jasmine/spies.html.md

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---
layout: default
title: Jasmine Spies
---
2010-09-18 07:02:58 +00:00
### Spies
Jasmine integrates 'spies' that permit many spying, mocking, and faking behaviors.
Here are a few examples:
var Klass = function () {
};
Klass.staticMethod = function (arg) {
return arg;
};
Klass.prototype.method = function (arg) {
return arg;
};
Klass.prototype.methodWithCallback = function (callback) {
return callback('foo');
};
...
describe("spy behavior", function() {
it('should spy on a static method of Klass', function() {
spyOn(Klass, 'staticMethod');
Klass.staticMethod('foo argument');
expect(Klass.staticMethod).toHaveBeenCalledWith('foo argument');
});
it('should spy on an instance method of a Klass', function() {
var obj = new Klass();
spyOn(obj, 'method');
obj.method('foo argument');
expect(obj.method).toHaveBeenCalledWith('foo argument');
var obj2 = new Klass();
spyOn(obj2, 'method');
expect(obj2.method).not.toHaveBeenCalled();
});
it('should spy on Klass#methodWithCallback', function() {
var callback = jasmine.createSpy();
new Klass().methodWithCallback(callback);
expect(callback).toHaveBeenCalledWith('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).not.toHaveBeenCalled();
var someResponseData = 'foo';
Klass.asyncMethod.mostRecentCall.args[0](someResponseData);
expect(callback).toHaveBeenCalledWith(someResponseData);
});
There are spy-specfic matchers that are very handy.
`expect(x).toHaveBeenCalled()` passes if `x` is a spy and was called
`expect(x).toHaveBeenCalledWith(arguments)` passes if `x` is a spy and was called with the specified arguments
`expect(x).not.toHaveBeenCalled()` passes if `x` is a spy and was not called
`expect(x).not.toHaveBeenCalledWith(arguments)` passes if `x` is a spy and was not called with the specified arguments
<small>The old matchers `wasCalled`, `wasNotCalled`, `wasCalledWith`, and `wasNotCalledWith` have been deprecated and will be removed in a future release. Please change your specs to use `toHaveBeenCalled`, `not.toHaveBeenCalled`, `toHaveBeenCalledWith`, and `not.toHaveBeenCalledWith` respectively.</small>
Spies can be trained to respond in a variety of ways when invoked:
`spyOn(x, 'method').andCallThrough()`: spies on AND calls the original function spied on
`spyOn(x, 'method').andReturn(arguments)`: returns passed arguments when spy is called
`spyOn(x, 'method').andThrow(exception)`: throws passed exception when spy is called
`spyOn(x, 'method').andCallFake(function)`: calls passed function when spy is called
Spies have some useful properties:
`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.