spy

Wrap a method in a spy in order to record calls to and arguments of the function.

cy.spy() is a utility function, and is not a Cypress command, query or assertion. It is not retryable, chainable, or timeout-able.

Syntax

cy.spy(object, method)

Usage

Correct Usage

cy.spy(user, 'addFriend')
cy.spy(user, 'addFriend').as('addFriend')

Arguments

object (Object)

The object that has the method to be wrapped.

method (String)

The name of the method on the object to be wrapped.

Yields

• cy.spy() is synchronous and returns a value (the spy) instead of a Promise-like chain-able object. It can be aliased.
• cy.spy() returns a Sinon.js spy. All methods found on Sinon.JS spies are supported.

Examples

Method

Wrap a method with a spy

// assume App.start calls util.addListeners
cy.spy(util, 'addListeners')
App.start()
expect(util.addListeners).to.be.called

Disable logging to Command Log

You can chain a .log(bool) method to disable cy.stub() calls from being shown in the Command Log. This may be useful when your stubs are called an excessive number of times.

const obj = {
  foo() {},
}
const stub = cy.stub(obj, 'foo').log(false)

More cy.spy() examples

Aliases

You can alias spies, similar to how .as() works. This can make your spies easier to identify in error messages and Cypress's command log, and allows you to assert against them later using cy.get().

const obj = {
  foo() {},
}
const spy = cy.spy(obj, 'foo').as('anyArgs')
const withFoo = spy.withArgs('foo').as('withFoo')

obj.foo()

expect(spy).to.be.called
cy.get('@withFoo').should('be.called') // purposefully failing assertion

You will see the following in the command log:

Notes

Restores

Automatic reset/restore between tests

cy.spy() creates spies in a sandbox, so all spies created are automatically reset/restored between tests without you having to explicitly reset/restore them.

Differences

Difference between cy.spy() and cy.stub()

The main difference between cy.spy() and cy.stub() is that cy.spy() does not replace the method, it only wraps it. So, while invocations are recorded, the original method is still called. This can be very useful when testing methods on native browser objects. You can verify a method is being called by your test and still have the original method action invoked.

Assertions

Assertion Support

Cypress has also built-in Sinon-Chai support, so any assertions supported by Sinon-Chai can be used without any configuration.

Command Log

Create a spy, alias it, and call it

const obj = {
  foo() {},
}
const spy = cy.spy(obj, 'foo').as('foo')

obj.foo('foo', 'bar')
expect(spy).to.be.called

The command above will display in the Command Log as:

When clicking on the spy-1 event within the command log, the console outputs the following:

History

See also

• .as()
• cy.clock()
• Guide: Stubs, Spies and Clocks
• Recipe: Stubbing, Spying
• cy.stub()