn make_magic_square(n: usize) -> (Puzzle, Vec<Vec<VarToken>>, VarToken) {
     sys.all_different(vars.iter().flat_map(|it| it));
 
     for y in 0..n {
-        sys.equals(total, vars[y].iter().fold(LinExpr::from(0), |sum, &x| sum + x));
+        sys.equals(
+            total,
+            vars[y].iter().fold(LinExpr::from(0), |sum, &x| sum + x),
+        );
     }
 
     for x in 0..n {
-        sys.equals(total, vars.iter().fold(LinExpr::from(0), |sum, row| sum + row[x]));
+        sys.equals(
+            total,
+            vars.iter().fold(LinExpr::from(0), |sum, row| sum + row[x]),
+        );
     }
 
     {
-        sys.equals(total, (0..n).fold(LinExpr::from(0), |sum, i| sum + vars[i][i]));
-        sys.equals(total, (0..n).fold(LinExpr::from(0), |sum, i| sum + vars[i][n - i - 1]));
+        sys.equals(
+            total,
+            (0..n).fold(LinExpr::from(0), |sum, i| sum + vars[i][i]),
+        );
+        sys.equals(
+            total,
+            (0..n).fold(LinExpr::from(0), |sum, i| sum + vars[i][n - i - 1]),
+        );
     }
 
     // Sum of all digits = sum of all rows (columns) = total * n.
diff --git a/tests/nonogram.rs b/tests/nonogram.rs
index 5987fd7..224f84c 100644
--- a/tests/nonogram.rs
+++ b/tests/nonogram.rs
@@ -4,9 +4,9 @@
 
 extern crate puzzle_solver;
 
+use puzzle_solver::*;
 use std::collections::HashMap;
 use std::rc::Rc;
-use puzzle_solver::*;
 
 const WIDTH: usize = 20;
 const HEIGHT: usize = 20;
@@ -23,7 +23,7 @@ struct Nonogram {
     rule: Vec<usize>,
 }
 
-#[derive(Clone,Copy)]
+#[derive(Clone, Copy)]
 enum AutoFillResult {
     // Too many solutions, no need to find any more
     SearchEnded,
@@ -45,11 +45,14 @@ impl Nonogram {
         }
     }
 
-    fn autofill(&self,
-            trial: &mut Vec<Val>, pos: usize, rule_idx: usize,
-            accum: &mut Vec<Val>,
-            cache: &mut HashMap<(usize, usize), AutoFillResult>)
-            -> AutoFillResult {
+    fn autofill(
+        &self,
+        trial: &mut Vec<Val>,
+        pos: usize,
+        rule_idx: usize,
+        accum: &mut Vec<Val>,
+        cache: &mut HashMap<(usize, usize), AutoFillResult>,
+    ) -> AutoFillResult {
         assert!(pos <= trial.len() && rule_idx <= self.rule.len());
         let key = (pos, rule_idx);
 
@@ -65,8 +68,10 @@ impl Nonogram {
                 *a = *a | *t;
             }
 
-            if accum.iter().all(|&t|
-                    t < FLAG_UNKNOWN || t == FLAG_UNKNOWN | FLAG_ON | FLAG_OFF) {
+            if accum
+                .iter()
+                .all(|&t| t < FLAG_UNKNOWN || t == FLAG_UNKNOWN | FLAG_ON | FLAG_OFF)
+            {
                 return AutoFillResult::SearchEnded;
             }
 
@@ -75,9 +80,8 @@ impl Nonogram {
 
         // Not enough space.
         if rule_idx < self.rule.len() {
-            let required_space
-                = self.rule[rule_idx..].iter().sum::<usize>()
-                + (self.rule.len() - rule_idx - 1);
+            let required_space =
+                self.rule[rule_idx..].iter().sum::<usize>() + (self.rule.len() - rule_idx - 1);
 
             if pos + required_space > trial.len() {
                 return AutoFillResult::Conflict;
@@ -93,16 +97,17 @@ impl Nonogram {
             }
 
             match self.autofill(trial, pos + 1, rule_idx, accum, cache) {
-                res@AutoFillResult::SearchEnded => return res,
-                res@AutoFillResult::SolutionFound => result = res,
+                res @ AutoFillResult::SearchEnded => return res,
+                res @ AutoFillResult::SolutionFound => result = res,
                 AutoFillResult::Conflict => (),
             }
         }
 
         // Try filled.
         if trial[pos] != FLAG_OFF
-                && rule_idx < self.rule.len()
-                && pos + self.rule[rule_idx] <= trial.len() {
+            && rule_idx < self.rule.len()
+            && pos + self.rule[rule_idx] <= trial.len()
+        {
             let mut ok = true;
             let mut pos = pos;
 
@@ -127,8 +132,8 @@ impl Nonogram {
 
             if ok {
                 match self.autofill(trial, pos, rule_idx + 1, accum, cache) {
-                    res@AutoFillResult::SearchEnded => return res,
-                    res@AutoFillResult::SolutionFound => result = res,
+                    res @ AutoFillResult::SearchEnded => return res,
+                    res @ AutoFillResult::SolutionFound => result = res,
                     AutoFillResult::Conflict => (),
                 }
             }
@@ -140,7 +145,7 @@ impl Nonogram {
 }
 
 impl Constraint for Nonogram {
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a> {
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a> {
         Box::new(self.vars.iter())
     }
 
@@ -159,32 +164,31 @@ impl Constraint for Nonogram {
         match self.autofill(&mut trial, 0, 0, &mut accum, &mut cache) {
             AutoFillResult::Conflict => return Err(()),
             AutoFillResult::SearchEnded => (),
-            AutoFillResult::SolutionFound =>
+            AutoFillResult::SolutionFound => {
                 for idx in 0..self.vars.len() {
                     if accum[idx] == FLAG_UNKNOWN | FLAG_OFF {
                         r#try!(search.set_candidate(self.vars[idx], 0));
                     } else if accum[idx] == FLAG_UNKNOWN | FLAG_ON {
                         r#try!(search.set_candidate(self.vars[idx], 1));
                     }
-                },
+                }
+            }
         }
 
         Ok(())
     }
 
-    fn substitute(&self, _search: VarToken, _replace: VarToken)
-            -> PsResult<Rc<dyn Constraint>> {
+    fn substitute(&self, _search: VarToken, _replace: VarToken) -> PsResult<Rc<dyn Constraint>> {
         unimplemented!();
     }
 }
 
 /*--------------------------------------------------------------*/
 
-fn make_nonogram(rows: &[Vec<usize>], cols: &[Vec<usize>])
-        -> (Puzzle, Vec<Vec<VarToken>>) {
+fn make_nonogram(rows: &[Vec<usize>], cols: &[Vec<usize>]) -> (Puzzle, Vec<Vec<VarToken>>) {
     let mut sys = Puzzle::new();
     let (w, h) = (cols.len(), rows.len());
-    let vars = sys.new_vars_with_candidates_2d(w, h, &[0,1]);
+    let vars = sys.new_vars_with_candidates_2d(w, h, &[0, 1]);
 
     for y in 0..h {
         sys.add_constraint(Nonogram::new(&vars[y], &rows[y]));
@@ -192,8 +196,9 @@ fn make_nonogram(rows: &[Vec<usize>], cols: &[Vec<usize>])
 
     for x in 0..w {
         sys.add_constraint(Nonogram::new(
-                &vars.iter().map(|row| row[x]).collect(),
-                &cols[x]));
+            &vars.iter().map(|row| row[x]).collect(),
+            &cols[x],
+        ));
     }
 
