Your first suite

Suites: describe Your Tests

The describe function is for grouping related specs, typically each test file has one at the top level. The string parameter is for naming the collection of specs, and will be concatenated with specs to make a spec's full name. This aids in finding specs in a large suite. If you name them well, your specs read as full sentences in traditional BDD style.

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() {
    let 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);
    });

Jasmine has a rich set of matchers included, you can find the full list in the API docs There is also the ability to write custom matchers for when a project's domain calls for specific assertions that are not included in Jasmine.

 
});

Setup and Teardown

To help a test suite DRY up any duplicated setup and teardown code, Jasmine provides the global beforeEach, afterEach, beforeAll, and afterAll functions.

 
describe("A suite with some shared setup", function() {
    let foo = 0;

As the name implies, the beforeEach function is called once before each spec in the describe in which it is called

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

and the afterEach function is called once after each spec.

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

The beforeAll function is called only once before all the specs in describe are run

 
    beforeAll(function() {
        foo = 1;
    });

and the afterAll function is called after all specs finish

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

beforeAll and afterAll can be used to speed up test suites with expensive setup and teardown.

However, be careful using beforeAll and afterAll! Since they are not reset between specs, it is easy to accidentally leak state between your specs so that they erroneously pass or fail.

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.

Note: If you want to use the this keyword to share variables, you must use the function keyword and not arrow functions.

 
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);
    });
});

Manually failing a spec with fail

The fail function causes a spec to fail. It can take a failure message or an Error object as a parameter.

 
describe("A spec using the fail function", function() {
    function foo(x, callBack) {
        if (x) {
            callBack();
        }
    };

    it("should not call the callBack", function() {
        foo(false, function() {
            fail("Callback has been called");
        });
    });
});

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() {
    let 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() {
        let 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 show as pending.

 
xdescribe("A spec", function() {
    let 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. A string passed to pending will be treated as a reason and displayed when the suite finishes.

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

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

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

You can define what the spy will do when invoked with and.

 
        spyOn(foo, 'setBar');

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

The toHaveBeenCalled matcher will pass if the spy was called.

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

The toHaveBeenCalledTimes matcher will pass if the spy was called the specified number of times.

 
    it("tracks that the spy was called x times", function() {
        expect(foo.setBar).toHaveBeenCalledTimes(2);
    });

The toHaveBeenCalledWith matcher will return true if the argument list matches any of the recorded calls to the spy.

 
    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();
    });

You get all of the data that a spy tracks about its calls with calls

 
    it("tracks if it was called at all", function() {
        foo.setBar();

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

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.

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

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

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

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

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() {
    let 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();
    });
});

Matching with more finesse

Sometimes you don't want to match with exact equality. Jasmine provides a number of asymmetric equality testers.

 
describe("Matching with finesse", function() {

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() {
                const foo = jasmine.createSpy('foo');
                foo(12, function() {
                    return true;
                });
    
                expect(foo).toHaveBeenCalledWith(jasmine.any(Number), jasmine.any(Function));
            });
        });
    });

jasmine.anything returns true if the actual value is not null or undefined.

 
    describe("jasmine.anything", function() {
        it("matches anything", function() {
            expect(1).toEqual(jasmine.anything());
        });

        describe("when used with a spy", function() {
            it("is useful when the argument can be ignored", function() {
                const foo = jasmine.createSpy('foo');
                foo(12, function() {
                    return false;
                });

                expect(foo).toHaveBeenCalledWith(12, jasmine.anything());
            });
        });
    });

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

 
    describe("jasmine.objectContaining", function() {
        let 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() {
                const callback = jasmine.createSpy('callback');

                callback({
                    bar: "baz"
                });

                expect(callback).toHaveBeenCalledWith(jasmine.objectContaining({
                    bar: "baz"
                }));
            });
        });
    });

jasmine.arrayContaining is for those times when an expectation only cares about some of the values in an array.

 
    describe("jasmine.arrayContaining", function() {
        let foo;

        beforeEach(function() {
            foo = [1, 2, 3, 4];
        });

        it("matches arrays with some of the values", function() {
            expect(foo).toEqual(jasmine.arrayContaining([3, 1]));
            expect(foo).not.toEqual(jasmine.arrayContaining([6]));
        });

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

                callback([1, 2, 3, 4]);

                expect(callback).toHaveBeenCalledWith(jasmine.arrayContaining([4, 2, 3]));
                expect(callback).not.toHaveBeenCalledWith(jasmine.arrayContaining([5, 2]));
            });
        });
    });

jasmine.stringMatching is for when you don't want to match a string in a larger object exactly, or match a portion of a string in a spy expectation.

 
    describe('jasmine.stringMatching', function() {
        it("matches as a regexp", function() {
            expect({foo: 'bar'}).toEqual({foo: jasmine.stringMatching(/^bar$/)});
            expect({foo: 'foobarbaz'}).toEqual({foo: jasmine.stringMatching('bar')});
        });

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

                callback('foobarbaz');

                expect(callback).toHaveBeenCalledWith(jasmine.stringMatching('bar'));
                expect(callback).not.toHaveBeenCalledWith(jasmine.stringMatching(/^bar$/));
            });
        });
    });

Custom asymmetric equality tester

When you need to check that something meets a certain criteria, without being strictly equal, you can also specify a custom asymmetric equality tester simply by providing an object that has an asymmetricMatch function.

 
    describe("custom asymmetry", function() {
        const tester = {
            asymmetricMatch: function(actual) {
                const secondValue = actual.split(',')[1];
                return secondValue === 'bar';
            }
        };

        it("dives in deep", function() {
            expect("foo,bar,baz,quux").toEqual(tester);
        });

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

                callback('foo,bar,baz');

                expect(callback).toHaveBeenCalledWith(tester);
            });
        });
    });
});

Jasmine Clock

The Jasmine Clock is available for testing time dependent code.

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

It is installed with a call to jasmine.clock().install in a spec or suite that needs to manipulate time.

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

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

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

Mocking the JavaScript Timeout Functions

You can make setTimeout or setInterval synchronous executing the registered functions only once the clock is ticked forward in time.

To execute registered functions, move time 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);
    });

Mocking the Date

The Jasmine Clock can also be used to mock the current date.

 
    describe("Mocking the Date object", function(){
        it("mocks the Date object and sets it to a given time", function() {
            const baseTime = new Date(2013, 9, 23);

If you do not provide a base time to mockDate it will use the current date.

 
            jasmine.clock().mockDate(baseTime);

            jasmine.clock().tick(50);
            expect(new Date().getTime()).toEqual(baseTime.getTime() + 50);
        });
    });
});

Asynchronous Support

Jasmine also has support for running specs that require testing asynchronous operations. The functions that you pass to beforeAll, afterAll, beforeEach, afterEach, and it can be declared async.

Jasmine also supports asynchronous functions that explicitly return promises or that take a callback. See the Asynchronous Work tutorial for more information.

 
describe("Using async/await", function() {
    beforeEach(async function() {
        await soon();
        value = 0;
    });

This spec will not start until the promise returned from the call to beforeEach above is settled. And this spec will not complete until the promise that it returns is settled.

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

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 passing a timeout value to it, etc.

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() {
    beforeEach(async function() {
        await somethingSlow();
    }, 1000);

    it("takes a long time", function() {
        await somethingReallySlow();
    }, 10000);

    afterEach(function() {
        await somethingSlow();
        }, 1000);
    });

    function soon() {
        return new Promise(function(resolve, reject) {
            setTimeout(function() {
                resolve();
            }, 1);
        });
    }
});