diff --git a/object.js b/object.js
index 54ab830..6f0d8c9 100644
--- a/object.js
+++ b/object.js
@@ -1,12 +1,17 @@
 
-export const create = Object.create(null)
+/**
+ * @return {Object<string,any>} obj
+ */
+export const create = () => Object.create(null)
 
+/**
+ * @param {Object<string,any>} obj
+ */
 export const keys = Object.keys
 
 /**
- * @template V
- * @param {Object<string,V>} obj
- * @param {function(V,string):any} f
+ * @param {Object<string,any>} obj
+ * @param {function(any,string):any} f
  */
 export const forEach = (obj, f) => {
   for (let key in obj) {
@@ -14,6 +19,12 @@ export const forEach = (obj, f) => {
   }
 }
 
+/**
+ * @template R
+ * @param {Object<string,any>} obj
+ * @param {function(any,string):R} f
+ * @return {Array<R>}
+ */
 export const map = (obj, f) => {
   const results = []
   for (let key in obj) {
@@ -22,8 +33,31 @@ export const map = (obj, f) => {
   return results
 }
 
-export const length = obj => Object.keys(obj).length
+/**
+ * @param {Object<string,any>} obj
+ * @return {number}
+ */
+export const length = obj => keys(obj).length
+
+/**
+ * @param {Object<string,any>} obj
+ * @param {function(any,string):boolean} f
+ * @return {boolean}
+ */
+export const some = (obj, f) => {
+  for (let key in obj) {
+    if (f(obj[key], key)) {
+      return true
+    }
+  }
+  return false
+}
 
+/**
+ * @param {Object<string,any>} obj
+ * @param {function(any,string):boolean} f
+ * @return {boolean}
+ */
 export const every = (obj, f) => {
   for (let key in obj) {
     if (!f(obj[key], key)) {
@@ -33,6 +67,9 @@ export const every = (obj, f) => {
   return true
 }
 
-export const some = (obj, f) => every(obj, () => !f())
-
-export const equalFlat = (a, b) => a === b || (length(a) === length(b) && every(a, (val, key) => b[key] === val))
+/**
+ * @param {Object<string,any>} a
+ * @param {Object<string,any>} b
+ * @return {boolean}
+ */
+export const equalFlat = (a, b) => a === b || (length(a) === length(b) && every(a, (val, key) => (val !== undefined || b.hasOwnProperty(key)) && b[key] === val))
diff --git a/object.test.js b/object.test.js
new file mode 100644
index 0000000..d4fea83
--- /dev/null
+++ b/object.test.js
@@ -0,0 +1,31 @@
+import * as t from './testing.js'
+import * as object from './object.js'
+import * as math from './math.js'
+
+export const testObject = tc => {
+  t.assert(object.create().constructor === undefined, 'object.create creates an empty object without constructor')
+  t.describe('object.equalFlat')
+  t.assert(object.equalFlat({}, {}), 'comparing equal objects')
+  t.assert(object.equalFlat({ 'x': 1 }, { 'x': 1 }), 'comparing equal objects')
+  t.assert(object.equalFlat({ x: 'dtrn' }, { x: 'dtrn' }), 'comparing equal objects')
+  t.assert(!object.equalFlat({ x: {} }, { x: {} }), 'flatEqual does not dive deep')
+  t.assert(object.equalFlat({ x: undefined }, { x: undefined }), 'flatEqual handles undefined')
+  t.assert(!object.equalFlat({ x: undefined }, { y: {} }), 'flatEqual handles undefined')
+  t.describe('object.every')
+  t.assert(object.every({ a: 1, b: 3 }, (v, k) => (v % 2) === 1 && k !== 'c'))
+  t.assert(!object.every({ a: 1, b: 3, c: 5 }, (v, k) => (v % 2) === 1 && k !== 'c'))
+  t.describe('object.some')
+  t.assert(object.some({ a: 1, b: 3 }, (v, k) => v === 3 && k === 'b'))
+  t.assert(!object.some({ a: 1, b: 5 }, (v, k) => v === 3))
+  t.assert(object.some({ a: 1, b: 5 }, () => true))
+  t.assert(!object.some({ a: 1, b: 5 }, (v, k) => false))
+  t.describe('object.forEach')
+  let forEachSum = 0
+  object.forEach({ x: 1, y: 3 }, (v, k) => { forEachSum += v })
+  t.assert(forEachSum === 4)
+  t.describe('object.map')
+  t.assert(object.map({ x: 1, z: 5 }, (v, k) => v).reduce(math.add) === 6)
+  t.describe('object.length')
+  t.assert(object.length({}) === 0)
+  t.assert(object.length({ x: 1 }) === 1)
+}
diff --git a/test.js b/test.js
index 80ad944..8d32fd2 100644
--- a/test.js
+++ b/test.js
@@ -16,6 +16,7 @@ import * as map from './map.test.js'
 import * as eventloop from './eventloop.test.js'
 import * as time from './time.test.js'
 import * as pair from './pair.test.js'
+import * as object from './object.test.js'
 
