Documentation Home Behavior-Driven JavaScript
This page is for an older version of Jasmine (2.0)
The current stable version of Jasmine is: 5.5 - You can also look at the docs for the next release: Edge

introduction.js

Jasmine is a behavior-driven development framework for testing JavaScript code. It does not depend on any other JavaScript frameworks. It does not require a DOM. And it has a clean, obvious syntax so that you can easily write tests. This guide is running against Jasmine version FILLED IN AT RUNTIME.

Standalone Distribution

The releases page has links to download the standalone distribution, which contains everything you need to start running Jasmine. After downloading a particular version and unzipping, opening SpecRunner.html will run the included specs. You'll note that both the source files and their respective specs are linked in the <head> of the SpecRunner.html. To start using Jasmine, replace the source/spec files with your own.

Suites: describe Your Tests

A test suite begins with a call to the global Jasmine function describe with two parameters: a string and a function. The string is a name or title for a spec suite - usually what is being tested. The function is a block of code that implements the suite.

Specs

Specs are defined by calling the global Jasmine function it, which, like describe takes a string and a function. The string is the title of the spec and the function is the spec, or test. A spec contains one or more expectations that test the state of the code. An expectation in Jasmine is an assertion that is either true or false. A spec with all true expectations is a passing spec. A spec with one or more false expectations is a failing spec.

 
describe("A suite", function() {
it("contains spec with an expectation", function() {
  expect(true).toBe(true);
});
});

It's Just Functions

Since describe and it blocks are functions, they can contain any executable code necessary to implement the test. JavaScript scoping rules apply, so variables declared in a describe are available to any it block inside the suite.

 
describe("A suite is just a function", function() {
var a;

it("and so is a spec", function() {
  a = true;

  expect(a).toBe(true);
});
});

Expectations

Expectations are built with the function expect which takes a value, called the actual. It is chained with a Matcher function, which takes the expected value.

 
describe("The 'toBe' matcher compares with ===", function() {

Matchers

Each matcher implements a boolean comparison between the actual value and the expected value. It is responsible for reporting to Jasmine if the expectation is true or false. Jasmine will then pass or fail the spec.

 
  it("and has a positive case", function() {
  expect(true).toBe(true);
});

Any matcher can evaluate to a negative assertion by chaining the call to expect with a not before calling the matcher.

 
  it("and can have a negative case", function() {
  expect(false).not.toBe(true);
});
});

Included Matchers

Jasmine has a rich set of matchers included. Each is used here - all expectations and specs pass. There is also the ability to write custom matchers for when a project's domain calls for specific assertions that are not included below.

 
describe("Included matchers:", function() {

it("The 'toBe' matcher compares with ===", function() {
  var a = 12;
  var b = a;

  expect(a).toBe(b);
  expect(a).not.toBe(null);
});

describe("The 'toEqual' matcher", function() {

  it("works for simple literals and variables", function() {
    var a = 12;
    expect(a).toEqual(12);
  });

  it("should work for objects", function() {
    var foo = {
      a: 12,
      b: 34
    };
    var bar = {
      a: 12,
      b: 34
    };
    expect(foo).toEqual(bar);
  });
});

it("The 'toMatch' matcher is for regular expressions", function() {
  var message = "foo bar baz";

  expect(message).toMatch(/bar/);
  expect(message).toMatch("bar");
  expect(message).not.toMatch(/quux/);
});

it("The 'toBeDefined' matcher compares against `undefined`", function() {
  var a = {
    foo: "foo"
  };

  expect(a.foo).toBeDefined();
  expect(a.bar).not.toBeDefined();
});

it("The `toBeUndefined` matcher compares against `undefined`", function() {
  var a = {
    foo: "foo"
  };

  expect(a.foo).not.toBeUndefined();
  expect(a.bar).toBeUndefined();
});

it("The 'toBeNull' matcher compares against null", function() {
  var a = null;
  var foo = "foo";

