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simple-mock

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Super simple stubs and spies with 1-step sandbox restore

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# simple-mock

[![travis][travis-image]][travis-url]
[![npm][npm-image]][npm-url]
[![downloads][downloads-image]][downloads-url]

[travis-image]: https://img.shields.io/travis/jupiter/simple-mock.svg?style=flat
[travis-url]: https://travis-ci.org/jupiter/simple-mock
[npm-image]: https://img.shields.io/npm/v/simple-mock.svg?style=flat
[npm-url]: https://npmjs.org/package/simple-mock
[downloads-image]: https://img.shields.io/npm/dm/simple-mock.svg?style=flat
[downloads-url]: https://npmjs.org/package/simple-mock

Super simple stubs and spies with 1-step sandbox restore.

## Install

For Node:

```
$ npm install simple-mock
```

For Browser:

```
$ bower install simple-mock
```

## Mock

Not sure when to use a mock, stub, or spy? Just use `simple.mock`.

Examples:

```js
var simple = require('simple-mock')

simple.mock(obj, 'example', 'value') // Replace with this value

simple.mock(obj, 'example') // Spy on underlying method *or* stub
simple.mock(obj, 'example').callFn(function () {}) // Stub
simple.mock(obj, 'example').callbackWith(null, 'etc') // Stub
simple.mock(obj, 'example').returnWith('etc') // Stub
simple.mock(obj, 'example').throwWith(new Error()) // Stub
simple.mock(obj, 'example').resolveWith('etc') // Stub
simple.mock(obj, 'example').rejectWith(new Error()) // Stub
simple.mock(obj, 'example').callOriginal() // Unstubbed call
```

Then, to make sure all objects are back to the state the were in before your mocks:

```js
simple.restore() // Ideally called in an afterEach() block
```

`callbackWith`, `returnWith` and `throwWith` can be chained for queued behaviour, e.g.

```js
simple.mock(Something.prototype, 'example')
  .callbackWith(null, 'etc')
  .callbackWith(new Error())
```

`callbackWith`, `returnWith` and `throwWith` configurations are stored on a simple array fn.actions

## Expectations

You define your expectations with *your own choice* of assertion library.

```js
assert(fn.called)
assert.equals(fn.callCount, 3)
assert.equals(fn.lastCall.arg, error) // First parameter of the last call
assert.equals(fn.lastCall.args[1], 'etc') // Second parameter of the last call
assert.equals(fn.calls[0].returned, 'etc')
assert.equals(fn.calls[1].threw, error)
```

## Standalone Stubs and Spies

If you need to create a standalone stub (stubs are also spies):

```js
var fn = simple.stub().returnWith('etc')

var returned = fn()

assert.equals(returned, 'etc')
```

Or spy on a standalone function:

```js
var fn = simple.spy(function () {})

assert.equals(fn.callCount, 0)
assert.equals(fn.calls, [])
```

See [examples](examples) for more common usage patterns.

## API

For `var simple = require('simple-mock')`:

### simple.mock(obj, key, value)

Sets the value on this object. E.g. `mock(config, 'title', 'test')` is the same as `config.title = 'test'`, but restorable with all mocks.

### simple.mock(obj, key, fn)

Wraps `fn` in a spy and sets this on the `obj`, restorable with all mocks.

### simple.mock(obj, key)

If `obj` has already has this function, it is wrapped in a spy. The resulting spy can be turned into a stub by further configuration. Restores with all mocks.

### simple.restore()

Restores all current mocks.

### simple.restore(obj, key)

Use this if you need to restore only a single mock value or function on an object.

### simple.spy(fn) *or* simple.mock(fn)

Wraps `fn` in a spy.

### simple.stub() *or* simple.mock()

Returns a stub function that is also a spy.

---

### spy.called

Boolean

### spy.callCount

Number of times the function was called.

### spy.calls

An array of calls, each having these properties:

- **call.args** an array of arguments received on the call
- **call.context** the context (`this`) of the call
- **call.returned** the value returned by the wrapped function
- **call.threw** the error thrown by the wrapped function
- **call.k** autoincrementing number, can be compared to evaluate call order

### spy.lastCall

The last call object, with properties as above. (This is often also the first and only call.)

### spy.reset()

Resets all counts and properties to the original state.

---

### stub.callFn(fn)

Configures this stub to call this function, returning its return value. Subsequent calls of this on the same stub (chainable) will queue up different behaviours for each subsequent call of the stub.

### stub.callOriginal()

Configures this stub to call the original, unstubbed function, returning its return value. Subsequent calls of this on the same stub (chainable) will queue up different behaviours for each subsequent call of the stub.

### stub.returnWith(val)

Configures this stub to return with this value. Subsequent calls of this on the same stub (chainable) will queue up different behaviours for each subsequent call of the stub.

### stub.throwWith(err)

Configures this stub to throw this error. Subsequent calls of this on the same stub (chainable) will queue up different behaviours for each subsequent call of the stub.

### stub.callback(...) *or* stub.callbackAtIndex(cbArgumentIndex, ...)

Configures this stub to call back with the arguments passed. It will use either the last argument as callback, or the argument at `cbArgumentIndex`. Subsequent calls of this on the same stub (chainable) will queue up different behaviours for each subsequent call of the stub.

### stub.inThisContext(obj)

Configures the last configured function or callback to be called in this context, i.e. `this` will be `obj`.

### stub.resolveWith(val)

Configures the stub to return a Promise (where available] resolving to this value. Same as `stub.returnWith(Promise.resolve(val))`. You can use a custom Promise-conforming library, i.e. `simple.Promise = require('bluebird')` or `simple.Promise = $q`.

### stub.rejectWith(val)

Configures the stub to return a Promise (where available) rejecting with this error. Same as `stub.returnWith(Promise.reject(val))`. You can use a custom Promise-conforming library, i.e. `simple.Promise = require('bluebird')` or `simple.Promise = $q`.

### stub.actions

An array of behaviours, each having *one* of these properties:

- **action.cbArgs** arguments to call back with
- **action.returnValue**
- **action.throwError**

Note: modifying this array directly is not supported, rather use stub.withActions(actions) if you need to add actions.

### stub.withActions(actions) *or* stub.withActions()

Configures this stub to use the specified array of actions. See `stub.actions` above for the syntax of an action.

```js
var fn = simple.stub()
         .returnWith('a')
         .withActions([{ returnValue: 'b' }, { returnValue: 'c' }])
         .returnWith('d')

var returned1 = fn()
var returned2 = fn()
var returned3 = fn()
var returned4 = fn()

assert.equal(fn.callCount, 4)
assert.equal(returned1, 'a')
assert.equal(returned2, 'b')
assert.equal(returned3, 'c')
assert.equal(returned4, 'd')
```

### stub.loop

Boolean (default: true) setting whether the queue of actions for this stub should repeat.

### stub.withLoop() & stub.noLoop()

Configures the stub to enable/disable [looping](#stubloop).

## Why

The most complete, framework-agnostic mocking library is [sinon.js](http://sinonjs.org/). It also has pages of documentation and lots of sugar-coating that we generally don't need. Keep it simple!

simple-mock

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