`ReactTestUtils` makes it easy to test React components in the testing framework of your choice. At Facebook we use [Jest](https://facebook.github.io/jest/) for painless JavaScript testing. Learn how to get started with Jest through the Jest website's [React Tutorial](http://facebook.github.io/jest/docs/en/tutorial-react.html#content).
> Airbnb has released a testing utility called Enzyme, which makes it easy to assert, manipulate, and traverse your React Components' output. If you're deciding on a unit testing utility to use together with Jest, or any other test runner, it's worth checking out: [http://airbnb.io/enzyme/](http://airbnb.io/enzyme/)
When writing unit tests for React, shallow rendering can be helpful. Shallow rendering lets you render a component "one level deep" and assert facts about what its render method returns, without worrying about the behavior of child components, which are not instantiated or rendered. This does not require a DOM.
> You will have to provide any event property that you're using in your component (e.g. keyCode, which, etc...) as React is not creating any of these for you.
> You will need to have `window`, `window.document` and `window.document.createElement` globally available **before** you import `React`. Otherwise React will think it can't access the DOM and methods like `setState` won't work.
* * *
### `mockComponent()`
```javascript
mockComponent(
componentClass,
[mockTagName]
)
```
Pass a mocked component module to this method to augment it with useful methods that allow it to be used as a dummy React component. Instead of rendering as usual, the component will become a simple `<div>` (or other tag if `mockTagName` is provided) containing any provided children.
> `mockComponent()` is a legacy API. We recommend using [shallow rendering](/docs/test-utils.html#shallow-rendering) or [`jest.mock()`](https://facebook.github.io/jest/docs/en/tutorial-react-native.html#mock-native-modules-using-jestmock) instead.
Returns `true` if `element` is a React element whose type is of a React `componentClass`.
* * *
### `isDOMComponent()`
```javascript
isDOMComponent(instance)
```
Returns `true` if `instance` is a DOM component (such as a `<div>` or `<span>`).
* * *
### `isCompositeComponent()`
```javascript
isCompositeComponent(instance)
```
Returns `true` if `instance` is a user-defined component, such as a class or a function.
* * *
### `isCompositeComponentWithType()`
```javascript
isCompositeComponentWithType(
instance,
componentClass
)
```
Returns `true` if `instance` is a component whose type is of a React `componentClass`.
* * *
### `findAllInRenderedTree()`
```javascript
findAllInRenderedTree(
tree,
test
)
```
Traverse all components in `tree` and accumulate all components where `test(component)` is `true`. This is not that useful on its own, but it's used as a primitive for other test utils.
* * *
### `scryRenderedDOMComponentsWithClass()`
```javascript
scryRenderedDOMComponentsWithClass(
tree,
className
)
```
Finds all DOM elements of components in the rendered tree that are DOM components with the class name matching `className`.
* * *
### `findRenderedDOMComponentWithClass()`
```javascript
findRenderedDOMComponentWithClass(
tree,
className
)
```
Like [`scryRenderedDOMComponentsWithClass()`](#scryrendereddomcomponentswithclass) but expects there to be one result, and returns that one result, or throws exception if there is any other number of matches besides one.
* * *
### `scryRenderedDOMComponentsWithTag()`
```javascript
scryRenderedDOMComponentsWithTag(
tree,
tagName
)
```
Finds all DOM elements of components in the rendered tree that are DOM components with the tag name matching `tagName`.
* * *
### `findRenderedDOMComponentWithTag()`
```javascript
findRenderedDOMComponentWithTag(
tree,
tagName
)
```
Like [`scryRenderedDOMComponentsWithTag()`](#scryrendereddomcomponentswithtag) but expects there to be one result, and returns that one result, or throws exception if there is any other number of matches besides one.
* * *
### `scryRenderedComponentsWithType()`
```javascript
scryRenderedComponentsWithType(
tree,
componentClass
)
```
Finds all instances of components with type equal to `componentClass`.
* * *
### `findRenderedComponentWithType()`
```javascript
findRenderedComponentWithType(
tree,
componentClass
)
```
Same as [`scryRenderedComponentsWithType()`](#scryrenderedcomponentswithtype) but expects there to be one result and returns that one result, or throws exception if there is any other number of matches besides one.
