NSubstitute参数匹配时Returns被忽略问题排查

Let's break down why your mocked ILicenseChecker.IsEnabled isn't returning the expected enabled value, and how to fix it:

1. Your DI Container Might Not Be Injecting the Mocked License Checker #

The most likely culprit here is that MApplication.Container.Resolve<IEntityDefinitionQuerying> isn't actually using the mocked licenseChecker you passed via TypedParameter. Many DI containers prioritize pre-registered instances over inline parameters, so if your container already has a registered implementation of ILicenseChecker, it'll ignore your substituted instance.

How to Verify & Fix: #

• Debug Check: After resolving querying, inspect its internal ILicenseChecker field (via debugger or reflection) to confirm it's the substitute you created.
• Temporary Registration Override: Instead of relying on TypedParameter, temporarily replace the container's registered ILicenseChecker with your mock:

  public async Task<T> QuerySingleDefinition<T>(Func<IEntityDefinitionQuerying, EntityDefinition, Task<T>> target, bool enabled)
  {
      var definition = await CreateDefinition().ConfigureAwait(false);
  
      var licenseChecker = Substitute.For<ILicenseChecker>();
      licenseChecker.IsEnabled(Arg.Is<EntityDefinition>(p => p.Id == definition.Id), Arg.Any<User>()).Returns(Task.FromResult(enabled));
  
      // Save original registration to restore later
      var originalRegistration = MApplication.Container.GetRegistration(typeof(ILicenseChecker));
      try
      {
          // Register the mock as the current instance
          MApplication.Container.RegisterInstance(licenseChecker);
          var querying = MApplication.Container.Resolve<IEntityDefinitionQuerying>();
  
          return await target(querying, definition).ConfigureAwait(false);
      }
      finally
      {
          // Restore original registration to avoid breaking other tests
          if (originalRegistration != null)
          {
              MApplication.Container.Register(originalRegistration);
          }
          else
          {
              MApplication.Container.Unregister(typeof(ILicenseChecker));
          }
      }
  }
  

2. Your Argument Matching Condition Isn't Being Met #

Even if the mock is injected correctly, the Arg.Is<EntityDefinition>(p => p.Id == definition.Id) condition might not be triggering. This could happen if:

• The EntityDefinition passed to IsEnabled in your target delegate is a different instance (e.g., cloned or reloaded) with the same Id (though the Id check should still work if it's a value type like Guid or int).
• The definition.Id value changed between when you created the mock and when IsEnabled is called.
• You're dealing with a reference-type Id (like a custom class) where equality isn't properly implemented.

How to Verify & Fix: #

• Log or Debug the Parameters: Add a callback to your mock to inspect the actual parameters being passed:

  licenseChecker.When(x => x.IsEnabled(Arg.Any<EntityDefinition>(), Arg.Any<User>()))
                .Do(call => 
                {
                    var passedDef = call.Arg<EntityDefinition>();
                    // Compare passedDef.Id to definition.Id here (debug or log)
                });
  

• Simplify the Match: If the Id is a value type, you can bypass the object check and match directly on the Id (if IsEnabled has an overload that accepts the Id instead of the full EntityDefinition):

  licenseChecker.IsEnabled(definition.Id, Arg.Any<User>()).Returns(Task.FromResult(enabled));
  

3. Method Signature Mismatch #

Double-check that the IsEnabled method signature you're mocking exactly matches what's being called in target. For example:

• Are the parameter types correct? (Is the second parameter really User, or a derived type?)
• Are there overloads of IsEnabled that you're not accounting for? If target calls a different overload, your mock configuration won't apply.

How to Verify & Fix: #

• Check the ILicenseChecker interface definition to confirm the exact signature of IsEnabled.
• If overloads exist, explicitly specify parameter types in your mock setup to avoid ambiguity:

  licenseChecker.IsEnabled(Arg.Is<EntityDefinition>(p => p.Id == definition.Id), Arg.Any<User>())
                .Returns(Task.FromResult(enabled));
  

内容的提问来源于stack exchange，提问作者Gakuo