diff --git a/.gitignore b/.gitignore
index ba2a97b..26846b6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 node_modules
 coverage
+npm-debug.log
\ No newline at end of file
diff --git a/package.json b/package.json
index 3a2cda5..8323107 100644
--- a/package.json
+++ b/package.json
@@ -9,15 +9,12 @@
   "author": "Marcus Stade",
   "license": "MIT",
   "devDependencies": {
+    "coveralls": "~2.8.0",
+    "expect.js": "^0.3.1",
     "istanbul": "~0.2.4",
     "mocha": "~1.17.1",
-    "chai": "~1.9.0",
-    "coveralls": "~2.8.0",
     "mocha-lcov-reporter": "0.0.1",
-    "sinon": "~1.9.0",
-    "mocha-sinon": "~1.1.0",
-    "sinon-chai": "~2.5.0",
-    "expect.js": "^0.3.1"
+    "must": "git://github.com/mstade/js-must#throw-error-instance"
   },
   "repository": {
     "type": "git",
diff --git a/test/apply.js b/test/apply.js
index 0ba6228..817587d 100644
--- a/test/apply.js
+++ b/test/apply.js
@@ -23,7 +23,7 @@ describe('apply', function() {
   describe('when given a function `fn`', function() {
     describe('and no arguments', function(done) {
       it('should call the function without arguments', function(done) {      
-	var fn = function() {
+        var fn = function() {
           expect(arguments.length).to.equal(0)
           done()
         }
@@ -32,14 +32,14 @@ describe('apply', function() {
       })
 
       it('should proxy the functions return value', function() {
-	expect(apply(constantly(3))).to.equal(3)
+        expect(apply(constantly(3))).to.equal(3)
       })
 
       describe('and `fn` is bound', function() {
         it('should not affect the binding', function(done) {
-	  var owner = {}
+          var owner = {}
 
-	  var fn = function() {
+          var fn = function() {
             expect(arguments.length).to.equal(0)
             expect(this).to.equal(owner)
             done()
@@ -52,7 +52,7 @@ describe('apply', function() {
 
     describe('and when given arguments', function(done) {
       it('should call the function with arguments', function(done) {
-	var fn = function() {
+        var fn = function() {
           expect(slice(arguments)).to.eql([1, true, 'wibble'])
           done()
         }
@@ -61,14 +61,14 @@ describe('apply', function() {
       })
 
       it('should proxy the functions return value', function() {
-	expect(apply(constantly, [3])).to.be.a('function')
+        expect(apply(constantly, [3])).to.be.a(Function)
       })
 
       describe('and `fn` is bound', function() {
         it('should not affect the binding', function(done) {
-	  var owner = {}
+          var owner = {}
 
-	  var fn = function() {
+          var fn = function() {
             expect(slice(arguments)).to.eql([1, true, 'wibble'])
             expect(this).to.equal(owner)
             done()
@@ -82,7 +82,7 @@ describe('apply', function() {
 })
 
 var constantly = require('../lib/constantly')
-  , expect     = require('chai').expect
+  , expect     = require('must')
   , slice      = require('../lib/slice')
   , apply      = require('../lib/apply')
   , each       = require('../lib/each')
diff --git a/test/assert.js b/test/assert.js
index 0ebdab4..cd32cb1 100644
--- a/test/assert.js
+++ b/test/assert.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , assert = require('../lib/assert')
   , each   = require('../lib/each')
   , src    = require('../lib/src')
@@ -24,7 +24,7 @@ describe('assert', function() {
         })
 
         describe('and also given an instance of Error', function() {
-          it('should throw that error', function() {
+          it('should throw that instance', function() {
             var err = new Error('sad face')
             expect($(assert, x, err)).to.throw(err)
           })
diff --git a/test/call.js b/test/call.js
index d79f945..796f267 100644
--- a/test/call.js
+++ b/test/call.js
@@ -73,7 +73,7 @@ describe('call', function() {
   })
 })
 
