Add unit tests for Xamarin.Android.Tools.Aidl.CSharpCodeGenerator

[Copilot]

CSharpCodeGenerator had limited unit coverage — the existing 6 tests mirrored the MSBuild integration tests in AidlTest.cs, leaving several generator code paths only reachable via expensive MSBuild builds.

Changes

• AidlCompilerTestBase — RunTest now takes an optional ParcelableHandling so generator behavior under each mode is exercisable.
• New CSharpCodeGeneratorTests fixture targeting previously-uncovered code paths:
  • ParcelableIgnore / ParcelableStub / ParcelableError — all three ParcelableHandling branches (the StubParcelable method had no coverage).
  • MultipleInterfaces — multiple interface declarations in a single compilation unit.
  • OnewayMethods — oneway methods omit reply.WriteNoException () in OnTransact.
  • IBinderTypes — IBinder parameters/returns route through WriteStrongBinder / ReadStrongBinder.
  • CharSequenceType — CharSequence maps to Java.Lang.ICharSequence via Android.Text.TextUtils.
  • ParseErrorIsReported — invalid AIDL surfaces parser messages with null output.
• 6 new TestData/*.txt golden files, generated via the existing GENERATE_OUTPUT workflow and inspected.

Example

[Test]
public void ParcelableStub () => RunTest (nameof (ParcelableStub), ParcelableHandling.Stub);

[Test]
public void ParcelableError ()
{
    const string input = "package com.xamarin.test;\nparcelable MyData;\n";
    var compiler = new AidlCompiler ();
    Assert.Throws<InvalidOperationException> (() =>
        compiler.Run (input, out _, parcelableHandling: ParcelableHandling.Error));
}

Note for reviewers

The OnewayMethods golden output captures a pre-existing quirk: the generated Proxy still calls __reply.ReadException () even though the stub side skips reply.WriteNoException (). The test snapshots current behavior rather than asserting correctness; worth a follow-up if intentional asymmetry is not desired.

[Copilot]

Pull request overview

This PR expands unit test coverage for Xamarin.Android.Tools.Aidl.CSharpCodeGenerator by adding a focused NUnit fixture that validates previously-uncovered generator branches using golden TestData/*.txt snapshots, and by extending the shared test helper to vary ParcelableHandling.

Changes:

• Extend AidlCompilerTestBase.RunTest to accept an optional ParcelableHandling argument.
• Add CSharpCodeGeneratorTests covering parcelable modes, multiple interfaces, oneway methods, IBinder, CharSequence, and parse-error reporting.
• Add golden snapshot files for the new scenarios under tests/.../TestData/.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/Xamarin.Android.Tools.Aidl-Tests/AidlCompilerTestBase.cs	Adds ParcelableHandling parameter plumbing to exercise generator modes.
tests/Xamarin.Android.Tools.Aidl-Tests/CSharpCodeGeneratorTests.cs	New NUnit fixture targeting specific generator code paths without MSBuild integration tests.
tests/Xamarin.Android.Tools.Aidl-Tests/TestData/ParcelableStub.txt	Golden output for ParcelableHandling.Stub.
tests/Xamarin.Android.Tools.Aidl-Tests/TestData/ParcelableIgnore.txt	Golden output for ParcelableHandling.Ignore.
tests/Xamarin.Android.Tools.Aidl-Tests/TestData/OnewayMethods.txt	Golden output for method-level oneway generation behavior.
tests/Xamarin.Android.Tools.Aidl-Tests/TestData/MultipleInterfaces.txt	Golden output for multiple interfaces in one compilation unit.
tests/Xamarin.Android.Tools.Aidl-Tests/TestData/IBinderTypes.txt	Golden output for IBinder parameter/return codegen.
tests/Xamarin.Android.Tools.Aidl-Tests/TestData/CharSequenceType.txt	Golden output for CharSequence mapping via Android.Text.TextUtils.