  expect(null).toBeNull();
  expect(a).toBeNull();
  expect(foo).not.toBeNull();
});

it("The 'toBeTruthy' matcher is for boolean casting testing", function() {
  var a, foo = "foo";

  expect(foo).toBeTruthy();
  expect(a).not.toBeTruthy();
});

it("The 'toBeFalsy' matcher is for boolean casting testing", function() {
  var a, foo = "foo";

  expect(a).toBeFalsy();
  expect(foo).not.toBeFalsy();
});

describe("The 'toContain' matcher", function() {
  it("works for finding an item in an Array", function() {
    var a = ["foo", "bar", "baz"];

    expect(a).toContain("bar");
    expect(a).not.toContain("quux");
  });

  it("also works for finding a substring", function() {
    var a = "foo bar baz";

    expect(a).toContain("bar");
    expect(a).not.toContain("quux");
  });
});

it("The 'toBeLessThan' matcher is for mathematical comparisons", function() {
  var pi = 3.1415926,
    e = 2.78;

  expect(e).toBeLessThan(pi);
  expect(pi).not.toBeLessThan(e);
});

it("The 'toBeGreaterThan' matcher is for mathematical comparisons", function() {
  var pi = 3.1415926,
    e = 2.78;

  expect(pi).toBeGreaterThan(e);
  expect(e).not.toBeGreaterThan(pi);
});

it("The 'toBeCloseTo' matcher is for precision math comparison", function() {
  var pi = 3.1415926,
    e = 2.78;

  expect(pi).not.toBeCloseTo(e, 2);
  expect(pi).toBeCloseTo(e, 0);
});

it("The 'toThrow' matcher is for testing if a function throws an exception", function() {
  var foo = function() {
    return 1 + 2;
  };
  var bar = function() {
    return a + 1;
  };
  var baz = function() {
    throw 'what';
  };

  expect(foo).not.toThrow();
  expect(bar).toThrow();
  expect(baz).toThrow('what');
});

it("The 'toThrowError' matcher is for testing a specific thrown exception", function() {
  var foo = function() {
    throw new TypeError("foo bar baz");
  };

  expect(foo).toThrowError("foo bar baz");
  expect(foo).toThrowError(/bar/);
  expect(foo).toThrowError(TypeError);
  expect(foo).toThrowError(TypeError, "foo bar baz");
});
});

Setup and Teardown

To help a test suite DRY up any duplicated setup and teardown code, Jasmine provides the global beforeEach and afterEach functions. As the name implies, the beforeEach function is called once before each spec in the describe in which it is called, and the afterEach function is called once after each spec. Here is the same set of specs written a little differently. The variable under test is defined at the top-level scope -- the describe block -- and initialization code is moved into a beforeEach function. The afterEach function resets the variable before continuing.

 
describe("A spec (with setup and tear-down)", function() {
var foo;

beforeEach(function() {
  foo = 0;
  foo += 1;
});

afterEach(function() {
  foo = 0;
});

it("is just a function, so it can contain any code", function() {
  expect(foo).toEqual(1);
});

it("can have more than one expectation", function() {
  expect(foo).toEqual(1);
  expect(true).toEqual(true);
});
});

The this keyword

Another way to share variables between a beforeEach, it, and afterEach is through the this keyword. Each spec's beforeEach/it/afterEach has the this as the same empty object that is set back to empty for the next spec's beforeEach/it/afterEach.

 
describe("A spec", function() {
beforeEach(function() {
  this.foo = 0;
});

it("can use the `this` to share state", function() {
  expect(this.foo).toEqual(0);
  this.bar = "test pollution?";
});

it("prevents test pollution by having an empty `this` created for the next spec", function() {
  expect(this.foo).toEqual(0);
  expect(this.bar).toBe(undefined);
});
});

Nesting describe Blocks

Calls to describe can be nested, with specs defined at any level. This allows a suite to be composed as a tree of functions. Before a spec is executed, Jasmine walks down the tree executing each beforeEach function in order. After the spec is executed, Jasmine walks through the afterEach functions similarly.

