Create type safe mock React components to use in tests

Check out the jest matcher as well.

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Installation

With npm

npm i -D react-mock-component

or with yarn

yarn add -D react-mock-component

Usage

import React from 'react';
import createReactMock from 'react-mock-component';
import { render } from 'react-dom';

const Foo = createReactMock<{ bar: number }>();
Foo.withProps({ bar: 42 }).renders(<span>fake content</span>);

render(<Foo bar={42} />);

console.log(Foo.renderedWith({ bar: 42 })); // true
console.log(document.body.innerHTML); // <span>fake content</span>

You can of course use this library without TypeScript, you just won't get any errors if you for instance check for the wrong prop.

Type safety

All the methods are fully typed to prevent mistakes where the tests don't match the code they're testing. Moreover, an IDE with good support for TypeScript e.g. WebStorm can provide autocomplete and automatic refactoring of props across code and tests.

API

createReactMock<Props>()

Returns a real component that records the props it receives and allows you to set expectations beforehand or check them afterwards.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render } from 'react-dom';

const Mock = createReactMock<{ foo: string }>();
render(<Mock foo="bar" />);
render(<Mock foo={23} />); // type error

withProps(props: DeepPartial<Props>)

Sets an expectation that the component will receive the given props. Chain it with renders to finish the expectation.

import createReactMock from 'react-mock-component';

const Mock = createReactMock<{ foo: string }>();
Mock.withProps({ foo: 'bar' })
Mock.withProps({ foo: 23 }) // type error
Mock.withProps({ }) // expects any props

An expectation can only be met once, and after the component receives matching props the corresponding expectation will be unset.

If the component receives props that don't match any expectation (either because one wasn't set or because all have been consumed) then it will render null.

renders(jsx: JSX)

Finishes the previously set expectation and sets what the component will render when given the expected props.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render } from 'react-dom';

const Mock = createReactMock<{ foo: string }>();
Mock.withProps({ foo: 'bar' }).renders(<span>foobar</span>);

render(<Mock foo="something else" />); // will render null
render(<Mock foo="bar" />); // will render "foobar"
render(<Mock foo="bar" />); // will render null

renderedWith(props: DeepPartial<Props>): boolean

Check if the component was rendered with the given props.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render } from 'react-dom';

const Mock = createReactMock<{ foo: string }>();
Mock.withProps({ foo: 'bar' }).renders(<span>foobar</span>);

render(<Mock foo="bar" />); // will render "foobar"
render(<Mock foo="baz" />); // will render null

Mock.renderedWith({ foo: "bar" }) // true
Mock.renderedWith({ foo: "baz" }) // true
Mock.renderedWith({ foo: "unexpected" }) // false
Mock.renderedWith({ foo: 23 }) // type error

rendered: boolean

Returns if the component was rendered at least once. The mock doesn't have to have any expectation for this to become true.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render } from 'react-dom';

const Mock1 = createReactMock<{ foo: string }>();
const Mock2 = createReactMock<{ foo: string }>();

render(<Mock1 foo="bar" />); // will render null
Mock1.rendered // true


Mock2.withProps({ foo: 'baz' }).renders(<span>foobar</span>);
render(<Mock2 foo="baz" />); // will render "foobar"
Mock2.rendered // true

mounted: boolean

Returns if the component is currently mounted.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render, unmount } from 'react-dom';

const Mock = createReactMock();

console.log(Mock.mounted); // false
render(<Mock />); 
console.log(Mock.mounted); // true
unmount();
console.log(Mock.mounted); // false

The flag will be cleared when resetting the mock, even if the component is still mounted.

renderCalls: Props[]

Get all the props for all the renders of the mock.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render } from 'react-dom';

const Mock = createReactMock<{ foo: string }>();

render(<Mock foo="bar" />); // will render null
render(<Mock foo="baz" />); // will render null

Mock.renderedCalls[0] // { foo: 'bar' }
Mock.renderedCalls[1] // { foo: 'baz' }

lastProps: Props

Get the props for the last render.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render } from 'react-dom';

const Mock = createReactMock<{ foo: string }>();

render(<Mock foo="bar" />); // will render null
render(<Mock foo="baz" />); // will render null

Mock.lastProps // { foo: 'baz' }

reset()

Clears the render history.

import createReactMock from 'react-mock-component';
import React from 'react';
import { render, unmount } from 'react-dom';

const Mock = createReactMock();
render(<Mock />);

Mock.reset();

console.log(Mock.mounted); // false
console.log(Mock.rendered); // false
console.log(Mock.lastProps); // throws an error

resetAll()

Clears the render history for all created mocks. You can call this in your global test setup.

import { resetAll } from 'react-mock-component';

beforeEach(() => {
  resetAll();
});