Am I writing my unit tests correctly? NUnit + NSubstitute

Question

Recently, I began to learn how to write unit tests, as well as what part of a module to test for functionality and what to do. I use NSubstitute as my mocking structure. My example basically calls the repo class, which then makes a WEB API web call to an external service, i.e. AddCreditCard, which then returns the result. I created 2 unit tests for AddCreditCard, one for success and one for Fail. I'm still not 100% sure that I'm doing everything right. Unit tests pass, but I'm not sure that my Asserts are running with the correct data ... All help and suggestions are welcome!

public interface IApiResponse<T>
{
    HttpStatusCode StatusCode { get; set; }
    T Result { get; set; }
    string ErrorMessage { get; }
    bool HasErrors { get; }
}

public interface ISignedRequest
{
    void ConfigureSettings(SignedRequestSettings settings);

    IApiResponse Post(string jsonData, Dictionary<string, string> parameters = null,
        IOptionalHeaders optionalHeaders = null);
}


public class PaymentRepository
{
    private readonly SignedRequestSettings _settings;
    private readonly ISignedRequest _signedRequest;

    public PaymentRepository(ISignedRequest signedRequest = null)
    {
        if (signedRequest == null)
            _signedRequest = new SignedRequest();
        else
            _signedRequest = signedRequest;
    }

    public IApiResponse AddCreditCard(CreditCard request)
    {
        var jsonData =
            JsonConvert.SerializeObject(request);

        string action = string.Format("customers/{0}/paymentmethods", request.ConnectId);
        _settings.Url = string.Format("{0}{1}", String.Empty, action);
        _signedRequest.ConfigureSettings(_settings);

        return _signedRequest.Post(jsonData);
    }
 }

    [Test]
    public void AddCreditCard_GivenValidCreditCard_ReturnsCreatedResult()
    {
        //Given
        var apiResponse = Substitute.For<IApiResponse>();
        apiResponse.StatusCode = HttpStatusCode.Created;

        var signedRequest = Substitute.For<ISignedRequest>();
        signedRequest.Post(Arg.Any<String>()).Returns(apiResponse);

        var creditCard = Substitute.For<CreditCard>();
        creditCard.ConnectId = Guid.Parse("1fc1ad83-cd4e-4b68-bce6-e03ee8f47fb6");

        var repo = new PaymentRepository(signedRequest);

        //When
        var addCreditCardResponse = repo.AddCreditCard(creditCard);

        //Then
        signedRequest.Received(1).ConfigureSettings(Arg.Any<SignedRequestSettings>());
        signedRequest.Received(1).Post(Arg.Any<String>());

        Assert.AreEqual(HttpStatusCode.Created, addCreditCardResponse.StatusCode);
    }

[Test]
    public void AddCreditCard_GivenInvalidCreditCard_ReturnsHasErrorsResult()
    {
        //Given
        var apiResponse = Substitute.For<IApiResponse>();
        apiResponse.HasErrors.Returns(true);
        apiResponse.ErrorMessage.Returns("Add credit card error message");

        var signedRequest = Substitute.For<ISignedRequest>();
        signedRequest.Post(Arg.Any<String>()).Returns(apiResponse);

        var creditCard = Substitute.For<CreditCard>();
        creditCard.ConnectId = Guid.Parse("1fc1ad83-cd4e-4b68-bce6-e03ee8f47fb6");

        var repo = new PaymentRepository(signedRequest);

        //When
        var addCreditCardResponse = repo.AddCreditCard(creditCard);

        //Then
        signedRequest.Received(1).ConfigureSettings(Arg.Any<SignedRequestSettings>());
        signedRequest.Received(1).Post(Arg.Any<String>());

        Assert.AreEqual(apiResponse.HasErrors, addCreditCardResponse.HasErrors);
        Assert.AreEqual(apiResponse.ErrorMessage, addCreditCardResponse.ErrorMessage);
    }

Answer 1

, , , . :

signedRequest.Received(1).ConfigureSettings(Arg.Any<SignedRequestSettings>());
signedRequest.Received(1).Post(Arg.Any<String>());

, signedRequest ? , , , . , , ( - ).

-, , ( ). , , ConfigureSettings Post signedRequest. _signedRequest.Post("some random string");, . , , , . Received . - :

signedRequest.Received(1).ConfigureSettings(Arg.Is<SignedRequestSettings>(x=>x.Url == someHardCodedUrl));
signedRequest.Received(1).Post(someHardCodedJsonString);