 
describe("A spec", function() {
var foo;

beforeEach(function() {
  foo = 0;
  foo += 1;
});

afterEach(function() {
  foo = 0;
});

it("is just a function, so it can contain any code", function() {
  expect(foo).toEqual(1);
});

it("can have more than one expectation", function() {
  expect(foo).toEqual(1);
  expect(true).toEqual(true);
});

describe("nested inside a second describe", function() {
  var bar;

  beforeEach(function() {
    bar = 1;
  });

  it("can reference both scopes as needed", function() {
    expect(foo).toEqual(bar);
  });
});
});

Disabling Suites

Suites can be disabled with the xdescribe function. These suites and any specs inside them are skipped when run and thus their results will not appear in the results.

 
xdescribe("A spec", function() {
var foo;

beforeEach(function() {
  foo = 0;
  foo += 1;
});

it("is just a function, so it can contain any code", function() {
  expect(foo).toEqual(1);
});
});

Pending Specs

Pending specs do not run, but their names will show up in the results as pending.

 
describe("Pending specs", function() {

Any spec declared with xit is marked as pending.

 
  xit("can be declared 'xit'", function() {
  expect(true).toBe(false);
});

Any spec declared without a function body will also be marked pending in results.

 
  it("can be declared with 'it' but without a function");

And if you call the function pending anywhere in the spec body, no matter the expectations, the spec will be marked pending.

 
  it("can be declared by calling 'pending' in the spec body", function() {
  expect(true).toBe(false);
  pending();
});
});

Spies

Jasmine has test double functions called spies. A spy can stub any function and tracks calls to it and all arguments. A spy only exists in the describe or it block in which it is defined, and will be removed after each spec. There are special matchers for interacting with spies. This syntax has changed for Jasmine 2.0. The toHaveBeenCalled matcher will return true if the spy was called. The toHaveBeenCalledWith matcher will return true if the argument list matches any of the recorded calls to the spy.

 
describe("A spy", function() {
var foo, bar = null;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    }
  };

  spyOn(foo, 'setBar');

  foo.setBar(123);
  foo.setBar(456, 'another param');
});

it("tracks that the spy was called", function() {
  expect(foo.setBar).toHaveBeenCalled();
});

it("tracks all the arguments of its calls", function() {
  expect(foo.setBar).toHaveBeenCalledWith(123);
  expect(foo.setBar).toHaveBeenCalledWith(456, 'another param');
});

it("stops all execution on a function", function() {
  expect(bar).toBeNull();
});
});

Spies: and.callThrough

By chaining the spy with and.callThrough, the spy will still track all calls to it but in addition it will delegate to the actual implementation.

 
describe("A spy, when configured to call through", function() {
var foo, bar, fetchedBar;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    },
    getBar: function() {
      return bar;
    }
  };

  spyOn(foo, 'getBar').and.callThrough();

  foo.setBar(123);
  fetchedBar = foo.getBar();
});

it("tracks that the spy was called", function() {
  expect(foo.getBar).toHaveBeenCalled();
});

it("should not affect other functions", function() {
  expect(bar).toEqual(123);
});

it("when called returns the requested value", function() {
  expect(fetchedBar).toEqual(123);
});
});

Spies: and.returnValue

By chaining the spy with and.returnValue, all calls to the function will return a specific value.

 
describe("A spy, when configured to fake a return value", function() {
var foo, bar, fetchedBar;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    },
    getBar: function() {
      return bar;
    }
  };

  spyOn(foo, "getBar").and.returnValue(745);

  foo.setBar(123);
  fetchedBar = foo.getBar();
});

it("tracks that the spy was called", function() {
  expect(foo.getBar).toHaveBeenCalled();
});

it("should not affect other functions", function() {
  expect(bar).toEqual(123);
});

it("when called returns the requested value", function() {
  expect(fetchedBar).toEqual(745);
});
});

