YET ANOTHER JavaScript testing framework
There are some situations when you want to test-drive JavaScript, but you don't want to be bothered with or even have an explicit document. You have no DOM to work with and thus lack HTML elements on which to hang event handlers. You may need to make asynchronous calls (say, to an AJAX API) and cannot mock/stub them.
But you still need to write tests.
What's an Agile Engineer to do?
Jasmine is yet another JavaScript testing framework. It's heavily influenced by JSSpec, ScrewUnit & JSpec, which are all influenced by RSpec. But each of those was lacking in some way: JSSpec & ScrewUnit require a DOM. JSpec's DOM-less assumption was a great start, but it needed asynchronous support.
So we started over. And TDD'd a whole new framework. Enjoy.
There is a nice example of how to use Jasmine in the /example directory. But here's more information.
Exciting changes are afoot and many syntax changes have been made to make Jasmine more usable. Please read the examples below for updates.
Each spec is, naturally, a JavaScript function. You tell Jasmine about this spec with a call to it() with a string and the function. The string is a description that will be helpful to you when reading a report.
it('should be a test', function () {
var foo = 0
foo++;
});
Within your spec you will want/need to make expectations. These are made with the expect() funciton and expectation matchers. like this:
it('should be a test', function () {
var foo = 0
foo++;
expect(foo).toEqual(1);
});
Results of the expectations are logged for later for reporting.
Jasmine has several built-in matchers. Here are a few:
toEqual() compares objects or primitives and returns true if they are equal
toNotEqual() compares objects or primitives and returns true if they are not equal
toMatch() takes a regex or a string and returns true if it matches
toNotMatch() takes a regex or a string and returns true if it does not match
toBeDefined() returns true if the object or primitive is not undefined
toBeNull() returns true if the object or primitive is not null
toBeTruthy() returns true if the object or primitive evaluates to true
toBeFalsy() returns true if the object or primitive evaluates to false
toContain() returns true if an array or string contains the passed variable.
toNotContain() returns true if an array or string does not contain the passed variable.
A Matcher has a method name, takes an expected value as it's only parameter, has access to the actual value in this, and then makes a call to this.report with true/false with a failure message. Here's the definition of toEqual():
Jasmine.Matchers.prototype.toEqual = function (expected) {
return this.report((this.actual === expected),
'Expected ' + expected + ' but got ' + this.actual + '.');
});
Feel free to define your own matcher as needed in your code. If you'd like to add Matchers to Jasmine, please write tests.
You may be thinking, "That's all well and good, but you mentioned something about asynchronous tests."
Well, say you need to make a call that is asynchronous - an AJAX API, or some other JavaScript library. That is, the call returns immediately, yet you want to make expectations 'at some point in the future' after some magic happens in the background.
Jasmine allows you to do this with runs() and waits() blocks.
runs() blocks by themselves simply run as if they were called directly. The following snippets of code should provide similar results:
it('should be a test', function () {
var foo = 0
foo++;
expect(foo).toEqual(1);
});
and
it('should be a test', function () {
runs( function () {
var foo = 0
foo++;
expect(foo).toEqual(1);
});
});
multiple runs() blocks in a spec will run serially. For example,
it('should be a test', function () {
runs( function () {
var foo = 0
foo++;
expect(foo).toEqual(1);
});
runs( function () {
var bar = 0
bar++;
expect(bar).toEqual(1);
});
});
runs() blocks share functional scope -- this properties will be common to all blocks, but declared var's will not!
it('should be a test', function () {
runs( function () {
this.foo = 0
this.foo++;
var bar = 0;
bar++;
expect(this.foo).toEqual(1);
expect(bar).toEqual(1);
});
runs( function () {
this.foo++;
var bar = 0
bar++;
expect(foo).toEqual(2);
expect(bar).toEqual(1);
});
});
runs() blocks exist so you can test asynchronous processes. The function waits() works with runs() to provide a naive
timeout before the next block is run. You supply a time to wait before the next runs() function is executed. For example:
it('should be a test', function () {
runs(function () {
this.foo = 0;
var that = this;
setTimeout(function () {
that.foo++;
}, 250);
});
runs(function () {
this.expects(this.foo).toEqual(0);
});
waits(500);
runs(function () {
this.expects(this.foo).toEqual(1);
});
});
What's happening here?
- The first call to
runs()sets call for 1/4 of a second in the future that incrementsthis.foo. - The second
runs()is executed immediately and then verifies thatthis.foowas indeed initialized to zero in the previousruns(). - Then we wait for half a second.
- Then the last call to
runs()expects thatthis.foowas incremented by thesetTimeout.
Specs are grouped in Suites. Suites are defined using the global describe() function:
describe('One suite', function () {
it('has a test', function () {
...
});
it('has another test', function () {
...
});
});
The Suite name is so that reporting is more descriptive.
