How to mock static method in c#?

Question

I am writing test cases using xUnit. I am testing controller. Below is my controller.

public IActionResult UpdateOption([FromBody] OptionsUpdate optionsUpdate)
{
  var updatingUser = userResolver.GetUserNameFromController(this);
  try
  {
    OptionsUpdate optionsUpdateData = DataParser.MakeDateConsistent(optionsUpdate);
    optionService.Update(optionsUpdateData, updatingUser);
    return Ok();
  }
  catch (Exception e)
  {
    log.Error(e, "Failed to update option parameters");
    return BadRequest();
  }
}

Below is my test method.

[Fact]
public void OnSuccess_ShouldBeOk()
{
  controller.GetDependency<IOptionService>()
    .Update(Arg.Any<OptionsUpdate>(), Arg.Any<string>());

  var result = controller.Target.UpdateOption(new OptionsUpdate()) as StatusCodeResult;
  result.StatusCode.ShouldBe(200);
}

In the above code When unit test case is writing below line of code throwing error.

 OptionsUpdate optionsUpdateData = DataParser.MakeDateConsistent(optionsUpdate);

Below is the implementation of MakeDateConsistent

public static OptionsUpdate MakeDateConsistent(OptionsUpdate optionsUpdate)
{
  optionsUpdate.Values[Constants.OptionStoreUpdateKeys.OnRangeDate] = ConvertDDMMYYYYToYYYYMMDD(optionsUpdate.Values[Constants.OptionStoreUpdateKeys.OnRangeDate]);
  if (optionsUpdate.Values.ContainsKey(Constants.OptionStoreUpdateKeys.OffRangeDate))
  {
    if (optionsUpdate.Values[Constants.OptionStoreUpdateKeys.OffRangeDate] != string.Empty)
    {
      optionsUpdate.Values[Constants.OptionStoreUpdateKeys.OffRangeDate] = ConvertDDMMYYYYToYYYYMMDD(optionsUpdate.Values[Constants.OptionStoreUpdateKeys.OffRangeDate]);
    }
  }

  return optionsUpdate;
}

I edited my code as below.

var rawUpdate = new OptionsUpdate()
        {
          Keys = new List<OptionStore>()
        {
          new OptionStore() { Option = optionId, Store = store.ToString() }
        },
          Values = new Dictionary<string, string>()
        {
          { Constants.OptionStoreUpdateKeys.Lspl, lspl.ToString() },
          { Constants.OptionStoreUpdateKeys.OnRangeDate, "01/01/2018" },
        }
        };
        DataParser.MakeDateConsistent(rawUpdate).Returns(rawUpdate);

This is throwing error as

NSubstitute.Exceptions.CouldNotSetReturnDueToTypeMismatchException: 'Can not return value of type OptionsUpdate for IOptionService.Update (expected type Int32).

I dont want to create any interface to test this. Can someone help me to mock MakeDateConsistent static method?

It probably throws a NullReferenceException on `options.Values`? — CodeCaster, May 09 '19 at 06:52
I don't see any reasons to mock that method - it is pure function not taking any inputs except arguments and has no state. Should be perfectly fine to pass acceptable arguments instead of trying to mock it (but since you've asked I'll find good duplicate for it) — Alexei Levenkov, May 09 '19 at 06:53
Okay If i dont have to mock it then what should i do in order to avoid error? — Niranjan, May 09 '19 at 06:54
I don't think you need to do anything in particular to "avoid error" - if you pass unexpected/invalid arguments to a method it should throw exception (ideally `ArgumentException`, but it is somewhat acceptable to throw any exception in such case). — Alexei Levenkov, May 09 '19 at 06:57
What i have understood is static method cannot be mocked. So how to handle whenever satic method comes in code? — Niranjan, May 09 '19 at 07:09

score 1 · Answer 1 · answered May 09 '19 at 06:54

1

The question is, why do you need the method to be static? You should not use static methods that talk with other dependencies. They should at most work on their own properties and values. If they do, you do not have to mock them. Use a proper class and inject it for all other dependencies.

answered May 09 '19 at 06:54

andreasnico

1,478
14
23

Thanks. Can you give me any example? – Niranjan May 09 '19 at 06:56
@Niranjan check the answers to the question linked at the top – andreasnico May 09 '19 at 07:02
The link does not answer my question. – Niranjan May 09 '19 at 07:19
What is controller.Target? The test should say controller.UpdateOption(..) somewhere – andreasnico May 09 '19 at 07:27
private readonly MockProvider.TestTarget controller; – Niranjan May 09 '19 at 08:41

How to mock static method in c#?

1 Answers1