react-native-render-builder

Encapsulate Context/Data Providers when testing Components and Hooks in React-Native

Extension of @testing-library/react-native render and renderHook functions with a builder interface for easily reusing setup of your JSX tree.

Install

yarn

yarn add --dev react-native-render-builder

npm

npm install --save-dev react-native-render-builder

This library has a peerDependencies listing for @testing-library/react-native. Make sure you install it alongside this library.

Usage

First create your RenderBuilder with any builder methods for adding in components you want

import { CounterProvider } from './CounterContext';
import { ReactRenderBuilder } from 'react-native-render-builder';

export class RenderBuilder extends ReactRenderBuilder {
    counter(initialValue: number): this {
        this.addElement(children => <CounterProvider initialValue={initialValue} children={children}/>);
        return this;
    }
}

Then you can use it in your tests

import React from 'react';
import { Text, View } from 'react-native';
import { describe, expect, it } from '@jest/globals';
import { useCounter } from './CounterContext';
import { RenderBuilder } from './RenderBuilder';

describe('hello with counter 1', () => {
    const renderBuilder = new RenderBuilder().counter(1);

    it('render correct string in Hello Component', () => {
        const renderApi = renderBuilder.render(<Hello/>);
        renderApi.getByText('Hello 1');
    });

    it('returns correct string in useHelloHook', () => {
        const helloText = renderBuilder.renderHookResult(useHelloHook);
        expect(helloText).toEqual('Hello 1');
    });
});

function Hello() {
    const counterValue = useHelloHook();
    return (
        <View>
            <Text>{counterValue}</Text>
        </View>
    );
}

function useHelloHook() {
    const counterValue = useCounter();
    return `Hello ${counterValue.value}`;
}

Documentation

ReactRenderBuilder

Wraps @testing-library/react-native render and renderHook functions with a builder interface for easily reusing setup of your JSX tree.

Typically, you will extend this class (as in the example above) and add in builder methods you will use in your tests for reusing JSX Tree setup.

Methods

addElement

Only to be used on your extension of ReactRenderBuilder, this is used in your builder methods for wrapping a component in the tree.

Parameters

• wrapperElement: ProviderFunction that is a function that given a child element returns an Element wrapped with that child.

Example

this.addElement(children => <MyContext children={children}/>);

render

Wraps @testing-library/react-native render function, but wraps given element with tree constructed via addElement in builder methods.

Parameters

• element: React JSX Element to render

Returns

• renderAPI: @testing-library/react-native RenderAPI

Example

const renderAPI = new RenderBuilder().render(<MyComponent/>);

toJSX

Returns JSX Tree that will be passed to render. Useful for debugging or for rerendering via the rerender method from the RenderAPI.

Parameters

• element: React JSX Element to render

Returns

• JSX element that is the entire tree

Example

const jsxTree = new RenderBuilder().toJSX(<MyComponent/>);

renderHook

Wraps @testing-library/react-native renderHook function, but wraps given hook with tree constructed via addElement in builder methods.

Parameters

• hook: React Hook to render

Returns

• renderHookResult: @testing-library/react-native RenderHookResult

Example

const renderHookResult = new RenderBuilder().renderHook(useMyHook);

renderHookResult

Same as renderHook but returns the given hooks return value. Same as calling renderHook(useMyHook).result.current.

Parameters

• hook: React Hook to render

Returns

• return value of given hook

Example

const helloString = new RenderBuilder().renderHookResult(() => useHello('John'));