Spies: and.callFake

By chaining the spy with and.callFake, all calls to the spy will delegate to the supplied function.

 
describe("A spy, when configured with an alternate implementation", function() {
var foo, bar, fetchedBar;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    },
    getBar: function() {
      return bar;
    }
  };

If the function being spied on receives arguments that the fake needs, you can get those as well

 
    spyOn(foo, "getBar").and.callFake(function(arguments, can, be, received) {
    return 1001;
  });

  foo.setBar(123);
  fetchedBar = foo.getBar();
});

it("tracks that the spy was called", function() {
  expect(foo.getBar).toHaveBeenCalled();
});

it("should not affect other functions", function() {
  expect(bar).toEqual(123);
});

it("when called returns the requested value", function() {
  expect(fetchedBar).toEqual(1001);
});
});

Spies: and.throwError

By chaining the spy with and.throwError, all calls to the spy will throw the specified value as an error.

 
describe("A spy, when configured to throw an error", function() {
var foo, bar;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    }
  };

  spyOn(foo, "setBar").and.throwError("quux");
});

it("throws the value", function() {
  expect(function() {
    foo.setBar(123)
  }).toThrowError("quux");
});
});

Spies: and.stub

When a calling strategy is used for a spy, the original stubbing behavior can be returned at any time with and.stub.

 
describe("A spy", function() {
var foo, bar = null;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    }
  };

  spyOn(foo, 'setBar').and.callThrough();
});

it("can call through and then stub in the same spec", function() {
  foo.setBar(123);
  expect(bar).toEqual(123);

  foo.setBar.and.stub();
  bar = null;

  foo.setBar(123);
  expect(bar).toBe(null);
});
});

Other tracking properties

Every call to a spy is tracked and exposed on the calls property.

 
describe("A spy", function() {
var foo, bar = null;

beforeEach(function() {
  foo = {
    setBar: function(value) {
      bar = value;
    }
  };

  spyOn(foo, 'setBar');
});

.calls.any(): returns false if the spy has not been called at all, and then true once at least one call happens.

 
  it("tracks if it was called at all", function() {
  expect(foo.setBar.calls.any()).toEqual(false);

  foo.setBar();

  expect(foo.setBar.calls.any()).toEqual(true);
});

.calls.count(): returns the number of times the spy was called

 
  it("tracks the number of times it was called", function() {
  expect(foo.setBar.calls.count()).toEqual(0);

  foo.setBar();
  foo.setBar();

  expect(foo.setBar.calls.count()).toEqual(2);
});

.calls.argsFor(index): returns the arguments passed to call number index

 
  it("tracks the arguments of each call", function() {
  foo.setBar(123);
  foo.setBar(456, "baz");

  expect(foo.setBar.calls.argsFor(0)).toEqual([123]);
  expect(foo.setBar.calls.argsFor(1)).toEqual([456, "baz"]);
});

.calls.allArgs(): returns the arguments to all calls

 
  it("tracks the arguments of all calls", function() {
  foo.setBar(123);
  foo.setBar(456, "baz");

  expect(foo.setBar.calls.allArgs()).toEqual([[123],[456, "baz"]]);
});

.calls.all(): returns the context (the this) and arguments passed all calls

 
  it("can provide the context and arguments to all calls", function() {
  foo.setBar(123);

  expect(foo.setBar.calls.all()).toEqual([{object: foo, args: [123]}]);
});

.calls.mostRecent(): returns the context (the this) and arguments for the most recent call

 
  it("has a shortcut to the most recent call", function() {
  foo.setBar(123);
  foo.setBar(456, "baz");

  expect(foo.setBar.calls.mostRecent()).toEqual({object: foo, args: [456, "baz"]});
});

.calls.first(): returns the context (the this) and arguments for the first call

 
  it("has a shortcut to the first call", function() {
  foo.setBar(123);
  foo.setBar(456, "baz");

  expect(foo.setBar.calls.first()).toEqual({object: foo, args: [123]});
});

