import { isPromise } from '../is-promise';

describe('isPromise', () => {
  test('should return true for a Promise', () => {
    const promise = new Promise((resolve) => resolve('success'));
    expect(isPromise(promise)).toBe(true);
  });

  test('should return true for an object with a "then" function', () => {
    const fakePromise = { then: jest.fn() };
    expect(isPromise(fakePromise)).toBe(true);
  });

  test('should return false for a regular object', () => {
    const obj = {};
    expect(isPromise(obj)).toBe(false);
  });

  test('should return false for a function', () => {
    const func = () => {};
    expect(isPromise(func)).toBe(false);
  });

  test('should return false for null', () => {
    expect(isPromise(null)).toBe(false);
  });

  test('should return false for undefined', () => {
    expect(isPromise(undefined)).toBe(false);
  });

  test('should return false for a primitive type (string)', () => {
    expect(isPromise('string')).toBe(false);
  });

  test('should return false for a primitive type (number)', () => {
    expect(isPromise(42)).toBe(false);
  });

  test('should return false for a primitive type (boolean)', () => {
    expect(isPromise(true)).toBe(false);
    expect(isPromise(false)).toBe(false);
  });
});