Suites are executed in the order in which describe() calls are made, usually in the order in which their script files are included. Additionally, specs within a suite share a functional scope. So you may declare variables inside a describe block and they are accessible from within your specs. For example:
describe('A suite with some variables', function () {
var bar = 0
it('has a test', function () {
bar++;
expect(bar).toEqual(1);
});
it('has another test', function () {
bar++;
expect(bar).toEqual(2);
});
});
A suite can have a beforeEach declaration. It takes a function that is run before each spec. For example:
describe('some suite', function () {
var suiteWideFoo;
beforeEach(function () {
suiteWideFoo = 1;
}
it('should equal bar', function () {
expect(suiteWideFoo).toEqual(1);
};
});
Similarly, there is an afterEach declaration. It takes a function that is run after each spec. For example:
describe('some suite', function () {
var suiteWideFoo;
afterEach(function () {
suiteWideFoo = 0;
}
it('should equal 1', function () {
expect(suiteWideFoo).toEqual(1);
};
it('should equal 0 after', function () {
expect(suiteWideFoo).toEqual(0);
};
});
Jasmine supports nested describes. An example:
describe('some suite', function () {
var suiteWideFoo;
beforeEach(function () {
suiteWideFoo = 0;
});
describe('some nested suite', function() {
var nestedSuiteBar;
beforeEach(function() {
nestedSuiteBar=1;
});
it('nested expectation', function () {
expect(suiteWideFoo).toEqual(0);
expect(nestedSuiteBar).toEqual(1);
};
});
it('top-level describe', function () {
expect(suiteWideFoo).toEqual(0);
expect(nestedSuiteBar).toEqual(undefined);
};
});
Jasmine integrates 'spies' that permit many spying, mocking, and faking behaviors.
Here are a few examples:
var Klass = function () {
}
var Klass.prototype.method = function (arg) {
return arg;
}
var Klass.prototype.methodWithCallback = function (callback) {
return callback('foo');
}
...
it('should spy on Klass#method') {
spyOn(Klass, 'method');
Klass.method('foo argument');
expect(Klass.method).wasCalledWith('foo argument');
});
it('should spy on Klass#methodWithCallback') {
var callback = Jasmine.createSpy();
Klass.method(callback);
expect(callback).wasCalledWith('foo');
});
Spies can be very useful for testing AJAX or other asynchronous behaviors that take callbacks by faking the method firing an async call.
var Klass = function () {
};
var Klass.prototype.asyncMethod = function (callback) {
someAsyncCall(callback);
};
...
it('should test async call') {
spyOn(Klass, 'asyncMethod');
var callback = Jasmine.createSpy();
Klass.asyncMethod(callback);
expect(callback).wasNotCalled();
var someResponseData = 'foo';
Klass.asyncMethod.mostRecentCall.args[0](someResponseData);
expect(callback).wasCalledWith(someResponseData);
});
There are spy-specfic matchers that are very handy.
wasCalled() returns true if the object is a spy and was called
wasCalledWith(arguments) returns true if the object is a spy and was called with the passed arguments
wasNotCalled() returns true if the object is a spy and was not called
wasNotCalledWith(arguments) returns true if the object is a spy and was not called with the passed arguments
andCallThrough(): spies on AND calls the original function spied on
andReturn(arguments): returns passed arguments when spy is called
andThrow(exception): throws passed exception when spy is called
andCallFake(function): calls passed function when spy is called
callCount: returns number of times spy was called
mostRecentCall.args: returns argument array from last call to spy.
argsForCall[i] returns arguments array for call i to spy.
Spies are automatically removed after each spec. They may be set in the beforeEach function.
You don't need a DOM to run your tests, but you do need a page on which to load & execute your JS. Include the jasmine.js file in a script tag as well as the JS file with your specs. You can also use this page for reporting. More on that in a moment.
Here's the example HTML file (in jasmine/example):
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Jasmine Example</title>
<script type="text/javascript" src="../lib/jasmine.js"></script>
<script type="text/javascript" src="example.js"></script>
<link type="text/css" rel="stylesheet" href="../lib/jasmine.css"/>
</head>
<body>
<h1>
Running Jasmine Example Specs
</h1>
<div id="results"></div>
<script type="text/javascript">
jasmine.execute();
setTimeout(function () {
document.getElementById('results').innerHTML = 'It\'s alive! :' +
(jasmine.currentRunner.results.passedCount === 1);
}, 250);
</script>
</body>
</html>
It's the call to jasmine.execute() that runs all of the defined specs, gathering reports of each expectation.
If a reporter exists on the Jasmine instance (named jasmine), it will be called when each spec, suite and the overall runner complete. If you're at the single-spec result level, you'll get a spec description, whether it passed or failed, and what the failure message was. At the suite & runner report level, you'll get the total specs run so far, the passed counts, failed counts, and a description (of the suite or runner).
There is a Jasmine.Reporters namespace for you to see how to handle reporting. See the file json_reporter.js, which takes the results objects and turns them into JSON strings, for two examples of how to make the results callbacks work for you.
Specs may be disabled by calling xit() instead of it(). Suites may be disabled by calling xdescribe() instead of describe(). A simple find/replace in your editor of choice will allow you to run a subset of your specs.
Sometimes it's hard to test a framework with the framework itself. Either the framework isn't mature enough or it just hurts your head. Jasmine is affected by both.
So we made a little bootstrappy test reporter that lets us test Jasmine's pieces in isolation. See test/bootstrap.js. Feel free to use the bootstrap test suite to test your custom Matchers or extensions/changes to Jasmine.
Your contributions are welcome. Please submit tests with your pull request.
We now have a Google Group for support & discussion.
- Homepage: http://groups.google.com/group/jasmine-js
- Group email: [email protected]
- Davis W. Frank, Pivotal Labs
- Rajan Agaskar, Pivotal Labs
- A big shout out to the various JavaScript test framework authors, especially TJ for JSpec - we played with it a bit before deciding that we really needed to roll our own.
- Thanks to Pivot Jessica Miller for our fancy pass/fail/pending icons
- Huge contributions have been made by Christian Williams (the master "spy" coder), Erik Hanson, Adam Abrons and Carl Jackson, and many other Pivots.
- Pending & Disabled counts should be included in results
- BUG: describe blocks can't be empty - specs will stall