-var expect = require('chai').expect
+var expect = require('must')
   , slice  = require('../lib/slice')
   , each   = require('../lib/each')
   , call   = require('../lib/call')
\ No newline at end of file
diff --git a/test/compose.js b/test/compose.js
index 82c2a0a..8d22592 100644
--- a/test/compose.js
+++ b/test/compose.js
@@ -1,5 +1,5 @@
 var partial = require('../lib/partial')
-  , expect  = require('chai').expect
+  , expect  = require('must')
   , comp    = require('../lib/compose')
 
 describe('compose', function() {
diff --git a/test/constantly.js b/test/constantly.js
index d1b391a..9887b99 100644
--- a/test/constantly.js
+++ b/test/constantly.js
@@ -1,5 +1,5 @@
 var constantly = require('../lib/constantly')
-  , expect     = require('chai').expect
+  , expect     = require('must')
   , each       = require('../lib/each')
   , src        = require('../lib/src')
 
diff --git a/test/count.js b/test/count.js
index 444d881..5eb81fc 100644
--- a/test/count.js
+++ b/test/count.js
@@ -1,5 +1,5 @@
 var partial = require('../lib/partial')
-  , expect  = require('chai').expect
+  , expect  = require('must')
   , count   = require('../lib/count')
   , seq     = require('../lib/seq')
 
diff --git a/test/each.js b/test/each.js
index 7276314..e739982 100644
--- a/test/each.js
+++ b/test/each.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , each   = require('../lib/each')
   , src    = require('../lib/src')
   , seq    = require('../lib/seq')
diff --git a/test/eq.js b/test/eq.js
index cd9d04e..2e47879 100644
--- a/test/eq.js
+++ b/test/eq.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , each   = require('../lib/each')
   , eq     = require('../lib/eq')
 
diff --git a/test/get.js b/test/get.js
index ca9774e..585e4f8 100644
--- a/test/get.js
+++ b/test/get.js
@@ -1,5 +1,5 @@
 const partial = require('../lib/partial')
-    , expect  = require('chai').expect
+    , expect  = require('must')
     , each    = require('../lib/each')
     , get     = require('../lib/get')
 
diff --git a/test/gt.js b/test/gt.js
index ca429e3..0b23c8f 100644
--- a/test/gt.js
+++ b/test/gt.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , gt     = require('../lib/gt')
 
 describe('gt', function() {
diff --git a/test/identity.js b/test/identity.js
index 034cea4..a76fcaa 100644
--- a/test/identity.js
+++ b/test/identity.js
@@ -1,5 +1,5 @@
 var identity = require('../lib/identity')
-  , expect   = require('chai').expect
+  , expect   = require('must')
   , each     = require('../lib/each')
   , type     = require('../lib/type')
   , PI       = Math.PI
diff --git a/test/is.js b/test/is.js
index 40e984c..8147df1 100644
--- a/test/is.js
+++ b/test/is.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , range  = require('../lib/range')
   , each   = require('../lib/each')
   , seq    = require('../lib/seq')
diff --git a/test/isEmpty.js b/test/isEmpty.js
index 5e9569b..e825238 100644
--- a/test/isEmpty.js
+++ b/test/isEmpty.js
@@ -1,5 +1,5 @@
 var isEmpty = require('../lib/isEmpty')
-  , expect  = require('chai').expect
+  , expect  = require('must')
   , each    = require('../lib/each')
   , seq     = require('../lib/seq')
   , src     = require('../lib/src')
diff --git a/test/isnt.js b/test/isnt.js
index 7f5547a..2f7ddbd 100644
--- a/test/isnt.js
+++ b/test/isnt.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , isnt   = require('../lib/isnt')
   , each   = require('../lib/each')
   , src    = require('../lib/src')
diff --git a/test/lt.js b/test/lt.js
index 3c50276..d6b3b4e 100644
--- a/test/lt.js
+++ b/test/lt.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , lt     = require('../lib/lt')
 
 describe('lt', function() {
diff --git a/test/merge.js b/test/merge.js
index 8013f2b..f5dc46d 100644
--- a/test/merge.js
+++ b/test/merge.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , merge  = require('../lib/merge')
 
 describe('merge', function() {
@@ -8,7 +8,7 @@ describe('merge', function() {
         , bar = merge(foo)
 
       expect(foo).to.not.equal(bar)
-      expect(bar).to.have.key('wibble')
+      expect(bar).to.have.own('wibble')
       expect(bar.wibble).to.equal(1)
     })
   })
@@ -21,7 +21,7 @@ describe('merge', function() {
 
       expect(m).to.not.equal(a)
       expect(m).to.not.equal(b)
-      expect(m).to.have.keys('foo', 'bar')
+      expect(m).to.have.keys(['foo', 'bar'])
       expect(m.foo).to.equal(1)
       expect(m.bar).to.equal(2)
     })
@@ -31,7 +31,7 @@ describe('merge', function() {
         , b = { foo: 2, bar: 3 }
         , m = merge(a, b)
 