     (sys, vars)
@@ -221,73 +226,71 @@ fn nonogram_wikipedia() {
     let puzzle_rows = [
         vec![3],
         vec![5],
-        vec![3,1],
-        vec![2,1],
-        vec![3,3,4],
-        vec![2,2,7],
-        vec![6,1,1],
-        vec![4,2,2],
-        vec![1,1],
-        vec![3,1],
+        vec![3, 1],
+        vec![2, 1],
+        vec![3, 3, 4],
+        vec![2, 2, 7],
+        vec![6, 1, 1],
+        vec![4, 2, 2],
+        vec![1, 1],
+        vec![3, 1],
         vec![6],
-        vec![2,7],
-        vec![6,3,1],
-        vec![1,2,2,1,1],
-        vec![4,1,1,3],
-        vec![4,2,2],
-        vec![3,3,1],
-        vec![3,3],
+        vec![2, 7],
+        vec![6, 3, 1],
+        vec![1, 2, 2, 1, 1],
+        vec![4, 1, 1, 3],
+        vec![4, 2, 2],
+        vec![3, 3, 1],
+        vec![3, 3],
         vec![3],
-        vec![2,1],
+        vec![2, 1],
     ];
 
     let puzzle_cols = [
         vec![2],
-        vec![1,2],
-        vec![2,3],
-        vec![2,3],
-        vec![3,1,1],
-        vec![2,1,1],
-        vec![1,1,1,2,2],
-        vec![1,1,3,1,3],
-        vec![2,6,4],
-        vec![3,3,9,1],
-        vec![5,3,2],
-        vec![3,1,2,2],
-        vec![2,1,7],
-        vec![3,3,2],
-        vec![2,4],
-        vec![2,1,2],
-        vec![2,2,1],
-        vec![2,2],
+        vec![1, 2],
+        vec![2, 3],
+        vec![2, 3],
+        vec![3, 1, 1],
+        vec![2, 1, 1],
+        vec![1, 1, 1, 2, 2],
+        vec![1, 1, 3, 1, 3],
+        vec![2, 6, 4],
+        vec![3, 3, 9, 1],
+        vec![5, 3, 2],
+        vec![3, 1, 2, 2],
+        vec![2, 1, 7],
+        vec![3, 3, 2],
+        vec![2, 4],
+        vec![2, 1, 2],
+        vec![2, 2, 1],
+        vec![2, 2],
         vec![1],
         vec![1],
     ];
 
     let expected = [
-        [ 0,0,0,0,0,  0,0,0,0,0,  1,1,1,0,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,0,0,0,1,  1,1,1,1,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,0,0,0,1,  1,1,0,1,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,0,0,0,1,  1,0,0,1,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,1,1,1,0,  1,1,1,0,1,  1,1,1,0,0 ],
-
-        [ 0,0,0,0,1,  1,0,0,1,1,  0,0,0,1,1,  1,1,1,1,1 ],
-        [ 0,0,1,1,1,  1,1,1,0,1,  0,0,0,1,0,  0,0,0,0,0 ],
-        [ 0,1,1,1,1,  0,0,0,1,1,  0,0,1,1,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,0,0,1,0,  0,0,1,0,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,0,1,1,1,  0,0,1,0,0,  0,0,0,0,0 ],
-
-        [ 0,0,0,0,0,  0,0,1,1,1,  1,1,1,0,0,  0,0,0,0,0 ],
-        [ 0,1,1,0,0,  0,1,1,1,1,  1,1,1,0,0,  0,0,0,0,0 ],
-        [ 1,1,1,1,1,  1,0,0,1,1,  1,0,1,0,0,  0,0,0,0,0 ],
-        [ 1,0,1,1,0,  0,1,1,0,1,  0,0,1,0,0,  0,0,0,0,0 ],
-        [ 0,0,0,1,1,  1,1,0,0,1,  0,1,0,0,1,  1,1,0,0,0 ],
-
-        [ 0,0,0,0,0,  0,0,0,1,1,  1,1,0,1,1,  0,1,1,0,0 ],
-        [ 0,0,0,0,0,  0,0,0,1,1,  1,0,0,1,1,  1,0,1,0,0 ],
-        [ 0,0,0,0,0,  0,0,1,1,1,  0,0,0,0,1,  1,1,0,0,0 ],
-        [ 0,0,0,0,0,  0,1,1,1,0,  0,0,0,0,0,  0,0,0,0,0 ],
-        [ 0,0,0,0,0,  0,1,1,0,1,  0,0,0,0,0,  0,0,0,0,0 ] ];
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 0],
+        [0, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1],
+        [0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0],
+        [0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0],
+        [0, 1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0],
+        [1, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0],
+        [1, 0, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0],
+        [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+        [0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+    ];
 
     let (mut sys, vars) = make_nonogram(&puzzle_rows, &puzzle_cols);
     let dict = sys.solve_unique().expect("solution");
diff --git a/tests/queens.rs b/tests/queens.rs
index 9a5b2dd..bedd489 100644
--- a/tests/queens.rs
+++ b/tests/queens.rs
@@ -4,21 +4,24 @@
 
 extern crate puzzle_solver;
 
-use std::rc::Rc;
 use puzzle_solver::*;
+use std::rc::Rc;
 
 struct NoDiagonal {
     vars: Vec<VarToken>,
 }
 
 impl Constraint for NoDiagonal {
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a> {
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a> {
         Box::new(self.vars.iter())
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val)
-            -> PsResult<()> {
-        let y1 = self.vars.iter().position(|&v| v == var).expect("unreachable");
+    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
+        let y1 = self
+            .vars
+            .iter()
+            .position(|&v| v == var)
+            .expect("unreachable");
         for (y2, &var2) in self.vars.iter().enumerate() {
             if !search.is_assigned(var2) {
                 let x1 = val;
@@ -31,8 +34,7 @@ impl Constraint for NoDiagonal {
         Ok(())
     }
 
-    fn substitute(&self, _from: VarToken, _to: VarToken)
-            -> PsResult<Rc<dyn Constraint>> {
+    fn substitute(&self, _from: VarToken, _to: VarToken) -> PsResult<Rc<dyn Constraint>> {
         unimplemented!();
     }
 }
@@ -43,7 +45,7 @@ fn make_queens(n: usize) -> (Puzzle, Vec<VarToken>) {
     let vars = sys.new_vars_with_candidates_1d(n, &pos);
 
     sys.all_different(&vars);
-    sys.add_constraint(NoDiagonal{ vars: vars.clone() });
+    sys.add_constraint(NoDiagonal { vars: vars.clone() });
     (sys, vars)
 }
 
diff --git a/tests/samuraisudoku.rs b/tests/samuraisudoku.rs
index 2380fea..a8a9879 100644
--- a/tests/samuraisudoku.rs
+++ b/tests/samuraisudoku.rs
@@ -5,7 +5,7 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{Puzzle, Solution, Val, VarToken};
 
 const SQRT_SIZE: usize = 3;
 const SIZE: usize = 9;
@@ -15,7 +15,7 @@ type SudokuVars = Vec<Vec<VarToken>>;
 type SamuraiVars = (SudokuVars, SudokuVars, SudokuVars, SudokuVars, SudokuVars);
 
 fn make_sudoku(sys: &mut Puzzle) -> SudokuVars {
-    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1,2,3,4,5,6,7,8,9]);
+    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1, 2, 3, 4, 5, 6, 7, 8, 9]);
 
     for y in 0..SIZE {
         sys.all_different(&vars[y]);
@@ -28,15 +28,18 @@ fn make_sudoku(sys: &mut Puzzle) -> SudokuVars {
     for block in 0..SIZE {
         let x0 = SQRT_SIZE * (block % SQRT_SIZE);
         let y0 = SQRT_SIZE * (block / SQRT_SIZE);
-        sys.all_different((0..SIZE).map(|n|
-                &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
+        sys.all_different((0..SIZE).map(|n| &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
     }
 
     vars
 }
 
 fn make_samurai_sudoku(board: &Board) -> (Puzzle, SamuraiVars) {
-    let set = |sys: &mut Puzzle, var, val| if val != 0 { sys.set_value(var, val) };
+    let set = |sys: &mut Puzzle, var, val| {
+        if val != 0 {
+            sys.set_value(var, val)
+        }
+    };
 
     let mut sys = Puzzle::new();
     let tl = make_sudoku(&mut sys);
@@ -47,10 +50,22 @@ fn make_samurai_sudoku(board: &Board) -> (Puzzle, SamuraiVars) {
 
     for y in 0..SQRT_SIZE {
         for x in 0..SQRT_SIZE {
-            sys.unify(mid[0 * SQRT_SIZE + y][0 * SQRT_SIZE + x], tl[2 * SQRT_SIZE + y][2 * SQRT_SIZE + x]);
-            sys.unify(mid[0 * SQRT_SIZE + y][2 * SQRT_SIZE + x], tr[2 * SQRT_SIZE + y][0 * SQRT_SIZE + x]);
-            sys.unify(mid[2 * SQRT_SIZE + y][0 * SQRT_SIZE + x], bl[0 * SQRT_SIZE + y][2 * SQRT_SIZE + x]);
-            sys.unify(mid[2 * SQRT_SIZE + y][2 * SQRT_SIZE + x], br[0 * SQRT_SIZE + y][0 * SQRT_SIZE + x]);
+            sys.unify(
+                mid[0 * SQRT_SIZE + y][0 * SQRT_SIZE + x],
+                tl[2 * SQRT_SIZE + y][2 * SQRT_SIZE + x],
+            );
+            sys.unify(
+                mid[0 * SQRT_SIZE + y][2 * SQRT_SIZE + x],
+                tr[2 * SQRT_SIZE + y][0 * SQRT_SIZE + x],
+            );
+            sys.unify(
+                mid[2 * SQRT_SIZE + y][0 * SQRT_SIZE + x],
+                bl[0 * SQRT_SIZE + y][2 * SQRT_SIZE + x],
+            );
+            sys.unify(
+                mid[2 * SQRT_SIZE + y][2 * SQRT_SIZE + x],
+                br[0 * SQRT_SIZE + y][0 * SQRT_SIZE + x],
+            );
         }
     }
 
