Expect

    Harness uses Vitest's expect function for making assertions in your tests. The API is 100% compatible with Vitest's expect functionality.

    Basic Usage

    import { describe, test, expect } from 'react-native-harness';

describe('basic assertions', () => {
  test('primitive values', () => {
    expect(2 + 2).toBe(4);
    expect('hello').toBe('hello');
    expect(true).toBeTruthy();
    expect(false).toBeFalsy();
  });

  test('objects and arrays', () => {
    expect({ name: 'John', age: 30 }).toEqual({ name: 'John', age: 30 });
    expect([1, 2, 3]).toContain(2);
    expect(['apple', 'banana']).toHaveLength(2);
  });

  test('strings and numbers', () => {
    expect('hello world').toContain('world');
    expect('hello world').toMatch(/world/);
    expect(3.14).toBeCloseTo(3.1, 1);
    expect(10).toBeGreaterThan(5);
  });

  test('exceptions', () => {
    const throwError = () => {
      throw new Error('Something went wrong');
    };

    expect(throwError).toThrow();
    expect(throwError).toThrow('Something went wrong');
  });
});

    Soft Assertions

    Use expect.soft to continue test execution even when assertions fail:

    test('soft assertions', () => {
  expect.soft(1 + 1).toBe(3); // This will fail but test continues
  expect.soft(2 + 2).toBe(5); // This will also fail but test continues
  expect(3 + 3).toBe(6); // This passes
  // Test will be marked as failed due to soft assertion failures
});

    When multiple soft assertions fail, Harness reports all failure messages, but currently only the first failure contributes the highlighted stack trace and code frame.

    Complete API Reference

    Harness provides the complete Vitest expect API including:

    • Basic matchers: toBe, toEqual, toStrictEqual
    • Truthiness: toBeTruthy, toBeFalsy, toBeNull, toBeUndefined, toBeDefined
    • Numbers: toBeGreaterThan, toBeLessThan, toBeCloseTo
    • Strings: toMatch, toContain, toHaveLength
    • Arrays/Objects: toContain, toHaveProperty, toMatchObject
    • Exceptions: toThrow, toThrowError
    • Types: toBeInstanceOf, toBeTypeOf
    • Asymmetric matchers: expect.anything(), expect.any(), expect.arrayContaining(), etc.

    For the complete documentation of all available matchers and advanced features, please refer to the Vitest expect documentation.

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