-      expect(m).to.have.keys('foo', 'bar')
+      expect(m).to.have.keys(['foo', 'bar'])
       expect(m.foo).to.equal(2)
       expect(m.bar).to.equal(3)
     })
@@ -47,7 +47,7 @@ describe('merge', function() {
       expect(m).to.not.equal(a)
       expect(m).to.not.equal(b)
       expect(m).to.not.equal(c)
-      expect(m).to.have.keys('foo', 'bar', 'baz')
+      expect(m).to.have.keys(['foo', 'bar', 'baz'])
       expect(m.foo).to.equal(1)
       expect(m.bar).to.equal(2)
       expect(m.baz).to.equal(3)
@@ -59,7 +59,7 @@ describe('merge', function() {
         , c = { baz: 5, foo: 6 }
         , m = merge(a, b, c)
 
-      expect(m).to.have.keys('foo', 'bar', 'baz')
+      expect(m).to.have.keys(['foo', 'bar', 'baz'])
       expect(m.foo).to.equal(6)
       expect(m.bar).to.equal(3)
       expect(m.baz).to.equal(5)
diff --git a/test/not.js b/test/not.js
index 751a27f..dc586bc 100644
--- a/test/not.js
+++ b/test/not.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , each   = require('../lib/each')
   , src    = require('../lib/src')
   , not    = require('../lib/not')
diff --git a/test/nth.js b/test/nth.js
index 03ccd58..a628f34 100644
--- a/test/nth.js
+++ b/test/nth.js
@@ -1,5 +1,5 @@
 var partial = require('../lib/partial')
-  , expect  = require('chai').expect
+  , expect  = require('must')
   , nth     = require('../lib/nth')
 
 describe('nth', function() {
diff --git a/test/once.js b/test/once.js
index 3f8f0cc..2fc107f 100644
--- a/test/once.js
+++ b/test/once.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , once   = require('../lib/once')
 
 describe('once', function() {
@@ -6,7 +6,7 @@ describe('once', function() {
     var ofn = once(fn)
 
     it('should return another function named `once`', function() {
-      expect(ofn).to.be.a('function')
+      expect(ofn).to.be.a(Function)
       expect(ofn.name).to.equal('once')
     })
 
diff --git a/test/partial.js b/test/partial.js
index cef630a..df132f5 100644
--- a/test/partial.js
+++ b/test/partial.js
@@ -1,4 +1,4 @@
-var expect = require("chai").expect
+var expect = require("must")
   , $      = require("../lib/partial") 
 
 describe("`partial`", function() {
diff --git a/test/pipe.js b/test/pipe.js
index 3b31bad..9866990 100644
--- a/test/pipe.js
+++ b/test/pipe.js
@@ -1,5 +1,5 @@
 var partial = require('../lib/partial')
-  , expect  = require('chai').expect
+  , expect  = require('must')
   , pipe    = require('../lib/pipe')
 
 describe('pipe', function() {
diff --git a/test/range.js b/test/range.js
index b61f915..f2df1fe 100644
--- a/test/range.js
+++ b/test/range.js
@@ -64,7 +64,7 @@ describe('range', function() {
   })
 })
 
-var expect = require('chai').expect
+var expect = require('must')
   , range  = require('../lib/range')
   , each   = require('../lib/each')
   , take   = require('../lib/take')
diff --git a/test/repeatedly.js b/test/repeatedly.js
index cc1f960..cb90ca0 100644
--- a/test/repeatedly.js
+++ b/test/repeatedly.js
@@ -1,6 +1,6 @@
 var repeatedly = require('../lib/repeatedly')
   , partial    = require('../lib/partial')
-  , expect     = require('chai').expect
+  , expect     = require('must')
   , range      = require('../lib/range')
   , each       = require('../lib/each')
   , nth        = require('../lib/nth')
diff --git a/test/seq.js b/test/seq.js
index 40e819c..25d1191 100644
--- a/test/seq.js
+++ b/test/seq.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , count  = require('../lib/count')
   , each   = require('../lib/each')
   , take   = require('../lib/take')
@@ -86,7 +86,7 @@ describe('seq', function() {
   describe('when given a string with unicode shenanigans', function() {
     it('should make a sequence of characters where code pairs are considered', function() {
       var chr = ['I', 'ñ', 't', 'ë', 'r', 'n', 'â', 't', 'i', 'ô', 'n', 'à', 'l', 'i', 'z', 'æ', 't', 'i', 'ø', 'n', '☃', '💩']
-          , str = seq(chr.join(''))
+        , str = seq(chr.join(''))
 
       expect(str.length).to.eql(chr.length)
 