@@ -59,8 +74,16 @@ fn make_samurai_sudoku(board: &Board) -> (Puzzle, SamuraiVars) {
             set(&mut sys, tl[y][x], board[y][x]);
             set(&mut sys, tr[y][x], board[y][SIZE + SQRT_SIZE + x]);
             set(&mut sys, bl[y][x], board[SIZE + SQRT_SIZE + y][x]);
-            set(&mut sys, br[y][x], board[SIZE + SQRT_SIZE + y][SIZE + SQRT_SIZE + x]);
-            set(&mut sys, mid[y][x], board[2 * SQRT_SIZE + y][2 * SQRT_SIZE + x]);
+            set(
+                &mut sys,
+                br[y][x],
+                board[SIZE + SQRT_SIZE + y][SIZE + SQRT_SIZE + x],
+            );
+            set(
+                &mut sys,
+                mid[y][x],
+                board[2 * SQRT_SIZE + y][2 * SQRT_SIZE + x],
+            );
         }
     }
 
@@ -70,7 +93,11 @@ fn make_samurai_sudoku(board: &Board) -> (Puzzle, SamuraiVars) {
 fn print_samurai_sudoku(dict: &Solution, vars: &SamuraiVars) {
     let &(ref tl, ref tr, ref bl, ref br, ref mid) = vars;
     let pr3 = |a: &[VarToken], j| print!(" {}{}{}", dict[a[j]], dict[a[j + 1]], dict[a[j + 2]]);
-    let pr9 = |a| { pr3(a, 0); pr3(a, 3); pr3(a, 6); };
+    let pr9 = |a| {
+        pr3(a, 0);
+        pr3(a, 3);
+        pr3(a, 6);
+    };
     let gap = || print!("    ");
 
     for i in 0..SIZE {
@@ -110,8 +137,14 @@ fn verify_samurai_sudoku(dict: &Solution, vars: &SamuraiVars, expected: &Board)
             assert_eq!(dict[tl[i][j]], expected[i][j]);
             assert_eq!(dict[tr[i][j]], expected[i][SIZE + SQRT_SIZE + j]);
             assert_eq!(dict[bl[i][j]], expected[SIZE + SQRT_SIZE + i][j]);
-            assert_eq!(dict[br[i][j]], expected[SIZE + SQRT_SIZE + i][SIZE + SQRT_SIZE + j]);
-            assert_eq!(dict[mid[i][j]], expected[2 * SQRT_SIZE + i][2 * SQRT_SIZE + j]);
+            assert_eq!(
+                dict[br[i][j]],
+                expected[SIZE + SQRT_SIZE + i][SIZE + SQRT_SIZE + j]
+            );
+            assert_eq!(
+                dict[mid[i][j]],
+                expected[2 * SQRT_SIZE + i][2 * SQRT_SIZE + j]
+            );
         }
     }
 }
@@ -119,62 +152,136 @@ fn verify_samurai_sudoku(dict: &Solution, vars: &SamuraiVars, expected: &Board)
 #[test]
 fn samuraisudoku_easy() {
     let puzzle = [
-        [ 0,0,3,  0,0,0,  2,0,0,  X,X,X,  0,0,6,  0,0,0,  2,0,0 ],
-        [ 0,2,0,  4,0,8,  0,3,0,  X,X,X,  0,3,0,  4,0,2,  0,8,0 ],
-        [ 8,0,0,  0,9,0,  0,0,4,  X,X,X,  8,0,0,  0,1,0,  0,0,4 ],
-
-        [ 0,5,0,  6,0,1,  0,2,0,  X,X,X,  0,2,0,  1,0,7,  0,9,0 ],
-        [ 0,0,8,  0,0,0,  6,0,0,  X,X,X,  0,0,9,  0,0,0,  8,0,0 ],
-        [ 0,7,0,  8,0,4,  0,1,0,  X,X,X,  0,8,0,  5,0,9,  0,4,0 ],
-
-        [ 1,0,0,  0,7,0,  0,0,0,  0,0,0,  0,0,0,  0,7,0,  0,0,5 ],
-        [ 0,4,0,  1,0,2,  0,0,0,  0,0,0,  0,0,0,  2,0,8,  0,7,0 ],
-        [ 0,0,9,  0,0,0,  0,0,0,  0,6,0,  0,0,0,  0,0,0,  1,0,0 ],
-
-        [ X,X,X,  X,X,X,  0,0,0,  5,0,1,  0,0,0,  X,X,X,  X,X,X ],
-        [ X,X,X,  X,X,X,  0,0,9,  0,0,0,  6,0,0,  X,X,X,  X,X,X ],
-        [ X,X,X,  X,X,X,  0,0,0,  3,0,6,  0,0,0,  X,X,X,  X,X,X ],
-
-        [ 0,0,8,  0,0,0,  0,0,0,  0,7,0,  0,0,0,  0,0,0,  4,0,0 ],
-        [ 0,4,0,  5,0,1,  0,0,0,  0,0,0,  0,0,0,  9,0,5,  0,7,0 ],
-        [ 6,0,0,  0,2,0,  0,0,0,  0,0,0,  0,0,0,  0,6,0,  0,0,9 ],
-
-        [ 0,9,0,  1,0,3,  0,7,0,  X,X,X,  0,7,0,  5,0,1,  0,9,0 ],
-        [ 0,0,5,  0,0,0,  1,0,0,  X,X,X,  0,0,3,  0,0,0,  6,0,0 ],
-        [ 0,1,0,  6,0,8,  0,9,0,  X,X,X,  0,2,0,  8,0,6,  0,1,0 ],
-
-        [ 5,0,0,  0,7,0,  0,0,6,  X,X,X,  7,0,0,  0,2,0,  0,0,5 ],
-        [ 0,2,0,  3,0,5,  0,1,0,  X,X,X,  0,9,0,  6,0,4,  0,3,0 ],
-        [ 0,0,6,  0,0,0,  2,0,0,  X,X,X,  0,0,4,  0,0,0,  1,0,0 ] ];
+        [
+            0, 0, 3, 0, 0, 0, 2, 0, 0, X, X, X, 0, 0, 6, 0, 0, 0, 2, 0, 0,
+        ],
+        [
+            0, 2, 0, 4, 0, 8, 0, 3, 0, X, X, X, 0, 3, 0, 4, 0, 2, 0, 8, 0,
+        ],
+        [
+            8, 0, 0, 0, 9, 0, 0, 0, 4, X, X, X, 8, 0, 0, 0, 1, 0, 0, 0, 4,
+        ],
+        [
+            0, 5, 0, 6, 0, 1, 0, 2, 0, X, X, X, 0, 2, 0, 1, 0, 7, 0, 9, 0,
+        ],
+        [
+            0, 0, 8, 0, 0, 0, 6, 0, 0, X, X, X, 0, 0, 9, 0, 0, 0, 8, 0, 0,
+        ],
+        [
+            0, 7, 0, 8, 0, 4, 0, 1, 0, X, X, X, 0, 8, 0, 5, 0, 9, 0, 4, 0,
+        ],
+        [
+            1, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 5,
+        ],
+        [
+            0, 4, 0, 1, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 8, 0, 7, 0,
+        ],
+        [
+            0, 0, 9, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0,
+        ],
+        [
+            X, X, X, X, X, X, 0, 0, 0, 5, 0, 1, 0, 0, 0, X, X, X, X, X, X,
+        ],
+        [
+            X, X, X, X, X, X, 0, 0, 9, 0, 0, 0, 6, 0, 0, X, X, X, X, X, X,
+        ],
+        [
+            X, X, X, X, X, X, 0, 0, 0, 3, 0, 6, 0, 0, 0, X, X, X, X, X, X,
+        ],
+        [
+            0, 0, 8, 0, 0, 0, 0, 0, 0, 0, 7, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0,
+        ],
+        [
+            0, 4, 0, 5, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 9, 0, 5, 0, 7, 0,
+        ],
+        [
+            6, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 6, 0, 0, 0, 9,
+        ],
+        [
+            0, 9, 0, 1, 0, 3, 0, 7, 0, X, X, X, 0, 7, 0, 5, 0, 1, 0, 9, 0,
+        ],
+        [
+            0, 0, 5, 0, 0, 0, 1, 0, 0, X, X, X, 0, 0, 3, 0, 0, 0, 6, 0, 0,
+        ],
+        [
+            0, 1, 0, 6, 0, 8, 0, 9, 0, X, X, X, 0, 2, 0, 8, 0, 6, 0, 1, 0,
+        ],
+        [
+            5, 0, 0, 0, 7, 0, 0, 0, 6, X, X, X, 7, 0, 0, 0, 2, 0, 0, 0, 5,
+        ],
+        [
+            0, 2, 0, 3, 0, 5, 0, 1, 0, X, X, X, 0, 9, 0, 6, 0, 4, 0, 3, 0,
+        ],
+        [
+            0, 0, 6, 0, 0, 0, 2, 0, 0, X, X, X, 0, 0, 4, 0, 0, 0, 1, 0, 0,
+        ],
+    ];
 
