public async Task AddCountry_ShouldNotAdd_WhenCountryExists() { // Arrange var responseMessage = "Country already exists."; _unitOfWorkMock.Setup(x => x.Countries.Exists(It.IsAny <string>())) .ReturnsAsync(true); // Act var result = await _sut.AddCountry(It.IsAny <string>()); // Assert Assert.Equal(responseMessage, result.Value); }