When inspecting the return from all(), mostRecent() and first(), the object property is set to the value of this when the spy was called.

 
  it("tracks the context", function() {
  var spy = jasmine.createSpy('spy');
  var baz = {
    fn: spy
  };
  var quux = {
    fn: spy
  };
  baz.fn(123);
  quux.fn(456);

  expect(spy.calls.first().object).toBe(baz);
  expect(spy.calls.mostRecent().object).toBe(quux);
});

.calls.reset(): clears all tracking for a spy

 
  it("can be reset", function() {
  foo.setBar(123);
  foo.setBar(456, "baz");

  expect(foo.setBar.calls.any()).toBe(true);

  foo.setBar.calls.reset();

  expect(foo.setBar.calls.any()).toBe(false);
});
});

Spies: createSpy

When there is not a function to spy on, jasmine.createSpy can create a "bare" spy. This spy acts as any other spy - tracking calls, arguments, etc. But there is no implementation behind it. Spies are JavaScript objects and can be used as such.

 
describe("A spy, when created manually", function() {
var whatAmI;

beforeEach(function() {
  whatAmI = jasmine.createSpy('whatAmI');

  whatAmI("I", "am", "a", "spy");
});

it("is named, which helps in error reporting", function() {
  expect(whatAmI.and.identity()).toEqual('whatAmI');
});

it("tracks that the spy was called", function() {
  expect(whatAmI).toHaveBeenCalled();
});

it("tracks its number of calls", function() {
  expect(whatAmI.calls.count()).toEqual(1);
});

it("tracks all the arguments of its calls", function() {
  expect(whatAmI).toHaveBeenCalledWith("I", "am", "a", "spy");
});

it("allows access to the most recent call", function() {
  expect(whatAmI.calls.mostRecent().args[0]).toEqual("I");
});
});

Spies: createSpyObj

In order to create a mock with multiple spies, use jasmine.createSpyObj and pass an array of strings. It returns an object that has a property for each string that is a spy.

 
describe("Multiple spies, when created manually", function() {
var tape;

beforeEach(function() {
  tape = jasmine.createSpyObj('tape', ['play', 'pause', 'stop', 'rewind']);

  tape.play();
  tape.pause();
  tape.rewind(0);
});

it("creates spies for each requested function", function() {
  expect(tape.play).toBeDefined();
  expect(tape.pause).toBeDefined();
  expect(tape.stop).toBeDefined();
  expect(tape.rewind).toBeDefined();
});

it("tracks that the spies were called", function() {
  expect(tape.play).toHaveBeenCalled();
  expect(tape.pause).toHaveBeenCalled();
  expect(tape.rewind).toHaveBeenCalled();
  expect(tape.stop).not.toHaveBeenCalled();
});

it("tracks all the arguments of its calls", function() {
  expect(tape.rewind).toHaveBeenCalledWith(0);
});
});

Matching Anything with jasmine.any

jasmine.any takes a constructor or "class" name as an expected value. It returns true if the constructor matches the constructor of the actual value.

 
describe("jasmine.any", function() {
it("matches any value", function() {
  expect({}).toEqual(jasmine.any(Object));
  expect(12).toEqual(jasmine.any(Number));
});

describe("when used with a spy", function() {
  it("is useful for comparing arguments", function() {
    var foo = jasmine.createSpy('foo');
    foo(12, function() {
      return true;
    });

    expect(foo).toHaveBeenCalledWith(jasmine.any(Number), jasmine.any(Function));
  });
});
});

Partial Matching with jasmine.objectContaining

jasmine.objectContaining is for those times when an expectation only cares about certain key/value pairs in the actual.

