public async void GetAllEmployeesAsync_ShouldReturnEmployeesList() { // Arrange var employees = new List <Employee> { new Employee { Id = 1, FirstName = "John", LastName = "Dou", MediaInteractivaEmployee = true, Pet = new Pet { Id = 32, Name = "Dick", Type = "duck", OwnerId = 1 } }, new Employee { Id = 2, FirstName = "Sam", LastName = "Smith", MediaInteractivaEmployee = false, Pet = new Pet { Id = 45, Name = "Mat", Type = "cat", OwnerId = 2 } } }; var employeesRepoMock = new Mock <IBaseRepository <Employee> >(); employeesRepoMock.Setup(x => x.GetAllAsync()).ReturnsAsync(employees); var employeesService = new EmployeesService(employeesRepoMock.Object); // Act var result = await employeesService.GetAllEmployeesAsync(); // Arrange Assert.IsAssignableFrom <IEnumerable <Employee> >(result); Assert.Equal(employees.Count, result.Count()); }