# Cypress Documentation
# Source: https://raw.githubusercontent.com/cypress-io/cypress-documentation/main/docs/api/commands/spy.mdx
# Path: docs/api/commands/spy.mdx

---
title: 'spy | Cypress Documentation'
description: Wrap a method in a spy in order to record calls to and arguments of the function in Cypress.
sidebar_label: spy
---

<ProductHeading product="app" />

# 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.

:::info

**Note:** `.spy()` assumes you are already familiar with our guide:
[Stubs, Spies, and Clocks](/app/guides/stubs-spies-and-clocks)

:::

## Syntax

```javascript
cy.spy(object, method)
```

### Usage

<Icon name="check-circle" color="green" /> **Correct Usage**

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

### Arguments

<Icon name="angle-right" /> **object _(Object)_**

The `object` that has the `method` to be wrapped.

<Icon name="angle-right" /> **method _(String)_**

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

<HeaderYields />

- `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](https://sinonjs.org/releases/v8/spies/). All methods found
  on Sinon.JS spies are supported.

## Examples

### Method

#### Wrap a method with a spy

```javascript
// 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.spy()` calls from being
shown in the Command Log. This may be useful when your stubs are called an
excessive number of times.

```javascript
const obj = {
  foo() {},
}
const spy = cy.spy(obj, 'foo').log(false)
```

#### More `cy.spy()` examples

:::info

[Check out our example recipe testing spying, stubbing and time](/app/references/recipes#Stubbing-and-spying)

:::

### Aliases

You can alias spies, similar to how [`.as()`](/api/commands/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()`.

```javascript
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:

<DocsImage
  src="/img/api/spy/using-spy-with-alias.png"
  alt="spies with aliases"
/>

## Notes

### Restores

#### Automatic reset/restore between tests

`cy.spy()` creates spies in a
[sandbox](https://sinonjs.org/releases/v8/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()`](/api/commands/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](/app/references/bundled-libraries#Sinon-Chai) support, so any
[assertions supported by `Sinon-Chai`](/app/references/assertions#Sinon-Chai)
can be used without any configuration.

## Command Log

**_Create a spy, alias it, and call it_**

```javascript
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:

<DocsImage
  src="/img/api/spy/spying-shows-any-aliases-and-also-any-assertions-made.png"
  alt="Command Log spy"
/>

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

<DocsImage
  src="/img/api/spy/console-shows-spy-arguments-calls-and-the-object-being-spied.png"
  alt="Console Log spy"
/>

## History

| Version                                    | Changes                   |
| ------------------------------------------ | ------------------------- |
| [0.20.0](/app/references/changelog#0-20-0) | Added `.log(bool)` method |
| [0.18.8](/app/references/changelog#0-18-8) | `cy.spy()` command added  |

## See also

- [`.as()`](/api/commands/as)
- [`cy.clock()`](/api/commands/clock)
- [Guide: Stubs, Spies and Clocks](/app/guides/stubs-spies-and-clocks)
- [Recipe: Stubbing, Spying](/app/references/recipes#Stubbing-and-spying)
- [`cy.stub()`](/api/commands/stub)