     let expected = [
-        [ 4,9,3,  7,1,5,  2,6,8,  X,X,X,  9,4,6,  8,3,5,  2,1,7 ],
-        [ 5,2,7,  4,6,8,  9,3,1,  X,X,X,  1,3,7,  4,9,2,  5,8,6 ],
-        [ 8,6,1,  2,9,3,  5,7,4,  X,X,X,  8,5,2,  7,1,6,  9,3,4 ],
-
-        [ 9,5,4,  6,3,1,  8,2,7,  X,X,X,  5,2,4,  1,8,7,  6,9,3 ],
-        [ 3,1,8,  9,2,7,  6,4,5,  X,X,X,  7,1,9,  6,4,3,  8,5,2 ],
-        [ 2,7,6,  8,5,4,  3,1,9,  X,X,X,  6,8,3,  5,2,9,  7,4,1 ],
-
-        [ 1,8,2,  3,7,9,  4,5,6,  7,1,3,  2,9,8,  3,7,1,  4,6,5 ],
-        [ 6,4,5,  1,8,2,  7,9,3,  8,5,2,  4,6,1,  2,5,8,  3,7,9 ],
-        [ 7,3,9,  5,4,6,  1,8,2,  9,6,4,  3,7,5,  9,6,4,  1,2,8 ],
-
-        [ X,X,X,  X,X,X,  6,4,8,  5,9,1,  7,2,3,  X,X,X,  X,X,X ],
-        [ X,X,X,  X,X,X,  3,1,9,  2,8,7,  6,5,4,  X,X,X,  X,X,X ],
-        [ X,X,X,  X,X,X,  2,7,5,  3,4,6,  1,8,9,  X,X,X,  X,X,X ],
-
-        [ 1,7,8,  9,3,6,  5,2,4,  1,7,8,  9,3,6,  2,8,7,  4,5,1 ],
-        [ 2,4,3,  5,8,1,  9,6,7,  4,3,5,  8,1,2,  9,4,5,  3,7,6 ],
-        [ 6,5,9,  4,2,7,  8,3,1,  6,2,9,  5,4,7,  1,6,3,  8,2,9 ],
-
-        [ 8,9,2,  1,4,3,  6,7,5,  X,X,X,  6,7,8,  5,3,1,  2,9,4 ],
-        [ 4,6,5,  7,9,2,  1,8,3,  X,X,X,  1,5,3,  4,9,2,  6,8,7 ],
-        [ 3,1,7,  6,5,8,  4,9,2,  X,X,X,  4,2,9,  8,7,6,  5,1,3 ],
-
-        [ 5,8,1,  2,7,9,  3,4,6,  X,X,X,  7,6,1,  3,2,8,  9,4,5 ],
-        [ 9,2,4,  3,6,5,  7,1,8,  X,X,X,  2,9,5,  6,1,4,  7,3,8 ],
-        [ 7,3,6,  8,1,4,  2,5,9,  X,X,X,  3,8,4,  7,5,9,  1,6,2 ] ];
+        [
+            4, 9, 3, 7, 1, 5, 2, 6, 8, X, X, X, 9, 4, 6, 8, 3, 5, 2, 1, 7,
+        ],
+        [
+            5, 2, 7, 4, 6, 8, 9, 3, 1, X, X, X, 1, 3, 7, 4, 9, 2, 5, 8, 6,
+        ],
+        [
+            8, 6, 1, 2, 9, 3, 5, 7, 4, X, X, X, 8, 5, 2, 7, 1, 6, 9, 3, 4,
+        ],
+        [
+            9, 5, 4, 6, 3, 1, 8, 2, 7, X, X, X, 5, 2, 4, 1, 8, 7, 6, 9, 3,
+        ],
+        [
+            3, 1, 8, 9, 2, 7, 6, 4, 5, X, X, X, 7, 1, 9, 6, 4, 3, 8, 5, 2,
+        ],
+        [
+            2, 7, 6, 8, 5, 4, 3, 1, 9, X, X, X, 6, 8, 3, 5, 2, 9, 7, 4, 1,
+        ],
+        [
+            1, 8, 2, 3, 7, 9, 4, 5, 6, 7, 1, 3, 2, 9, 8, 3, 7, 1, 4, 6, 5,
+        ],
+        [
+            6, 4, 5, 1, 8, 2, 7, 9, 3, 8, 5, 2, 4, 6, 1, 2, 5, 8, 3, 7, 9,
+        ],
+        [
+            7, 3, 9, 5, 4, 6, 1, 8, 2, 9, 6, 4, 3, 7, 5, 9, 6, 4, 1, 2, 8,
+        ],
+        [
+            X, X, X, X, X, X, 6, 4, 8, 5, 9, 1, 7, 2, 3, X, X, X, X, X, X,
+        ],
+        [
+            X, X, X, X, X, X, 3, 1, 9, 2, 8, 7, 6, 5, 4, X, X, X, X, X, X,
+        ],
+        [
+            X, X, X, X, X, X, 2, 7, 5, 3, 4, 6, 1, 8, 9, X, X, X, X, X, X,
+        ],
+        [
+            1, 7, 8, 9, 3, 6, 5, 2, 4, 1, 7, 8, 9, 3, 6, 2, 8, 7, 4, 5, 1,
+        ],
+        [
+            2, 4, 3, 5, 8, 1, 9, 6, 7, 4, 3, 5, 8, 1, 2, 9, 4, 5, 3, 7, 6,
+        ],
+        [
+            6, 5, 9, 4, 2, 7, 8, 3, 1, 6, 2, 9, 5, 4, 7, 1, 6, 3, 8, 2, 9,
+        ],
+        [
+            8, 9, 2, 1, 4, 3, 6, 7, 5, X, X, X, 6, 7, 8, 5, 3, 1, 2, 9, 4,
+        ],
+        [
+            4, 6, 5, 7, 9, 2, 1, 8, 3, X, X, X, 1, 5, 3, 4, 9, 2, 6, 8, 7,
+        ],
+        [
+            3, 1, 7, 6, 5, 8, 4, 9, 2, X, X, X, 4, 2, 9, 8, 7, 6, 5, 1, 3,
+        ],
+        [
+            5, 8, 1, 2, 7, 9, 3, 4, 6, X, X, X, 7, 6, 1, 3, 2, 8, 9, 4, 5,
+        ],
+        [
+            9, 2, 4, 3, 6, 5, 7, 1, 8, X, X, X, 2, 9, 5, 6, 1, 4, 7, 3, 8,
+        ],
+        [
+            7, 3, 6, 8, 1, 4, 2, 5, 9, X, X, X, 3, 8, 4, 7, 5, 9, 1, 6, 2,
+        ],
+    ];
 