 
describe("jasmine.objectContaining", function() {
var foo;

beforeEach(function() {
  foo = {
    a: 1,
    b: 2,
    bar: "baz"
  };
});

it("matches objects with the expect key/value pairs", function() {
  expect(foo).toEqual(jasmine.objectContaining({
    bar: "baz"
  }));
  expect(foo).not.toEqual(jasmine.objectContaining({
    c: 37
  }));
});

describe("when used with a spy", function() {
  it("is useful for comparing arguments", function() {
    var callback = jasmine.createSpy('callback');

    callback({
      bar: "baz"
    });

    expect(callback).toHaveBeenCalledWith(jasmine.objectContaining({
      bar: "baz"
    }));
    expect(callback).not.toHaveBeenCalledWith(jasmine.objectContaining({
      c: 37
    }));
  });
});
});

Mocking the JavaScript Timeout Functions

This syntax has changed for Jasmine 2.0. The Jasmine Clock is available for a test suites that need the ability to use setTimeout or setInterval callbacks. It makes the timer callbacks synchronous, executing the registered functions only once the clock is ticked forward in time. This makes timer-related code much easier to test.

 
describe("Manually ticking the Jasmine Clock", function() {
var timerCallback;

It is installed with a call to jasmine.clock().install in a spec or suite that needs to call the timer functions.

 
  beforeEach(function() {
  timerCallback = jasmine.createSpy("timerCallback");
  jasmine.clock().install();
});

Be sure to uninstall the clock after you are done to restore the original timer functions.

 
  afterEach(function() {
  jasmine.clock().uninstall();
});

Calls to any registered callback are triggered when the clock is ticked forward via the jasmine.clock().tick function, which takes a number of milliseconds.

 
  it("causes a timeout to be called synchronously", function() {
  setTimeout(function() {
    timerCallback();
  }, 100);

  expect(timerCallback).not.toHaveBeenCalled();

  jasmine.clock().tick(101);

  expect(timerCallback).toHaveBeenCalled();
});

it("causes an interval to be called synchronously", function() {
  setInterval(function() {
    timerCallback();
  }, 100);

  expect(timerCallback).not.toHaveBeenCalled();

  jasmine.clock().tick(101);
  expect(timerCallback.calls.count()).toEqual(1);

  jasmine.clock().tick(50);
  expect(timerCallback.calls.count()).toEqual(1);

  jasmine.clock().tick(50);
  expect(timerCallback.calls.count()).toEqual(2);
});
});

Asynchronous Support

This syntax has changed for Jasmine 2.0. Jasmine also has support for running specs that require testing asynchronous operations.

 
describe("Asynchronous specs", function() {
var value;

Calls to beforeEach, it, and afterEach can take an optional single argument that should be called when the async work is complete.

 
  beforeEach(function(done) {
  setTimeout(function() {
    value = 0;
    done();
  }, 1);
});

This spec will not start until the done function is called in the call to beforeEach above. And this spec will not complete until its done is called.

 
  it("should support async execution of test preparation and expectations", function(done) {
  value++;
  expect(value).toBeGreaterThan(0);
  done();
});

By default jasmine will wait for 5 seconds for an asynchronous spec to finish before causing a timeout failure. If the timeout expires before done is called, the current spec will be marked as failed and suite execution will continue as if done was called.

If specific specs should fail faster or need more time this can be adjusted by setting jasmine.DEFAULT_TIMEOUT_INTERVAL around them.

If the entire suite should have a different timeout, jasmine.DEFAULT_TIMEOUT_INTERVAL can be set globally, outside of any given describe.

 
  describe("long asynchronous specs", function() {
  var originalTimeout;
  beforeEach(function() {
    originalTimeout = jasmine.DEFAULT_TIMEOUT_INTERVAL;
    jasmine.DEFAULT_TIMEOUT_INTERVAL = 10000;
  });

  it("takes a long time", function(done) {
    setTimeout(function() {
      done();
    }, 9000);
  });

  afterEach(function() {
    jasmine.DEFAULT_TIMEOUT_INTERVAL = originalTimeout;
  });
});
});

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Thanks

Running documentation inspired by @mjackson and the 2012 Fluent Summit.