Stubs, Spies, and Clocks

What you'll learn

• Which libraries Cypress includes to provide typical testing functionality
• How to use stubs for asserting that code was called but preventing it from executing
• How to use spies for asserting that code was called without interfering with its execution
• How to control time for deterministically testing code that is time-dependent
• How Cypress improves and extends the included libraries

Capabilities

Cypress comes built in with the ability to stub and spy with cy.stub(), cy.spy() or modify your application's time with cy.clock() - which lets you manipulate Date, setTimeout, clearTimeout, setInterval, or clearInterval

Libraries and Tools

Cypress automatically bundles and wraps these libraries:

• sinon provides the cy.stub() and cy.spy() APIs
• lolex provides the cy.clock() and cy.tick() APIs
• sinon-chai adds chai assertions for stubs and spies

Common Scenarios

Stubs

// create a standalone stub (generally for use in unit test)
cy.stub()

// replace obj.method() with a stubbed function
cy.stub(obj, 'method')

// force obj.method() to return "foo"
cy.stub(obj, 'method').returns('foo')

// force obj.method() when called with "bar" argument to return "foo"
cy.stub(obj, 'method').withArgs('bar').returns('foo')

// force obj.method() to return a promise which resolves to "foo"
cy.stub(obj, 'method').resolves('foo')

// force obj.method() to return a promise rejected with an error
cy.stub(obj, 'method').rejects(new Error('foo'))

Spies

cy.spy(obj, 'method')

Clock

With cy.clock() you can control:

• Date
• setTimeout
• setInterval

cy.clock()
cy.visit('http://localhost:3333')
cy.get('#search').type('Acme Company')
cy.tick(1000)
// more test code here

// restore the clock
cy.clock().then((clock) => {
  clock.restore()
})
// more test code here