     let (mut sys, vars) = make_samurai_sudoku(&puzzle);
     let dict = sys.solve_any().expect("solution");
diff --git a/tests/sendmoremoney.rs b/tests/sendmoremoney.rs
index b7b02b7..b5eeddb 100644
--- a/tests/sendmoremoney.rs
+++ b/tests/sendmoremoney.rs
@@ -4,11 +4,11 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{Puzzle,Solution,VarToken};
+use puzzle_solver::{Puzzle, Solution, VarToken};
 
 fn make_send_more_money() -> (Puzzle, Vec<VarToken>) {
     let mut sys = Puzzle::new();
-    let vars = sys.new_vars_with_candidates_1d(8, &[0,1,2,3,4,5,6,7,8,9]);
+    let vars = sys.new_vars_with_candidates_1d(8, &[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
     let (s, e, n, d) = (vars[0], vars[1], vars[2], vars[3]);
     let (m, o, r, y) = (vars[4], vars[5], vars[6], vars[7]);
 
@@ -32,7 +32,10 @@ fn print_send_more_money(dict: &Solution, vars: &Vec<VarToken>) {
     println!("   {} {} {} {}", dict[s], dict[e], dict[n], dict[d]);
     println!(" + {} {} {} {}", dict[m], dict[o], dict[r], dict[e]);
     println!("----------");
-    println!(" {} {} {} {} {}", dict[m], dict[o], dict[n], dict[e], dict[y]);
+    println!(
+        " {} {} {} {} {}",
+        dict[m], dict[o], dict[n], dict[e], dict[y]
+    );
 }
 
 fn verify_send_more_money(dict: &Solution, vars: &Vec<VarToken>) {
@@ -51,7 +54,7 @@ fn verify_send_more_money(dict: &Solution, vars: &Vec<VarToken>) {
 
 #[test]
 fn sendmoremoney_carry() {
-    let carry = [0,1];
+    let carry = [0, 1];
 
     let (mut sys, vars) = make_send_more_money();
     let (s, e, n, d) = (vars[0], vars[1], vars[2], vars[3]);
@@ -61,10 +64,10 @@ fn sendmoremoney_carry() {
     let c3 = sys.new_var_with_candidates(&carry);
     sys.intersect_candidates(m, &carry); // c4 == m.
 
-    sys.equals(     d + e, 10 * c1 + y);
+    sys.equals(d + e, 10 * c1 + y);
     sys.equals(c1 + n + r, 10 * c2 + e);
     sys.equals(c2 + e + o, 10 * c3 + n);
-    sys.equals(c3 + s + m, 10 *  m + o);
+    sys.equals(c3 + s + m, 10 * m + o);
 
     let dict = sys.solve_unique().expect("solution");
     print_send_more_money(&dict, &vars);
diff --git a/tests/sudoku.rs b/tests/sudoku.rs
index b2b59d7..01986d6 100644
--- a/tests/sudoku.rs
+++ b/tests/sudoku.rs
@@ -4,7 +4,7 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{Puzzle, Solution, Val, VarToken};
 
 const SQRT_SIZE: usize = 3;
 const SIZE: usize = 9;
@@ -12,7 +12,7 @@ type Board = [[Val; SIZE]; SIZE];
 
 fn make_sudoku(board: &Board) -> (Puzzle, Vec<Vec<VarToken>>) {
     let mut sys = Puzzle::new();
-    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1,2,3,4,5,6,7,8,9]);
+    let vars = sys.new_vars_with_candidates_2d(SIZE, SIZE, &[1, 2, 3, 4, 5, 6, 7, 8, 9]);
 
     for y in 0..SIZE {
         sys.all_different(&vars[y]);
@@ -25,8 +25,7 @@ fn make_sudoku(board: &Board) -> (Puzzle, Vec<Vec<VarToken>>) {
     for block in 0..SIZE {
         let x0 = SQRT_SIZE * (block % SQRT_SIZE);
         let y0 = SQRT_SIZE * (block / SQRT_SIZE);
-        sys.all_different((0..SIZE).map(|n|
-                &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
+        sys.all_different((0..SIZE).map(|n| &vars[y0 + (n / SQRT_SIZE)][x0 + (n % SQRT_SIZE)]));
     }
 
     for y in 0..SIZE {
@@ -48,9 +47,11 @@ fn print_sudoku(dict: &Solution, vars: &Vec<Vec<VarToken>>) {
         }
 
         for x in 0..SIZE {
-            print!("{}{}",
-                   if x % SQRT_SIZE == 0 { " " } else { "" },
-                   dict[vars[y][x]]);
+            print!(
+                "{}{}",
+                if x % SQRT_SIZE == 0 { " " } else { "" },
+                dict[vars[y][x]]
+            );
         }
         println!();
     }
@@ -67,30 +68,28 @@ fn verify_sudoku(dict: &Solution, vars: &Vec<Vec<VarToken>>, expected: &Board) {
 #[test]
 fn sudoku_hardest() {
     let puzzle = [
-        [ 8,0,0,  0,0,0,  0,0,0 ],
-        [ 0,0,3,  6,0,0,  0,0,0 ],
-        [ 0,7,0,  0,9,0,  2,0,0 ],
-
-        [ 0,5,0,  0,0,7,  0,0,0 ],
-        [ 0,0,0,  0,4,5,  7,0,0 ],
-        [ 0,0,0,  1,0,0,  0,3,0 ],
-
-        [ 0,0,1,  0,0,0,  0,6,8 ],
-        [ 0,0,8,  5,0,0,  0,1,0 ],
-        [ 0,9,0,  0,0,0,  4,0,0 ] ];
+        [8, 0, 0, 0, 0, 0, 0, 0, 0],
+        [0, 0, 3, 6, 0, 0, 0, 0, 0],
+        [0, 7, 0, 0, 9, 0, 2, 0, 0],
+        [0, 5, 0, 0, 0, 7, 0, 0, 0],
+        [0, 0, 0, 0, 4, 5, 7, 0, 0],
+        [0, 0, 0, 1, 0, 0, 0, 3, 0],
+        [0, 0, 1, 0, 0, 0, 0, 6, 8],
+        [0, 0, 8, 5, 0, 0, 0, 1, 0],
+        [0, 9, 0, 0, 0, 0, 4, 0, 0],
+    ];
 
     let expected = [
-        [ 8,1,2,  7,5,3,  6,4,9 ],
-        [ 9,4,3,  6,8,2,  1,7,5 ],
-        [ 6,7,5,  4,9,1,  2,8,3 ],
-
-        [ 1,5,4,  2,3,7,  8,9,6 ],
-        [ 3,6,9,  8,4,5,  7,2,1 ],
-        [ 2,8,7,  1,6,9,  5,3,4 ],
-
-        [ 5,2,1,  9,7,4,  3,6,8 ],
-        [ 4,3,8,  5,2,6,  9,1,7 ],
-        [ 7,9,6,  3,1,8,  4,5,2 ] ];
+        [8, 1, 2, 7, 5, 3, 6, 4, 9],
+        [9, 4, 3, 6, 8, 2, 1, 7, 5],
+        [6, 7, 5, 4, 9, 1, 2, 8, 3],
+        [1, 5, 4, 2, 3, 7, 8, 9, 6],
+        [3, 6, 9, 8, 4, 5, 7, 2, 1],
+        [2, 8, 7, 1, 6, 9, 5, 3, 4],
+        [5, 2, 1, 9, 7, 4, 3, 6, 8],
+        [4, 3, 8, 5, 2, 6, 9, 1, 7],
+        [7, 9, 6, 3, 1, 8, 4, 5, 2],
+    ];
 
