{"id":1669,"date":"2017-05-30T10:00:00","date_gmt":"2017-05-30T08:00:00","guid":{"rendered":"https:\/\/demo.sidekick.be\/itenium\/javascript-testing-jasmine-syntax\/"},"modified":"2025-11-28T13:31:46","modified_gmt":"2025-11-28T12:31:46","slug":"javascript-testing-jasmine-syntax","status":"publish","type":"post","link":"https:\/\/demo.sidekick.be\/itenium\/blog\/javascript\/javascript-testing-jasmine-syntax\/","title":{"rendered":"JavaScript Testing: Jasmine syntax"},"content":{"rendered":"

Basic example<\/h1>\n

Time to start writing some real tests with Jasmine!<\/p>\n

describe('basic example', () => {\n  beforeEach(() => {\n    this.result = 1;\n  });\n\n  it('can hardly fail', () => {\n    \/\/ toBe() uses ===\n    expect(this.result).toBe(1);\n\n    \/\/ For primitive types, toEqual\n    \/\/ behaves the same way as toBe\n    \/\/ toEqual goes further however\n    \/\/ by deeply comparing objects.\n    expect({a: {}}).toEqual({a: {}});\n    expect([0, {a: 1}]).toEqual([0, {a: 1}]);\n  });\n\n  afterAll(() => {});\n});\n<\/code><\/pre>\n
A describe<\/code> groups one or more related tests together in a suite. Describes can be nested indefinitely and contain one it<\/code> for each test in the suite.<\/p>\n
beforeAll<\/code> and afterAll<\/code> runs once before\/after all tests in the containing describe are executed. beforeEach<\/code> and afterEach<\/code> runs once before\/after each test is executed.<\/p>\n
The this<\/code> context is shared in the beforeX\/afterX functions and the it<\/code>s, allowing you to setup\/teardown stuff and access them in your tests.<\/p>\n
Matchers<\/h1>\n
Set expectations with matchers. Usage and differences of toBe<\/code> and toEqual<\/code> are already covered in the basic example above. These are the other matchers:<\/p>\n
it('can negate any matcher with .not', () => {\n  expect(1).not.toBe(0);\n});\n\nit('knows about regexes', () => {\n  expect('some bar').toMatch(\/bar$\/);\n  expect('some bar').toMatch('\\sbar');\n});\n\nit('can check numbers', () => {\n  expect(5).toBeLessThan(10); \/\/ .toBeLessThanOrEqual(5);\n  expect(5).toBeGreaterThan(1); \/\/ .toBeGreaterThanOrEqual(5);\n\n  const precision = 3;\n  expect(Math.PI).toBeCloseTo(3.142, precision);\n});\n\nit('has some special matchers', () => {\n  expect(1).toBeTruthy();\n  expect('').toBeFalsy();\n  expect().toBeUndefined();\n  \/\/ .toBeNull(); .toBeDefined(); .toBeNaN();\n  \/\/ .toBeNegativeInfinity(); .toBePositiveInfinity();\n  \/\/ .toHaveClass(domEl): contains the class\n  \/\/ .withContext('show this on failure');\n  \n\nit('gets funky with partial matchers', () => {\n  expect(['a', {b: {}}]).toContain({b: {}});\n  expect('some string').toContain('some');\n\n  expect({bar: 'baz', ack: 'yaye'}).toEqual(jasmine.objectContaining({bar: 'baz'}));\n  expect([1, 2, 3]).not.toEqual(jasmine.arrayContaining([1, 6]));\n  expect({foo: 'foobarbaz'}).toEqual({foo: jasmine.stringMatching('baz$')});\n\n  \/\/ jasmine.arrayWithExactContents()\n  \/\/ .empty(); .notEmpty();\n  \/\/ .truthy(); .falsy();\n});\n\nit('can check for errors', () => {\n  const foo = () => {\n    throw new TypeError('foo bar baz');\n  };\n\n  expect(foo).toThrow();\n\n  \/\/ Error message must be exact match in order to pass\n  expect(foo).toThrowError('foo bar baz');\n  expect(foo).toThrowError(\/bar\/);\n  expect(foo).toThrowError(TypeError);\n  expect(foo).toThrowError(TypeError, 'foo bar baz');\n\n  expect(foo).toThrowMatching(err => err.message.includes('baz'));\n});\n\nit('jasmine.any', () => {\n  expect({}).toEqual(jasmine.any(Object));\n  \/\/ Number, Boolean, Date, String, Array\n  \/\/ Or 'YourType'\n});\n\nit('jasmine.anything', () => {\n  expect(1).toEqual(jasmine.anything());\n});\n<\/code><\/pre>\n
The matchers source<\/a> for if you\u2019d like to take a peek at the implementations.<\/p>\n
Workflow<\/h1>\n
If you are iterating over the same test(s) you can temporarily run these tests by prefixing one or more describe<\/code> and\/or it<\/code>s with an f. You can also execute a single file from the CLI jasmine src\/someSpec.js<\/code>.<\/p>\n
Obviously you\u2019ll never want to do the opposite: exclude a test from the suite. But.. If you must, it is possible to temporarily disable a describe\/it by prefixing it with an x.<\/p>\n
\/\/ f = focused\nfdescribe('only my its will run', () => {\n  it('which is me', () => {});\n  it('and me', () => {});\n  xit('but not me', () => {});\n});\n\nxit('I will not run, even if the fdescribe above is removed', () => {});\n<\/code><\/pre>\n
Other helpers available in an it<\/code>:<\/p>\n