jasmine-core

Writing Test Suites

This feature allows you to group related specs (tests) together. The 'describe' function is for grouping, and 'it' is for individual specs.

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

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

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

Matchers

Matchers are used to implement a boolean comparison between the actual value and the expected value. The 'toBe' matcher is one of the simplest matchers.

describe('The 'toBe' matcher compares with ===', function() {
  it('and has a positive case', function() {
    expect(true).toBe(true);
  });

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

Setup and Teardown

Setup and teardown functions like 'beforeEach' and 'afterEach' are used to perform actions before and after each spec in a suite, respectively.

describe('A spec', function() {
  beforeEach(function() {
    this.value = 0;
  });

  afterEach(function() {
    this.value = null;
  });

  it('can use the `this` to share state', function() {
    expect(this.value).toEqual(0);
    this.value += 1;
  });

  it('prevents test pollution by having an isolated `this` per spec', function() {
    expect(this.value).toEqual(0);
  });
});

Spies

Spies are used to track calls to functions and all arguments of those calls. They can be used to stub any function and track its usage and calls.

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();
  });
});

Asynchronous Support

Jasmine supports asynchronous testing by using the 'done' function to signal that an async function has completed before moving on to the next spec.

describe('Async spec', function() {
  var value;

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

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