     let (mut sys, vars) = make_sudoku(&puzzle);
     let solution = sys.solve_any().expect("solution");
@@ -102,30 +101,28 @@ fn sudoku_hardest() {
 #[test]
 fn sudoku_wikipedia() {
     let puzzle = [
-        [ 5,3,0,  0,7,0,  0,0,0 ],
-        [ 6,0,0,  1,9,5,  0,0,0 ],
-        [ 0,9,8,  0,0,0,  0,6,0 ],
-
-        [ 8,0,0,  0,6,0,  0,0,3 ],
-        [ 4,0,0,  8,0,3,  0,0,1 ],
-        [ 7,0,0,  0,2,0,  0,0,6 ],
-
-        [ 0,6,0,  0,0,0,  2,8,0 ],
-        [ 0,0,0,  4,1,9,  0,0,5 ],
-        [ 0,0,0,  0,8,0,  0,7,9 ] ];
+        [5, 3, 0, 0, 7, 0, 0, 0, 0],
+        [6, 0, 0, 1, 9, 5, 0, 0, 0],
+        [0, 9, 8, 0, 0, 0, 0, 6, 0],
+        [8, 0, 0, 0, 6, 0, 0, 0, 3],
+        [4, 0, 0, 8, 0, 3, 0, 0, 1],
+        [7, 0, 0, 0, 2, 0, 0, 0, 6],
+        [0, 6, 0, 0, 0, 0, 2, 8, 0],
+        [0, 0, 0, 4, 1, 9, 0, 0, 5],
+        [0, 0, 0, 0, 8, 0, 0, 7, 9],
+    ];
 
     let expected = [
-        [ 5,3,4,  6,7,8,  9,1,2 ],
-        [ 6,7,2,  1,9,5,  3,4,8 ],
-        [ 1,9,8,  3,4,2,  5,6,7 ],
-
-        [ 8,5,9,  7,6,1,  4,2,3 ],
-        [ 4,2,6,  8,5,3,  7,9,1 ],
-        [ 7,1,3,  9,2,4,  8,5,6 ],
-
-        [ 9,6,1,  5,3,7,  2,8,4 ],
-        [ 2,8,7,  4,1,9,  6,3,5 ],
-        [ 3,4,5,  2,8,6,  1,7,9 ] ];
+        [5, 3, 4, 6, 7, 8, 9, 1, 2],
+        [6, 7, 2, 1, 9, 5, 3, 4, 8],
+        [1, 9, 8, 3, 4, 2, 5, 6, 7],
+        [8, 5, 9, 7, 6, 1, 4, 2, 3],
+        [4, 2, 6, 8, 5, 3, 7, 9, 1],
+        [7, 1, 3, 9, 2, 4, 8, 5, 6],
+        [9, 6, 1, 5, 3, 7, 2, 8, 4],
+        [2, 8, 7, 4, 1, 9, 6, 3, 5],
+        [3, 4, 5, 2, 8, 6, 1, 7, 9],
+    ];
 
     let (mut sys, vars) = make_sudoku(&puzzle);
     let solution = sys.solve_any().expect("solution");
diff --git a/tests/sujiko.rs b/tests/sujiko.rs
index 657cc86..a00e6be 100644
--- a/tests/sujiko.rs
+++ b/tests/sujiko.rs
@@ -5,15 +5,14 @@
 
 extern crate puzzle_solver;
 
-use puzzle_solver::{Puzzle,Solution,Val,VarToken};
+use puzzle_solver::{Puzzle, Solution, Val, VarToken};
 
 const SIZE: usize = 3;
 type Board = [[Val; SIZE]; SIZE];
 
-fn make_sujiko(board: &Board, tl: Val, tr: Val, bl: Val, br: Val)
-        -> (Puzzle, Vec<Vec<VarToken>>) {
+fn make_sujiko(board: &Board, tl: Val, tr: Val, bl: Val, br: Val) -> (Puzzle, Vec<Vec<VarToken>>) {
     let mut sys = Puzzle::new();
-    let vars = sys.new_vars_with_candidates_2d(3, 3, &[1,2,3,4,5,6,7,8,9]);
+    let vars = sys.new_vars_with_candidates_2d(3, 3, &[1, 2, 3, 4, 5, 6, 7, 8, 9]);
 
     sys.all_different(vars.iter().flat_map(|it| it));
 
@@ -22,8 +21,10 @@ fn make_sujiko(board: &Board, tl: Val, tr: Val, bl: Val, br: Val)
     sys.equals(bl, vars[1][0] + vars[1][1] + vars[2][0] + vars[2][1]);
     sys.equals(br, vars[1][1] + vars[1][2] + vars[2][1] + vars[2][2]);
 
-    sys.equals(tl + tr + bl + br - (1..(9 + 1)).sum::<Val>(),
-            vars[0][1] + vars[1][0] + 3 * vars[1][1] + vars[1][2] + vars[2][1]);
+    sys.equals(
+        tl + tr + bl + br - (1..(9 + 1)).sum::<Val>(),
+        vars[0][1] + vars[1][0] + 3 * vars[1][1] + vars[1][2] + vars[2][1],
+    );
 
     for y in 0..SIZE {
         for x in 0..SIZE {
@@ -56,8 +57,8 @@ fn verify_sujiko(dict: &Solution, vars: &Vec<Vec<VarToken>>, expected: &Board) {
 
 #[test]
 fn sujiko_simetric() {
-    let puzzle   = [ [ 6,0,9 ], [ 0,0,0 ], [ 5,0,0 ] ];
-    let expected = [ [ 6,2,9 ], [ 8,1,3 ], [ 5,4,7 ] ];
+    let puzzle = [[6, 0, 9], [0, 0, 0], [5, 0, 0]];
+    let expected = [[6, 2, 9], [8, 1, 3], [5, 4, 7]];
 
     let (mut sys, vars) = make_sujiko(&puzzle, 17, 15, 18, 15);
     let dict = sys.solve_unique().expect("solution");
diff --git a/tests/takuzu.rs b/tests/takuzu.rs
index 8359bbb..97c6f68 100644
--- a/tests/takuzu.rs
+++ b/tests/takuzu.rs
@@ -4,9 +4,9 @@
 
 extern crate puzzle_solver;
 
+use puzzle_solver::*;
 use std::iter;
 use std::rc::Rc;
-use puzzle_solver::*;
 
 const X: Val = -1;
 
@@ -19,12 +19,11 @@ struct BinaryRepr {
 }
 
 impl Constraint for BinaryRepr {
-    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item=&'a VarToken> + 'a> {
+    fn vars<'a>(&'a self) -> Box<dyn Iterator<Item = &'a VarToken> + 'a> {
         Box::new(iter::once(&self.value).chain(&self.bits))
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val)
-            -> PsResult<()> {
+    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
         if var == self.value {
             let mut val = val;
             for &var in self.bits.iter() {
@@ -33,7 +32,8 @@ impl Constraint for BinaryRepr {
             }
         } else if let Some(bitpos) = self.bits.iter().position(|&v| v == var) {
             let bit = 1 << bitpos;
-            let discard = search.get_unassigned(self.value)
+            let discard = search
+                .get_unassigned(self.value)
                 .filter(|c| c & bit != val * bit)
                 .collect::<Vec<_>>();
 
@@ -45,8 +45,7 @@ impl Constraint for BinaryRepr {
         Ok(())
     }
 
-    fn substitute(&self, _from: VarToken, _to: VarToken)
-            -> PsResult<Rc<dyn Constraint>> {
+    fn substitute(&self, _from: VarToken, _to: VarToken) -> PsResult<Rc<dyn Constraint>> {
         unimplemented!();
     }
 }
@@ -83,13 +82,16 @@ fn make_takuzu(puzzle: &Vec<Vec<Val>>) -> (Puzzle, Vec<Vec<VarToken>>) {
     let col_candidates = make_sums(width);
 
     let mut sys = Puzzle::new();
-    let vars = sys.new_vars_with_candidates_2d(width, height, &[0,1]);
+    let vars = sys.new_vars_with_candidates_2d(width, height, &[0, 1]);
     let row_values = sys.new_vars_with_candidates_1d(height, &row_candidates);
     let col_values = sys.new_vars_with_candidates_1d(width, &col_candidates);
 
     for y in 0..height {
         let total = (height as Val) / 2;
-        sys.equals(total, vars[y].iter().fold(LinExpr::from(0), |sum, &x| sum + x));
+        sys.equals(
+            total,
+            vars[y].iter().fold(LinExpr::from(0), |sum, &x| sum + x),
+        );
         sys.add_constraint(BinaryRepr {
             value: row_values[y],
             bits: vars[y].clone(),
@@ -98,7 +100,10 @@ fn make_takuzu(puzzle: &Vec<Vec<Val>>) -> (Puzzle, Vec<Vec<VarToken>>) {
 
