{"id":1666,"date":"2017-05-30T13:00:00","date_gmt":"2017-05-30T11:00:00","guid":{"rendered":"https:\/\/demo.sidekick.be\/itenium\/javascript-testing-jasmine-spies\/"},"modified":"2025-11-28T13:31:46","modified_gmt":"2025-11-28T12:31:46","slug":"javascript-testing-jasmine-spies","status":"publish","type":"post","link":"https:\/\/demo.sidekick.be\/itenium\/blog\/javascript\/javascript-testing-jasmine-spies\/","title":{"rendered":"JavaScript Testing: Jasmine Spies"},"content":{"rendered":"

spyOn<\/h1>\n
var bar = 0;\nconst foo = {\n  setBar(value, times) {\n    bar = value * (times || 1);\n    return bar;\n  }\n};\n\nbeforeEach(() => {\n  const theSpy = spyOn(foo, 'setBar');\n  expect(theSpy.and.identity()).toBe('setBar');\n\n  foo.setBar(1);\n  foo.setBar(2, 10);\n});\n\nit('can check if called', () => {\n  expect(foo.setBar).toHaveBeenCalled();\n  expect(foo.setBar.calls.any()).toBe(true);\n});\n\nit('how many times', () => {\n  expect(foo.setBar).toHaveBeenCalledTimes(2);\n  expect(foo.setBar.calls.count()).toBe(2);\n});\n\nit('and with which parameters', () => {\n  expect(foo.setBar).toHaveBeenCalledWith(1);\n  expect(foo.setBar).toHaveBeenCalledWith(2, 10);\n});\n\n\/\/ Also:\n\/\/ toHaveBeenCalledBefore(anotherSpy)\n\nit('but does not execute the function', () => {\n  expect(bar).toBe(0);\n});\n<\/code><\/pre>\n
Or create your own spies:<\/p>\n
it('create bare spy without implementation', () => {\n  const spy = jasmine.createSpy().and.returnValue(true);\n  expect(spy()).toBe(true);\n});\n\nit('create spy object with spy functions action1 and action2', () => {\n  const spyObj = jasmine.createSpyObj('id', ['action1', 'action2']);\n  spyObj.action1();\n  expect(spyObj).toHaveSpyInteractions();\n  expect(spyObj.action1).toHaveBeenCalled();\n  expect(spyObj.action2).not.toHaveBeenCalled();\n});\n\nit('create spy object with return values 15 and 18', () => {\n  const spyObj = jasmine.createSpyObj('id', {action1: 15, action2: 18});\n  expect(spyObj.action1()).toBe(15);\n});\n<\/code><\/pre>\n
Spy.and<\/h1>\n
beforeEach(() => {\n  this.foo = foo;\n});\n\nit('can actually execute the function', () => {\n  spyOn(this.foo, 'setBar').and.callThrough();\n  foo.setBar(2, 10);\n  expect(bar).toBe(2 * 10);\n});\n\nit('or do something else', () => {\n  spyOn(this.foo, 'setBar').and.callFake(value => value + 1);\n  const calced = foo.setBar(5);\n  expect(calced).toBe(6);\n});\n\nit('allows returning canned values', () => {\n  spyOn(this.foo, 'setBar').and.returnValue(1);\n  \/\/.and.returnValues('first call result', 'second');\n  const canned = foo.setBar();\n  expect(canned).toBe(1);\n});\n\nit('or just throw an error', () => {\n  spyOn(this.foo, 'setBar').and.throwError('quux');\n  expect(foo.setBar).toThrowError('quux');\n});\n<\/code><\/pre>\n
Spy.calls<\/h1>\n
it('knows about arguments, returnValues and more', () => {\n  const spie = jasmine.createSpy('identity').and.callFake(v => v * 5);\n  spie(1);\n  spie(2, 'arg');\n\n  \/\/ spie.calls.any() and spie.calls.count()\n\n  \/\/ Full callData\n  expect(spie.calls.first()).toBe(spie.calls.all()[0]);\n  expect(spie.calls.mostRecent()).toEqual({\n    object: jasmine.any(Object),\n    args: [2, 'arg'],\n    returnValue: 10,\n    invocationOrder: jasmine.any(Number)\n  });\n\n  \/\/ Just the arguments\n  expect(spie.calls.argsFor(0)).toEqual([1]);\n  expect(spie.calls.allArgs()).toEqual([[1], [2, 'arg']]);\n\n  spie.calls.reset();\n  expect(spie).not.toHaveBeenCalled();\n});\n<\/code><\/pre>\n
spyOnProperty<\/h1>\n
const foop = {\n  get value() {},\n  set value(v) {}\n};\n\nit('can spy on getter', () => {\n  spyOnProperty(foop, 'value', 'get').and.returnValue(1);\n  expect(foop.value).toBe(1);\n});\n\nit('and on setters', () => {\n  const spiez = spyOnProperty(foop, 'value', 'set');\n  foop.value = true;\n  expect(spiez).toHaveBeenCalled();\n});\n<\/code><\/pre>\n
Also in this series<\/h1>\n