Add unit test for ImageListCodeDomSerializer

[John-Qiao]

Related #10773

Proposed changes

• Add unit test ImageCollectionCodeDomSerializerTests.cs for public Deserialize() method of the ImageCollectionCodeDomSerializer.
• Enable nullability in ImageCollectionCodeDomSerializerTests.cs.

Microsoft Reviewers: Open in CodeFlow

[ricardobossan]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.15627%. Comparing base (084e6d0) to head (3e96033).
Report is 48 commits behind head on main.

Additional details and impacted files

@@                 Coverage Diff                 @@
##                main      #12753         +/-   ##
===================================================
+ Coverage   76.03186%   76.15627%   +0.12441%     
===================================================
  Files           3181        3193         +12     
  Lines         639670      640294        +624     
  Branches       47215       47238         +23     
===================================================
+ Hits          486353      487624       +1271     
+ Misses        149797      149163        -634     
+ Partials        3520        3507         -13     

Flag	Coverage Δ
Debug	76.15627% <100.00000%> (+0.12441%)	⬆️
integration	18.16436% <ø> (-0.01192%)	⬇️
production	50.06432% <ø> (+0.24233%)	⬆️
test	97.01938% <100.00000%> (-0.00978%)	⬇️
unit	47.24706% <ø> (+0.20415%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

[Tanya-Solyanik]

Please use 4 spaces to indent code.

[Tanya-Solyanik]

If you want to align dots, you can do this -

        managerMock
            .Setup(m => m.GetSerializer(typeof(Component), typeof(CodeDomSerializer)))
            .Returns(baseSerializerMock.Object);

[ricardobossan]

Please declare variables with their specifc types, e.g.:

Mock<IDesignerSerializationManager> managerMock = new();
Mock<CodeDomSerializer> baseSerializerMock = new();

This happens other times in this PR's code.

[ricardobossan]

This test doesn't correctly trigger the expected codepath to return null. The Deserialize method only returns null by chance, making the test pass incorrectly:

To ensure the test executes the intended codepath, the mock setup should return false:

Additionally, since the correct code path contains a Debug.Fail() call, you'll need to clear the Trace.Listeners to prevent the test from halting prematurely. Here's the corrected test code:

[Fact]
public void Deserialize_ShouldReturnNull_WhenBaseSerializerNotFound()
{
    Mock<IDesignerSerializationManager> managerMock = new();
    Mock<CodeDomSerializer> baseSerializerMock = new();

    managerMock.Setup(m => m.GetSerializer(typeof(Component), typeof(CodeDomSerializer)))
             .Returns(false);

    Trace.Listeners.Clear();

    object codeObject = new();
    object? result = _serializer.Deserialize(managerMock.Object, codeObject);

    result.Should().BeNull();
}

[ricardobossan]

Could increase code coverage a bit by adding a test case to the Serialize method like this:

[Fact]
public void Serialize_ShouldGenerateCodeStatements_ForImageListWithKeys()
{
    Mock<IDesignerSerializationManager> managerMock = new();
    Mock<CodeDomSerializer> baseSerializerMock = new();
    ImageList imageList = new();
    imageList.Images.Add("Key1", new Bitmap(1, 1));
    imageList.Images.Add("Key2", new Bitmap(1, 1));

    baseSerializerMock.Setup(b => b.Serialize(managerMock.Object, imageList)).Returns(new CodeStatementCollection());

    managerMock.Setup(m => m.GetSerializer(typeof(Component), typeof(CodeDomSerializer)))
             .Returns(baseSerializerMock.Object);

    ContextStack contextStack = new();
    contextStack.Append(new ImageListCodeDomSerializer());
    managerMock.Setup(m => m.Context).Returns(contextStack);

    object? result = _serializer.Serialize(managerMock.Object, imageList);
    result.Should().BeOfType<CodeStatementCollection>();
}