 import { isBrowser, isNode } from './environment.js'
 
@@ -39,7 +40,8 @@ runTests({
   map,
   eventloop,
   time,
-  pair
+  pair,
+  object
 }).then(success => {
   /* istanbul ignore next */
   if (isNode) {
diff --git a/testing.js b/testing.js
index bb524e1..2ae968c 100644
--- a/testing.js
+++ b/testing.js
@@ -235,7 +235,12 @@ const _compare = (a, b, path, message, customCompare) => {
       if (object.length(a) !== object.length(b)) {
         _failMessage(message, 'Objects have a different number of attributes', path)
       }
-      object.forEach(a, (value, key) => _compare(value, b[key], `${path}["${key}"]`, message, customCompare))
+      object.forEach(a, (value, key) => {
+        if (!b.hasOwnProperty(key)) {
+          _failMessage(message, `Property ${path} does not exist on second argument`, path)
+        }
+        b.hasOwnProperty(key) && _compare(value, b[key], `${path}["${key}"]`, message, customCompare)
+      })
       break
     case Array:
       if (a.length !== b.length) {
@@ -260,14 +265,18 @@ export const assert = (condition, message = null) => condition
   ? (message !== null && log.print(log.GREEN, log.BOLD, '√ ', log.UNBOLD, message))
   : fail(message ? `Failed condition: ${message}` : 'Assertion failed')
 
-export const fails = (f, message) => {
+export const fails = f => {
   let err = null
   try {
     f()
   } catch (_err) {
     err = _err
+    log.print(log.GREEN, '⇖ This Error was expected')
+  }
+  /* istanbul ignore if */
+  if (err === null) {
+    fail('Expected this to fail')
   }
-  assert(err !== null, message)
 }
 
 /**
diff --git a/testing.test.js b/testing.test.js
index 9fc7dd9..20a2c91 100644
--- a/testing.test.js
+++ b/testing.test.js
@@ -8,9 +8,16 @@ export const testComparing = () => {
   t.compare([1, 2], [1, 2], 'simple compare (array)')
   t.compare({ a: [1, 2] }, { a: [1, 2] }, 'simple compare nested')
 
+  t.describe('The following errors are expected!')
   t.fails(() => {
     t.compare({ a: 4 }, { b: 5 }, 'childs are not equal')
   })
+  t.fails(() => {
+    t.compare({ a: 4 }, { a: 5 }, 'childs are not equal')
+  })
+  t.fails(() => {
+    t.compare({ a: 4 }, null, 'childs are not equal')
+  })
   t.fails(() => {
     t.compare({ a: 4 }, [4], 'childs have different types')
   })
@@ -40,6 +47,12 @@ export const testComparing = () => {
   t.fails(() => {
     t.compareObjects({ x: 3 }, { x: 1 }) // Compare different objects -- no message
   })
+  t.fails(() => {
+    t.compare({ x: undefined }, { y: 1 }, 'compare correctly handles undefined')
+  })
+  t.fails(() => {
+    t.compareObjects({ x: undefined }, { y: 1 }, 'compare correctly handles undefined')
+  })
 }
 
 export const testFailing = () => {