moq verify method was called with stream of data

Question

I have a method that calls another method with a stream. I would like to test that the data inserted in the first method is what is sent in the second.

public MyMessage Parse(byte[] data)
{
    return myDependency.Read(new MemoryStream(data))
}

In my test, I have something like the following

byte [] mockData = { 116, 101, 115, 116};

sut.Parse(mockData);

mockDependency.Verify(x=>x.Read(...));

Now my question is, what is the correct thing I should have in place of ...?

I can do something like (It.IsAny<MemoryStream>()), but that does not actually verify that it was called with the given data.

I tried something like It.Is<MemoryStream>(s=>s.Equals(new MemoryStream(data))) but that failed.

Is there a way for me to test that the data sent to Parse is the same data send in the memory stream to Read?

Answer 1

I tried something like It.Is<MemoryStream>(s=>s.Equals(new MemoryStream(data))) but that failed.

In this case it could have been done like

mockDependency.Verify(_ => _.Read(It.Is<MemoryStream>( s => 
    Enumerable.SequenceEqual(s.ToArray(), data))));

by comparing the byte arrays

You can also try capturing the passed argument so that is can be better inspected during assertion

For example

// Arrange
byte [] expectedData = { 116, 101, 115, 116 };
byte [] actualData = null;

//...

mockDependency
    .Setup(_ => _.Read(It.IsAny<MemoryStream>()))
    .Callback((MemoryStream ms) => actualData = ms.ToArray())
    .Returns(/* MyMessage here*/)
    .Verifiable();

// Act
sut.Parse(expectedData);

//Assert
mockDependency.Verify(); //verify that setup was invoked as expected
//using FluentAssertions to check data
actualData.Should().NotBeNull()
.And.BeEquivalentTo(expectedData);

Note that Fluent Assertions was used to simplify the assertion of the collection.