diff --git a/index.js b/index.js
index 15e3c2e..9a8929c 100644
--- a/index.js
+++ b/index.js
@@ -5,11 +5,13 @@ module.exports =
   , compose    : require('./lib/compose')
   , constantly : require('./lib/constantly')
   , count      : require('./lib/count')
+  , dec        : require('./lib/dec')
   , each       : require('./lib/each')
   , eq         : require('./lib/eq')
   , gt         : require('./lib/gt')
   , get        : require('./lib/get')
   , identity   : require('./lib/identity')
+  , inc        : require('./lib/inc')
   , is         : require('./lib/is')
   , isEmpty    : require('./lib/isEmpty')
   , isnt       : require('./lib/isnt')
diff --git a/lib/dec.js b/lib/dec.js
new file mode 100644
index 0000000..d32e783
--- /dev/null
+++ b/lib/dec.js
@@ -0,0 +1,13 @@
+module.exports = dec
+
+function dec(x) {
+  var n = val(x)
+
+  assert(is(Number, n), "Expected number, got: " + x)
+
+  return n - 1
+}
+
+var assert = require('./assert')
+  , val    = require('./val')
+  , is     = require('./is')
\ No newline at end of file
diff --git a/lib/inc.js b/lib/inc.js
new file mode 100644
index 0000000..8c54410
--- /dev/null
+++ b/lib/inc.js
@@ -0,0 +1,13 @@
+module.exports = inc
+
+function inc(x) {
+  var n = val(x)
+
+  assert(is(Number, n), "Expected number, got: " + x)
+
+  return n + 1
+}
+
+var assert = require('./assert')
+  , val    = require('./val')
+  , is     = require('./is')
\ No newline at end of file
diff --git a/test/dec.js b/test/dec.js
new file mode 100644
index 0000000..fe4d20f
--- /dev/null
+++ b/test/dec.js
@@ -0,0 +1,31 @@
+var constantly = require('../lib/constantly')
+  , expect     = require('must')
+  , range      = require('../lib/range')
+  , each       = require('../lib/each')
+  , dec        = require('../lib/dec')
+  , $          = require('../lib/partial')
+
+describe('dec', function() {
+  describe('when given a number `n`', function() {
+    it('should decrement that number by one and return the result', function() {
+      each(range(100), function(n) {
+        expect(dec(n)).to.equal(n - 1)
+      })
+    })
+  })
+
+  describe('when given a function', function() {
+    it('should call the function and try to decrement the return value', function() {
+      var three = constantly(3)
+      expect(dec(three)).to.equal(2)
+    })
+  })
+
+  describe('when given a value that is not a number', function() {
+    it('should throw', function() {
+      each([ 'foo', true, false, null, undefined, NaN ], function(x) {
+        expect($(dec, x)).to.throw()
+      })
+    })
+  })
+})
\ No newline at end of file
diff --git a/test/funkis.js b/test/funkis.js
index d61874e..d3021fc 100644
--- a/test/funkis.js
+++ b/test/funkis.js
@@ -2,14 +2,16 @@ var fs     = require('fs')
   , path   = require('path')
   , each   = require('../lib/each')
   , funkis = require('../')
-  , expect = require('expect.js')
+  , expect = require('must')
 
 describe('funkis', function() {
   it('should export every function in lib/', function() {
-    var names = fs.readdirSync(path.join(__dirname, '../lib'))
-      .map(function(file) {
-        var module = path.basename(file, '.js')
-        expect(funkis).to.have.key(module)
-      })
+    var names = fs.readdirSync(path.join(__dirname, '../lib')).map(function(file) {
+      return path.basename(file, '.js')
+    })
+
+    each(names, function(name) {
+      expect(funkis).to.have.property(name)
+    })
   })
 })
\ No newline at end of file
diff --git a/test/inc.js b/test/inc.js
new file mode 100644
index 0000000..5b1c2bc
--- /dev/null
+++ b/test/inc.js
@@ -0,0 +1,31 @@
+var constantly = require('../lib/constantly')
+  , expect     = require('must')
+  , range      = require('../lib/range')
+  , each       = require('../lib/each')
+  , inc        = require('../lib/inc')
+  , $          = require('../lib/partial')
+
+describe('inc', function() {
+  describe('when given a number `n`', function() {
+    it('should increment that number by one and return the result', function() {
+      each(range(100), function(n) {
+        expect(inc(n)).to.equal(n + 1)
+      })
+    })
+  })
+
+  describe('when given a function', function() {
+    it('should call the function and try to increment the return value', function() {
+      var three = constantly(3)
+      expect(inc(three)).to.equal(4)
+    })
+  })
+
+  describe('when given a value that is not a number', function() {
+    it('should throw', function() {
+      each([ 'foo', true, false, null, undefined, NaN ], function(x) {
+        expect($(inc, x)).to.throw()
+      })
+    })
+  })
+})
\ No newline at end of file