App.test.tsx

import * as React from 'react';
import {fireEvent, render, waitFor} from '@testing-library/react-native';
import App from '../App';
import testIdConstant from '../testId.constant';
import Snackbar from 'react-native-snackbar';
import MockAdapter from 'axios-mock-adapter';
import axios from 'axios';

jest.mock('react-native-snackbar');
const mock = new MockAdapter(axios);
beforeEach(() => {
  mock.reset();
});

describe('Login Screen', () => {
  it('should display an error message when the input is empty', async () => {
    const {getByTestId, queryByText, getByText} = render(<App />);
    const emailInput = getByTestId(testIdConstant.emailInput);
    const passInput = getByTestId(testIdConstant.passwordInput);
    const btnLogin = getByTestId(testIdConstant.loginBtn);

    fireEvent.changeText(emailInput, '');
    fireEvent.changeText(passInput, '');

    fireEvent.press(btnLogin);

    expect(getByText('Please enter Email')).toBeTruthy();
    expect(getByText('Please enter Password')).toBeTruthy();
  });

  it('should display an error message when the email is invalid', async () => {
    const {getByTestId, queryByText, getByText} = render(<App />);
    const emailInput = getByTestId(testIdConstant.emailInput);
    const btnLogin = getByTestId(testIdConstant.loginBtn);

    fireEvent.changeText(emailInput, 'invalidemail');

    fireEvent.press(btnLogin);

    expect(getByText('Please enter valid Email')).toBeTruthy();
  });

  it('should login with correct credentials', async () => {
    const {getByTestId, queryByText, getByText} = render(<App />);
    const emailInput = getByTestId(testIdConstant.emailInput);
    const passInput = getByTestId(testIdConstant.passwordInput);
    const btnLogin = getByTestId(testIdConstant.loginBtn);

    fireEvent.changeText(emailInput, 'satyam@yopmail.com');
    fireEvent.changeText(passInput, '123456');

    fireEvent.press(btnLogin);
    expect(Snackbar.show).toHaveBeenCalledWith({
      text: 'Success',
      duration: Snackbar.LENGTH_SHORT,
      backgroundColor: '#000',
      marginBottom: 10,
    });
  });
});