some basic test cases for a React Native Text Input Component using Jest

// TextInputComponent.js

import React, { useState } from 'react';
import { TextInput, View, Button, Text } from 'react-native';

const MyTextInput = () => {
  const [text, setText] = useState('');

  const handleInputChange = (inputText) => {
    setText(inputText);
  };

  const handleButtonPress = () => {
    // Perform some action with the input text
    console.log(`Input Text: ${text}`);
  };

  return (
    <View>
      <TextInput
        placeholder="Type something..."
        value={text}
        onChangeText={handleInputChange}
      />
      <Button title="Submit" onPress={handleButtonPress} />
    </View>
  );
};

export default MyTextInput;

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
  it('handles input change', () => {
    // Render the MyTextInput component
    const { getByPlaceholderText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');

    // Simulate entering text into the input
    fireEvent.changeText(input, 'Hello, World!');

    // Assert that the input value reflects the entered text
    expect(input.props.value).toBe('Hello, World!');
  });
});

Explanation:

1. Render the Component:

   • const { getByPlaceholderText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText function from the returned object.

2. Get the Input Element:

   • const input = getByPlaceholderText('Type something...');: Using getByPlaceholderText to get the input element by its placeholder text.

3. Simulate Entering Text:

   • fireEvent.changeText(input, 'Hello, World!');: Simulating entering the text 'Hello, World!' into the input.

4. Assertion:

   • expect(input.props.value).toBe('Hello, World!');: Asserting that the value prop of the input reflects the entered text. This ensures that the MyTextInput component correctly handles and retains the entered input.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
  it('executes button press', () => {
    // Render the MyTextInput component
    const { getByPlaceholderText, getByText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');
    const button = getByText('Submit');

    // Simulate entering text into the input
    fireEvent.changeText(input, 'Hello, World!');

    // Simulate pressing the submit button
    fireEvent.press(button);

  });
});

Explanation:

1. Render the Component:

   • const { getByPlaceholderText, getByText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText and getByText functions from the returned object.

2. Get Elements:

   • const input = getByPlaceholderText('Type something...');: Using getByPlaceholderText to get the input element by its placeholder text.
   • const button = getByText('Submit');: Using getByText to get the button element by its text content.

3. Simulate Entering Text:

   • fireEvent.changeText(input, 'Hello, World!');: Simulating entering the text 'Hello, World!' into the input.

4. Simulate Button Press:

   • fireEvent.press(button);: Simulating pressing the submit button
   •  

// TextInputComponent.test.js
import React from 'react';
import { render } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
  it('renders with default empty value', () => {
    // Render the MyTextInput component
    const { getByPlaceholderText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');

    // Assert that the input value is an empty string by default
    expect(input.props.value).toBe('');
  });
});

Explanation:

1. Render the Component:

   • const { getByPlaceholderText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText function from the returned object.

2. Get the Input Element:

   • const input = getByPlaceholderText('Type something...');: Using getByPlaceholderText to get the input element by its placeholder text.

3. Assertion:

   • expect(input.props.value).toBe('');: Asserting that the value prop of the input is an empty string by default. This ensures that the component is initially rendered with an empty input value.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
  it('handles empty input correctly', () => {
    // Render the MyTextInput component
    const { getByPlaceholderText, getByText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');
    const button = getByText('Submit');

    // Simulate a button press without entering any text
    fireEvent.press(button);

    // Assertions to check how the component handles empty input
    // Example assertions (customize based on your component's behavior):
    // 1. Check if an error message is displayed
    //    const errorMessage = getByText('Please enter something.');
    //    expect(errorMessage).toBeTruthy();

    // 2. Check if a specific callback function is not called
    //    const mockCallback = jest.fn();
    //    expect(mockCallback).not.toHaveBeenCalled();
  });
});

Explanation:

1. Render the Component:

   • const { getByPlaceholderText, getByText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText and getByText functions from the returned object.

2. Get Elements:

   • const input = getByPlaceholderText('Type something...');: Using getByPlaceholderText to get the input element by its placeholder text.
   • const button = getByText('Submit');: Using getByText to get the button element by its text content.

3. Simulate Button Press:

   • fireEvent.press(button);: Simulating a button press without entering any text into the input.

