C#•2y ago

❔ Capture parameter value with Moq decorated with the 'in' keyword

Hello! I'm writing Unit Tests for a library with a lot of structs, which utilizes the in keyword to avoid unnecessary copies. The Moq library allows you to capture passed values to methods. For example

Action<string> newMessageHandler;
var captureMatch = new CaptureMatch<Action<string>>(capture => newMessageHandler = capture);
var messageManagerMock = new Mock<IMessageManager>();

messageManagerMock.Setup(managerInstance => managerInstance.Start(Capture.With(captureMatch)));

Action<string> newMessageHandler;
var captureMatch = new CaptureMatch<Action<string>>(capture => newMessageHandler = capture);
var messageManagerMock = new Mock<IMessageManager>();

messageManagerMock.Setup(managerInstance => managerInstance.Start(Capture.With(captureMatch)));

I've found solutions for capturing ref and out parameters. But nothing for in. I tried solving this some time ago, and only just now thought of asking here, so I do not have more fresh examples.

2 Replies

DenisOP•2y ago

Assume we have the following class we want to mock, and capture parameters passed to it:

public interface IMessageManager
  : IDisposable
{
  /// <summary>
  /// Starts the manager
  /// </summary>
  /// <param name="messageHandler">Incoming message handler</param>
  void Start(Action<string> messageHandler);

  /// <summary>
  /// Removes a message
  /// </summary>
  /// <param name="metadata">Message metadata reference to remove</param>
  /// <returns>True if operation was successful</returns>
  bool Remove(in XMLMessageMetadata metadata);

  /// <summary>
  /// Creates a message
  /// </summary>
  /// <param name="message">Message to create</param>
  /// <param name="path">Path to create the message at</param>
  /// <returns>True if operation was successful</returns>
  bool Create(in XMLMessage message, string path);
}

public interface IMessageManager
  : IDisposable
{
  /// <summary>
  /// Starts the manager
  /// </summary>
  /// <param name="messageHandler">Incoming message handler</param>
  void Start(Action<string> messageHandler);

  /// <summary>
  /// Removes a message
  /// </summary>
  /// <param name="metadata">Message metadata reference to remove</param>
  /// <returns>True if operation was successful</returns>
  bool Remove(in XMLMessageMetadata metadata);

  /// <summary>
  /// Creates a message
  /// </summary>
  /// <param name="message">Message to create</param>
  /// <param name="path">Path to create the message at</param>
  /// <returns>True if operation was successful</returns>
  bool Create(in XMLMessage message, string path);
}

And again, the XMLMessage and XMLMessageMetadata are readonly structs

Accord•2y ago

Looks like nothing has happened here. I will mark this as stale and this post will be archived until there is new activity.

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❔ Capture parameter value with Moq decorated with the 'in' keyword