     for x in 0..width {
         let total = (width as Val) / 2;
-        sys.equals(total, vars.iter().fold(LinExpr::from(0), |sum, row| sum + row[x]));
+        sys.equals(
+            total,
+            vars.iter().fold(LinExpr::from(0), |sum, row| sum + row[x]),
+        );
         sys.add_constraint(BinaryRepr {
             value: col_values[x],
             bits: (0..height).map(|y| vars[y][x]).collect(),
@@ -108,15 +113,18 @@ fn make_takuzu(puzzle: &Vec<Vec<Val>>) -> (Puzzle, Vec<Vec<VarToken>>) {
     // No three in a row, i.e. not: 000, 111.
     for y in 0..height {
         for window in vars[y].windows(3) {
-            let disjunction = sys.new_var_with_candidates(&[1,2]);
+            let disjunction = sys.new_var_with_candidates(&[1, 2]);
             sys.equals(window[0] + window[1] + window[2], disjunction);
         }
     }
 
     for x in 0..width {
         for y in 0..(height - 2) {
-            let disjunction = sys.new_var_with_candidates(&[1,2]);
-            sys.equals(vars[y + 0][x] + vars[y + 1][x] + vars[y + 2][x], disjunction);
+            let disjunction = sys.new_var_with_candidates(&[1, 2]);
+            sys.equals(
+                vars[y + 0][x] + vars[y + 1][x] + vars[y + 2][x],
+                disjunction,
+            );
         }
     }
 
@@ -154,12 +162,13 @@ fn verify_takuzu(dict: &Solution, vars: &Vec<Vec<VarToken>>, expected: &[Val]) {
 #[test]
 fn takuzu_grid1() {
     let puzzle = vec![
-        vec![ X,1,0,X,X,X ],
-        vec![ 1,X,X,X,0,X ],
-        vec![ X,X,0,X,X,X ],
-        vec![ 1,1,X,X,1,0 ],
-        vec![ X,X,X,X,0,X ],
-        vec![ X,X,X,X,X,X ] ];
+        vec![X, 1, 0, X, X, X],
+        vec![1, X, X, X, 0, X],
+        vec![X, X, 0, X, X, X],
+        vec![1, 1, X, X, 1, 0],
+        vec![X, X, X, X, 0, X],
+        vec![X, X, X, X, X, X],
+    ];
 
     let (mut sys, vars) = make_takuzu(&puzzle);
     let solutions = sys.solve_all();
@@ -172,18 +181,19 @@ fn takuzu_grid1() {
 #[test]
 fn takuzu_grid2() {
     let puzzle = vec![
-        vec![ 0,X,X,X,X,1,1,X,X,0,X,X ],
-        vec![ X,X,X,1,X,X,X,0,X,X,X,X ],
-        vec![ X,0,X,X,X,X,1,X,X,X,0,0 ],
-        vec![ 1,X,X,1,X,X,1,1,X,X,X,1 ],
-        vec![ X,X,X,X,X,X,X,X,X,1,X,X ],
-        vec![ 0,X,0,X,X,X,1,X,X,X,X,X ],
-        vec![ X,X,X,X,0,X,X,X,X,X,X,X ],
-        vec![ X,X,X,X,0,1,X,0,X,X,X,X ],
-        vec![ X,X,0,0,X,X,0,X,0,X,X,0 ],
-        vec![ X,X,X,X,X,1,X,X,X,X,1,X ],
-        vec![ 1,0,X,0,X,X,X,X,X,X,X,X ],
-        vec![ X,X,1,X,X,X,X,1,X,X,0,0 ] ];
+        vec![0, X, X, X, X, 1, 1, X, X, 0, X, X],
+        vec![X, X, X, 1, X, X, X, 0, X, X, X, X],
+        vec![X, 0, X, X, X, X, 1, X, X, X, 0, 0],
+        vec![1, X, X, 1, X, X, 1, 1, X, X, X, 1],
+        vec![X, X, X, X, X, X, X, X, X, 1, X, X],
+        vec![0, X, 0, X, X, X, 1, X, X, X, X, X],
+        vec![X, X, X, X, 0, X, X, X, X, X, X, X],
+        vec![X, X, X, X, 0, 1, X, 0, X, X, X, X],
+        vec![X, X, 0, 0, X, X, 0, X, 0, X, X, 0],
+        vec![X, X, X, X, X, 1, X, X, X, X, 1, X],
+        vec![1, 0, X, 0, X, X, X, X, X, X, X, X],
+        vec![X, X, 1, X, X, X, X, 1, X, X, 0, 0],
+    ];
 
     let expected = [
         0b_010101101001,
@@ -197,7 +207,8 @@ fn takuzu_grid2() {
         0b_110010010110,
         0b_010101101010,
         0b_101010010101,
-        0b_101011010100 ];
+        0b_101011010100,
+    ];
 
     let (mut sys, vars) = make_takuzu(&puzzle);
     let dict = sys.solve_unique().expect("solution");
@@ -209,18 +220,19 @@ fn takuzu_grid2() {
 #[test]
 fn takuzu_grid3() {
     let puzzle = vec![
-        vec![ X,X,X,0,X,0,X,X,X,X,0,X ],
-        vec![ 1,X,X,X,X,X,X,1,X,X,X,1 ],
-        vec![ X,X,1,1,X,X,X,X,X,X,0,X ],
-        vec![ X,0,X,X,X,X,X,X,X,X,X,0 ],
-        vec![ X,X,X,0,X,X,1,1,0,X,X,X ],
-        vec![ 0,X,0,0,X,0,X,1,X,X,0,X ],
-        vec![ X,X,X,X,X,X,0,X,X,X,0,X ],
-        vec![ 1,X,1,X,0,X,X,X,X,X,X,X ],
-        vec![ X,X,X,X,X,X,1,0,1,X,0,X ],
-        vec![ X,1,X,X,0,X,X,X,X,0,0,X ],
-        vec![ X,X,X,1,X,X,X,0,X,X,X,X ],
-        vec![ X,X,X,X,X,1,1,X,X,1,X,X ] ];
+        vec![X, X, X, 0, X, 0, X, X, X, X, 0, X],
+        vec![1, X, X, X, X, X, X, 1, X, X, X, 1],
+        vec![X, X, 1, 1, X, X, X, X, X, X, 0, X],
+        vec![X, 0, X, X, X, X, X, X, X, X, X, 0],
+        vec![X, X, X, 0, X, X, 1, 1, 0, X, X, X],
+        vec![0, X, 0, 0, X, 0, X, 1, X, X, 0, X],
+        vec![X, X, X, X, X, X, 0, X, X, X, 0, X],
+        vec![1, X, 1, X, 0, X, X, X, X, X, X, X],
+        vec![X, X, X, X, X, X, 1, 0, 1, X, 0, X],
+        vec![X, 1, X, X, 0, X, X, X, X, 0, 0, X],
+        vec![X, X, X, 1, X, X, X, 0, X, X, X, X],
+        vec![X, X, X, X, X, 1, 1, X, X, 1, X, X],
+    ];
 
     let expected = [
         0b_101010011001,
@@ -234,7 +246,8 @@ fn takuzu_grid3() {
         0b_010010101101,
         0b_011001011001,
         0b_100110100110,
-        0b_010101100110 ];
+        0b_010101100110,
+    ];
 