4. Assertions:

   • Add your specific assertions based on the behavior you expect when handling empty input. In the example, I've included two scenarios:
     • Checking if an error message is displayed when no text is entered.
     • Checking if a specific callback function is not called.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
  it('handles input with special characters', () => {
    const { getByPlaceholderText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');
    fireEvent.changeText(input, 'Special!@#$%^&*()_+-={}[]|:;"<>,.?/~`');
    expect(input.props.value).toBe('Special!@#$%^&*()_+-={}[]|:;"<>,.?/~`');
  });
});

Explanation:

1. Render the Component:

   • const { getByPlaceholderText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText function from the returned object.

2. Get the Input Element:

   • const input = getByPlaceholderText('Type something...');: Using getByPlaceholderText to get the input element by its placeholder text.

3. Simulate Entering Special Characters:

   • fireEvent.changeText(input, 'Special!@#$%^&*()_+-={}[]|:;"<>,.?/~');: Simulating entering a string with various special characters into the input using fireEvent.changeText`.

4. Assertion:

   • expect(input.props.value).toBe('Special!@#$%^&*()_+-={}[]|:;"<>,.?/~');: Asserting that the valueprop of the input reflects the entered string with special characters. This checks whether theMyTextInput` component correctly handles and retains input with special characters.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
 it('renders without crashing', () => {
  // Render the component
  const { getByPlaceholderText, getByText } = render(<MyTextInput />);

  // Get the input element by its placeholder text
  const input = getByPlaceholderText('Type something...');

  // Get the button element by its text content
  const button = getByText('Submit');

  // Assertions to check if the component renders without crashing
  expect(input).toBeInTheDocument();
  expect(button).toBeInTheDocument();
  expect(input).toBeVisible();
  expect(button).toBeVisible();
});
});

Explanation:

1. Render the Component:

   • const { getByPlaceholderText, getByText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText and getByText functions from the returned object.

2. Get Elements:

   • const input = getByPlaceholderText('Type something...');: Using getByPlaceholderText to get the input element by its placeholder text.
   • const button = getByText('Submit');: Using getByText to get the button element by its text content.

3. Assertions:

   • expect(input).toBeInTheDocument();: Asserting that the input element is in the document.
   • expect(button).toBeInTheDocument();: Asserting that the button element is in the document.
   • expect(input).toBeVisible();: Asserting that the input element is visible.
   • expect(button).toBeVisible();: Asserting that the button element is visible.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
  it('displays an error message for invalid input', () => {
    const { getByPlaceholderText, getByText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');
    const button = getByText('Submit');
    fireEvent.changeText(input, 'Invalid Input');
    fireEvent.press(button);
  });
});

Test Logic:

• const errorMessage = getByText('Invalid input. Please try again.');: Using the getByText function to get the element that should contain the error message. Adjust the text content based on what your actual error message is.

• expect(errorMessage).toBeTruthy();: Asserting that the errorMessage element exists and is truthy. If the error message element is found, the test will pass; otherwise, it will fail.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
 it('renders the submit button', () => {
    const { getByText } = render(<MyTextInput />);
    const button = getByText('Submit');
    expect(button).toBeTruthy();
  });
});

Test Logic:

• const { getByText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByText function from the returned object. This function allows you to select elements based on their text content.

• const button = getByText('Submit');: Using the getByText function to get the button element with the text content 'Submit'.

• expect(button).toBeTruthy();: Asserting that the button element exists and is truthy. If the button element is found, the test will pass; otherwise, it will fail.

// TextInputComponent.test.js
import React from 'react';
import { render, fireEvent } from '@testing-library/react-native';
import MyTextInput from './TextInputComponent';

describe('MyTextInput component', () => {
 it('handles input with numbers', () => {
    const { getByPlaceholderText } = render(<MyTextInput />);
    const input = getByPlaceholderText('Type something...');
    fireEvent.changeText(input, '12345');
    expect(input.props.value).toBe('12345');
  });
});

Test Logic:

• const { getByPlaceholderText } = render(<MyTextInput />);: Rendering the MyTextInput component and destructuring the getByPlaceholderText function from the returned object. This function allows you to select elements based on their placeholder text.

• const input = getByPlaceholderText('Type something...');: Using the getByPlaceholderText function to get the input element with the placeholder text 'Type something...'.

• fireEvent.changeText(input, '12345');: Simulating a change in the input text by firing the changeText event with a string that includes numbers.

• expect(input.props.value).toBe('12345');: Asserting that the value prop of the input reflects the text with numbers. This checks whether the MyTextInput component correctly handles and retains the input with numbers.