@@ -114,7 +114,7 @@ describe('seq', function() {
       var s = seq(Math.random)
 
       each(take(5, s), function(n) {
-        expect(n).to.be.within(0, 1)
+        expect(n).to.be.between(0, 1)
       })
     })
   })
diff --git a/test/slice.js b/test/slice.js
index 20c018c..8a7b9e8 100644
--- a/test/slice.js
+++ b/test/slice.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , slice  = require('../lib/slice')
   , each   = require('../lib/each')
 
diff --git a/test/src.js b/test/src.js
index 7288f8c..17c456f 100644
--- a/test/src.js
+++ b/test/src.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , each   = require('../lib/each')
   , src    = require('../lib/src')
 
diff --git a/test/take.js b/test/take.js
index 4bcfdeb..c137d48 100644
--- a/test/take.js
+++ b/test/take.js
@@ -1,5 +1,5 @@
 var partial = require('../lib/partial')
-  , expect  = require('chai').expect
+  , expect  = require('must')
   , slice   = require('../lib/slice')
   , each    = require('../lib/each')
   , take    = require('../lib/take')
diff --git a/test/thunk.js b/test/thunk.js
index 4a7371c..92deea5 100644
--- a/test/thunk.js
+++ b/test/thunk.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , global = (function() { return this }())
   , thunk  = require('../lib/thunk')
   , each   = require('../lib/each')
@@ -10,7 +10,7 @@ describe('thunk', function() {
       it('should return a zero arity thunk', function() {
 	var th = thunk(function() {})
 
-        expect(th).to.be.a('function')
+        expect(th).to.be.a(Function)
         expect(th.length).to.equal(0)
         expect(th.name).to.equal('thunk')
       })
@@ -47,7 +47,7 @@ describe('thunk', function() {
           it('should return a zero arity thunk', function() {
 	    var th = thunk(function() {})
 
-            expect(th).to.be.a('function')
+            expect(th).to.be.a(Function)
             expect(th.length).to.equal(0)
           })
 
@@ -84,7 +84,7 @@ describe('thunk', function() {
     describe('and more than one parameter', function() {
       it('should return a zero arity function', function() {
 	var th = thunk(function() {}, 1, 2, 3)
-        expect(th).to.be.a('function')
+        expect(th).to.be.a(Function)
         expect(th.length).to.equal(0)
         expect(th.name).to.equal('thunk')
       })
@@ -217,7 +217,7 @@ describe('thunk', function() {
     it('should return a zero arity thunk', function() {
       var th = thunk(function() {})
 
-      expect(th).to.be.a('function')
+      expect(th).to.be.a(Function)
       expect(th.length).to.equal(0)
       expect(th.name).to.equal('thunk')
     })
diff --git a/test/trampoline.js b/test/trampoline.js
index 6438ce7..c3b313a 100644
--- a/test/trampoline.js
+++ b/test/trampoline.js
@@ -1,5 +1,5 @@
 var trampoline = require('../lib/trampoline')
-  , expect     = require('chai').expect
+  , expect     = require('must')
   , thunk      = require('../lib/thunk')
   , each       = require('../lib/each')
 
diff --git a/test/type.js b/test/type.js
index aea02e0..8dead7a 100644
--- a/test/type.js
+++ b/test/type.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , range  = require('../lib/range')
   , type   = require('../lib/type')
   , seq    = require('../lib/seq')
diff --git a/test/val.js b/test/val.js
index 366a11a..e80f94b 100644
--- a/test/val.js
+++ b/test/val.js
@@ -1,5 +1,5 @@
 var constantly = require('../lib/constantly')
-  , expect     = require('chai').expect
+  , expect     = require('must')
   , type       = require('../lib/type')
   , val        = require('../lib/val')
 
diff --git a/test/variadic.js b/test/variadic.js
index c53950a..1a31a02 100644
--- a/test/variadic.js
+++ b/test/variadic.js
@@ -1,5 +1,5 @@
 var variadic = require('../lib/variadic')
-  , expect   = require('chai').expect
+  , expect   = require('must')
   , thunk    = require('../lib/thunk')
   , range    = require('../lib/range')
   , slice    = require('../lib/slice')
diff --git a/test/vec.js b/test/vec.js
index 3d0c239..00b96bd 100644
--- a/test/vec.js
+++ b/test/vec.js
@@ -1,4 +1,4 @@
-var expect = require('chai').expect
+var expect = require('must')
   , range  = require('../lib/range')
   , each   = require('../lib/each')
   , type   = require('../lib/type')