     let (mut sys, vars) = make_takuzu(&puzzle);
     let dict = sys.solve_unique().expect("solution");
@@ -246,18 +259,19 @@ fn takuzu_grid3() {
 #[test]
 fn takuzu_grid4() {
     let puzzle = vec![
-        vec![ X,X,X,X,X,1,1,X,X,0,X,X ],
-        vec![ X,X,X,1,X,X,X,0,X,X,X,X ],
-        vec![ X,0,X,X,X,X,1,X,X,X,0,0 ],
-        vec![ X,X,X,1,X,X,1,1,X,X,X,1 ],
-        vec![ X,X,X,X,X,X,X,X,X,1,X,X ],
-        vec![ X,X,0,X,X,X,1,X,X,X,X,X ],
-        vec![ X,X,X,X,0,X,X,X,X,X,X,X ],
-        vec![ X,X,X,X,0,1,X,0,X,X,X,X ],
-        vec![ X,X,0,0,X,X,0,X,0,X,X,0 ],
-        vec![ X,X,X,X,X,1,X,X,X,X,1,X ],
-        vec![ X,X,X,0,X,X,X,X,X,X,X,X ],
-        vec![ X,X,1,X,X,X,X,1,X,X,0,0 ] ];
+        vec![X, X, X, X, X, 1, 1, X, X, 0, X, X],
+        vec![X, X, X, 1, X, X, X, 0, X, X, X, X],
+        vec![X, 0, X, X, X, X, 1, X, X, X, 0, 0],
+        vec![X, X, X, 1, X, X, 1, 1, X, X, X, 1],
+        vec![X, X, X, X, X, X, X, X, X, 1, X, X],
+        vec![X, X, 0, X, X, X, 1, X, X, X, X, X],
+        vec![X, X, X, X, 0, X, X, X, X, X, X, X],
+        vec![X, X, X, X, 0, 1, X, 0, X, X, X, X],
+        vec![X, X, 0, 0, X, X, 0, X, 0, X, X, 0],
+        vec![X, X, X, X, X, 1, X, X, X, X, 1, X],
+        vec![X, X, X, 0, X, X, X, X, X, X, X, X],
+        vec![X, X, 1, X, X, X, X, 1, X, X, 0, 0],
+    ];
 
     let (mut sys, vars) = make_takuzu(&puzzle);
     let dict = &sys.solve_any().expect("solution");
diff --git a/tests/xkcd.rs b/tests/xkcd.rs
index e4bb547..851a0e1 100644
--- a/tests/xkcd.rs
+++ b/tests/xkcd.rs
@@ -9,7 +9,7 @@ extern crate puzzle_solver;
 
 use num_rational::Ratio;
 use num_traits::ToPrimitive;
-use puzzle_solver::{LinExpr,Puzzle,Val};
+use puzzle_solver::{LinExpr, Puzzle, Val};
 
 #[test]
 fn xkcd_knapsack() {
@@ -32,8 +32,12 @@ fn xkcd_knapsack() {
         vars.push(var)
     }
 
-    sys.equals(total, vars.iter().zip(menu.iter()).fold(LinExpr::from(0),
-            |sum, (&var, &(cost, _))| sum + var * cost));
+    sys.equals(
+        total,
+        vars.iter()
+            .zip(menu.iter())
+            .fold(LinExpr::from(0), |sum, (&var, &(cost, _))| sum + var * cost),
+    );
 
     let solutions = sys.solve_all();
     assert_eq!(solutions.len(), 2);
diff --git a/tests/zebra.rs b/tests/zebra.rs
index 6eaf41a..300cb84 100644
--- a/tests/zebra.rs
+++ b/tests/zebra.rs
@@ -9,32 +9,66 @@ extern crate puzzle_solver;
 
 use puzzle_solver::Puzzle;
 
-#[derive(Clone,Copy,Debug)]
-enum Nat { Dane, Englishman, German, Norwegian, Swede }
+#[derive(Clone, Copy, Debug)]
+enum Nat {
+    Dane,
+    Englishman,
+    German,
+    Norwegian,
+    Swede,
+}
 
-#[derive(Clone,Copy,Debug)]
-enum Col { Blue, Green, Red, White, Yellow }
+#[derive(Clone, Copy, Debug)]
+enum Col {
+    Blue,
+    Green,
+    Red,
+    White,
+    Yellow,
+}
 
-#[derive(Clone,Copy,Debug)]
-enum Dri { Beer, Coffee, Milk, Tea, Water }
+#[derive(Clone, Copy, Debug)]
+enum Dri {
+    Beer,
+    Coffee,
+    Milk,
+    Tea,
+    Water,
+}
 
-#[derive(Clone,Copy,Debug)]
-enum Smo { Blend, BlueMaster, Dunhill, PallMall, Prince }
+#[derive(Clone, Copy, Debug)]
+enum Smo {
+    Blend,
+    BlueMaster,
+    Dunhill,
+    PallMall,
+    Prince,
+}
 
-#[derive(Clone,Copy,Debug)]
-enum Pet { Bird, Cat, Dog, Fish, Horse }
+#[derive(Clone, Copy, Debug)]
+enum Pet {
+    Bird,
+    Cat,
+    Dog,
+    Fish,
+    Horse,
+}
 
 #[test]
 fn zebra() {
-    use crate::Nat::*; use crate::Col::*; use crate::Dri::*; use crate::Smo::*; use crate::Pet::*;
+    use crate::Col::*;
+    use crate::Dri::*;
+    use crate::Nat::*;
+    use crate::Pet::*;
+    use crate::Smo::*;
 
     // #1: There are five houses.
     let mut sys = Puzzle::new();
-    let nat_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
-    let col_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
-    let dri_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
-    let smo_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
-    let pet_var = sys.new_vars_with_candidates_1d(5, &[1,2,3,4,5]);
+    let nat_var = sys.new_vars_with_candidates_1d(5, &[1, 2, 3, 4, 5]);
+    let col_var = sys.new_vars_with_candidates_1d(5, &[1, 2, 3, 4, 5]);
+    let dri_var = sys.new_vars_with_candidates_1d(5, &[1, 2, 3, 4, 5]);
+    let smo_var = sys.new_vars_with_candidates_1d(5, &[1, 2, 3, 4, 5]);
+    let pet_var = sys.new_vars_with_candidates_1d(5, &[1, 2, 3, 4, 5]);
 
     let nat = |n| nat_var[n as usize];
     let col = |n| col_var[n as usize];
@@ -76,11 +110,11 @@ fn zebra() {
     sys.equals(nat(Norwegian), 1);
 
     // #11: The man who smokes Blend lives in the house next to the house with cats.
-    let neighbour11 = sys.new_var_with_candidates(&[-1,1]);
+    let neighbour11 = sys.new_var_with_candidates(&[-1, 1]);
     sys.equals(smo(Blend), pet(Cat) + neighbour11);
 
     // #12: In a house next to the house where they have a horse, they smoke Dunhill.
-    let neighbour12 = sys.new_var_with_candidates(&[-1,1]);
+    let neighbour12 = sys.new_var_with_candidates(&[-1, 1]);
     sys.equals(pet(Horse), smo(Dunhill) + neighbour12);
 
     // #13: The man who smokes Blue Master drinks beer.
@@ -90,23 +124,24 @@ fn zebra() {
     sys.equals(nat(German), smo(Prince));
 
     // #15: The Norwegian lives next to the blue house.
-    let neighbour15 = sys.new_var_with_candidates(&[-1,1]);
+    let neighbour15 = sys.new_var_with_candidates(&[-1, 1]);
     sys.equals(nat(Norwegian), col(Blue) + neighbour15);
 
     // #16: They drink water in a house next to the house where they smoke Blend.
-    let neighbour16 = sys.new_var_with_candidates(&[-1,1]);
+    let neighbour16 = sys.new_var_with_candidates(&[-1, 1]);
     sys.equals(dri(Water), smo(Blend) + neighbour16);
 
     let dict = sys.solve_any().expect("solution");
 
     let expected = [
-        (Norwegian,  Yellow, Water,  Dunhill,    Cat),
-        (Dane,       Blue,   Tea,    Blend,      Horse),
-        (Englishman, Red,    Milk,   PallMall,   Bird),
-        (German,     Green,  Coffee, Prince,     Fish),
-        (Swede,      White,  Beer,   BlueMaster, Dog) ];
+        (Norwegian, Yellow, Water, Dunhill, Cat),
+        (Dane, Blue, Tea, Blend, Horse),
+        (Englishman, Red, Milk, PallMall, Bird),
+        (German, Green, Coffee, Prince, Fish),
+        (Swede, White, Beer, BlueMaster, Dog),
+    ];
 
-    for &(n,c,d,s,p) in expected.iter() {
+    for &(n, c, d, s, p) in expected.iter() {
         assert_eq!(dict[nat(n)], dict[col(c)]);
         assert_eq!(dict[nat(n)], dict[dri(d)]);
         assert_eq!(dict[nat(n)], dict[smo(s)]);