jest-mock-external-components

Easy automock your external react components

Do you like write component tests? Do you like react-test-renderer more than shallow renderer? Do you feel sometimes that it would be great to combine both shallow renderer and react-test-renderer to prevent rendering inner components? Do you feel headcache when writing tests for something like styled-components ? Are you bored to write numerous jest.mock() calls to mock your component?

If the answer for any of these questions is "Yes" then you come to the right place.

Much often, you want to mock/don't render external components. Almost always these external components are being imported through import statement import A from "./a". And very often you want to full render the inner (helpers or styled) components:

import Button from "./Button";
import AnotherComp from "./AnotherComp";
 
const SomeText = () => <h1>SomeText</h1>
 
const SomeLabel = styled.label`
    font-size: 0.8em;
`;
 
const MyButton = styled(Button)`
    font-size: 2em;
`
 
const Component = () =>
<div>
    <SomeText />
    <AnotherComp />
    <SomeLabel>Label</SomeLabel>
    <MyButton>Button</MyButton>
</div>
 

Here you probably want to fully render SomeText , SomeLabel and partially MyButton (render styles but don't render Button itself). AnotherComp should remain non-rendered (so it's internals won't affect the component test).

This is not achievable by standard react-test-renderer, it will give you snapshot similar to this:

.SomeLabelCss {}
 
.MyButtonCss {}
 
// Shouldn't be here
.ButtonCss {}
 
// Shouldn't be here
.AnotherCompCss {}
 
<div>
    <h1>SomeText</h1>
    // Shouldn't be here
    <div className="AnotherCompCss">AnotherComp internals</div>
    <label className="SomeLabelCss">Label</label>
    // Shouldn't be here
    <button className="MyButtonCss ButtonCss">Button</button>
</div>

Shallow renderer also won't give you desired result:

// No styles since it doesn't unwrap styled-component HOC
 
<div>
    // Didn't unwrap the internal component
    <SomeText />
    <AnotherComp />
    // Didn't unwrap the internal component
    <SomeLabel>Label</SomeLabel>
    // Didn't unwrap the internal component
    <MyButton>Button</MyButton>
</div>
 

Ideally, you want this snapshot:

.SomeLabelCss {}
 
.MyButtonCss {}
 
<div>
    <h1>SomeText></h1>
    // External component shouldn't be rendered
    <AnotherComp />
    <label className="SomeLabelCss">Label</label>
    // Unwrap styled HOC but don't render further. Button already has dedicated test
    <Button className="MyButtonCss">Button</Button>
</div>
 

This is achievable by mocking components using jest.mock() but this is boring and repetetive task, especially when you have to mock many components:

    jest.mock("../AnotherComp", () => "AnotherComp");
    jest.mock("../Button", () => "Button");
    jest.mock("../SomeComp", () => ({ SomeComp: "SomeComp" })); // very ugly for named exports
    // etc...

Finally, now you can just use jest-mock-external-components:

import Component from "../mycomponent";
import { mockExternalComponents } from "jest-mock-external-components";
mockExteralComponents(Component);
// will automatically mock <Button /> and <AnotherComp />
 
// Use react-test-renderer
const t = create(<Component />);
expect(t.toJSON()).toMatchSnapshot();

and it will you give the snapshot which you want with mocked external dependencies and fully-rendered internal components! and it's not shallow, so the lifecycle, refs etc will continue to work.

Installation and setup

yarn add jest-mock-external-components --dev or npm install jest-mock-external-components --save-dev

Add to your .babelrc / .babelrc.js / babel.config.js

    plugins: [
        "jest-mock-external-components/babel",
    ]