chai-changes
chai-changes is an extension to the chai assertion library that
provides a set of change-specific assertions.
Usage
Include chai-changes.js
in your test file, after chai.js
(version 1.0.0-rc1 or later):
<script src="chai-changes.js"></script>
Use the assertions with chai's expect
or should
assertions.
Assertions
All assertions use a when
mechanism.
Using 'expect':
expect(-> codeThatYieldsAChangedResult).to....when ->
executeTheCodeThatCausesTheChange()
The code within the expect
section will be executed first, then the
code in the when
section will be executed and then the code in the
expect
section will be executed again and the differences will be
asserted.
Same test using 'should':
(-> codeThatYieldsAChangedResult).should....when ->
executeTheCodeThatCausesTheChange()
when
Executes the build up pre- and post-conditions. First it executes the
pre-conditions, then it will execute the provided callback. And after
the callback it will assert the post-conditions. It will change the
object in the assertion chain to the result of the callback.
When the callback returns a promise, the post-conditions are executed
when the promise is fulfilled.
Since the 'object' in the assertion chain is changed after the when, you
can chain chai-as-promised matchers too, like:
(-> result).should.change.to(4).when(-> object.methodThatReturnsPromise()).and.notify(done)
This makes this mechanism also compatible with
mocha-as-promised
change
Assert if the 'expect/should' changes its outcome when 'when' is
executed
result = 0
(-> result).should.change.when -> result += 1
expect(-> result).to.change.when -> result -= 1
expect(-> result).not.to.change.when -> result = result * 1
change.by(delta)
Assert if the change of the 'expect/should' has the provided delta
result = 0
(-> result).should.change.by(3).when -> result += 3
expect(-> result).not.to.change.by(-3).when -> result += 1
expect(-> result).to.change.by(-2).when -> result -= 2
change.from(startValue)
Assert if the change starts from a certain value. The value is
compared using a deep equal.
result = ['a', 'b']
(-> result).should.change.from(['a', 'b']).when -> result.push('c')
(-> result).should.change.from(['a', 'b']).to(['a', 'b', 'c']).when -> result.push('c')
change.to(endValue)
Assert if the change ends in a certain value. The value is
compared using a deep equal.
result = ['a', 'b']
(-> result).should.change.to(['a', 'b', 'c']).when -> result.push('c')
(-> result).should.change.from(['a', 'b']).to(['a', 'c']).when -> result = ['a', 'c']
License
Copyright (c) 2012 Matthijs Groen
MIT License (see the LICENSE file)