Add comprehensive multi-generation targeting test matrix with diagnostic assertions

[Copilot]

Issue #77: Multi-generation targeting tests with diagnostic assertions

Summary: .NET 10 + TUnit Migration Fixes

The maintainer upgraded the project from .NET 9 to .NET 10 and converted from xunit to TUnit. This required several fixes to address broken tests.

Test Results:

State	Passed	Failed
Initial (after migration)	307	39
After validator fixes	312	34
After Logger pipeline fix	316	30

Key Fixes Made:

1. global.json - Updated SDK version to 10.0.100

2. TelemetryMethodValidator.cs:

   • Fixed IsObservableMetricsReturnType to properly handle IEnumerable<Measurement<T>>
   • Fixed ShouldExcludeParameter to correctly exclude metrics measurement params from logging

3. PipelineHelpers.Logger.cs:

   • Added logic to skip methods with [Activity], [Event], [Context] attributes
   • Added logic to skip methods with metrics attributes ([Counter], [Histogram], etc.)
   • This prevents TSG2021 from being incorrectly raised for Activity methods in multi-target interfaces

4. Utilities.cs:

   • Added HasMetricsAttribute helper method

5. Snapshots:

   • Accepted 26 new/updated snapshots reflecting correct multi-target generation
   • Logging implementation now only includes [Log] methods

Remaining Issues (30 failures):

• Observable metrics return type validation issues
• Some diagnostic code assertion mismatches
• Multi-target edge cases (async methods, multiple attributes)
• These may require additional investigation or test updates

Commits:

• fc27f41: Update global.json to .NET 10.0.100
• d31bfa6: Fix TelemetryMethodValidator
• 4472c00: Fix Activity tests
• 1317bc4: Fix Logger pipeline for multi-target
• 787d39e: Accept new snapshots

Original prompt

Issue #77: Add a wide variety of tests to prove that multi-generation targetting is working with a matrix of options - targets/ exclusions.

Test for success and compilation and diagnostic expectations.

Update the test project and TUnit and Verify to make sure all supported frameworks work as expected.

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[kieronlanning]

@copilot Add the following two features if they don't already exist:

• When testing for diagnostics across the project, also assert on the expected diagostic code(s) to make it clear to the reader. Do this across the project.

[Copilot]

@copilot Add the following two features if they don't already exist:

• When testing for diagnostics across the project, also assert on the expected diagostic code(s) to make it clear to the reader. D...

Added diagnostic code assertions across the project. TestHelpers.Verify now accepts expectedDiagnosticCodes parameter and verifies the correct diagnostic IDs are present. Updated all 8 Multi Generation diagnostic tests to specify expected codes (TSG1001, TSG1002, TSG1003, TSG3012). Commit: f635967

[kieronlanning]

@copilot DateTimeOffset isn't something to be excluded - it's a basic type.

All tests should be updated to include the diagnostics. Not just the new multi-generation ones.

[Copilot]

@copilot DateTimeOffset isn't something to be excluded - it's a basic type.

All tests should be updated to include the diagnostics. Not just the new multi-generation ones.

Removed DateTimeOffset reference from documentation (it's only in generated code, not exclusion logic). Updated 21/33 diagnostic tests with expected codes across Activities, Metrics, and DuplicateMethodNames files. Continuing with remaining 12 tests in Logging folders. Commits: b1f8e6e, 3bdd6a1

[kieronlanning]

@copilot I've updated the project from .NET 9 to 10, and converted xunit to tunit.

Plan the next steps.

There are broken tests.

[Copilot]

@copilot I've updated the project from .NET 9 to 10, and converted xunit to tunit.

Plan the next steps....

Updated global.json to .NET 10.0.100 (commit fc27f41). Tests now run with TUnit.

Test Results: 307 passed, 39 failed, 346 total

Failing Test Categories:

1. Return type validation tests - ValidateReturnType_GivenObservableMetricsTypes_ReturnsValid
2. Parameter exclusion tests - ShouldExcludeParameter_GivenCounterValueForLogging_ReturnsExcluded
3. Generic method diagnostics - diagnostic code assertions not matching
4. Multi-generation tests - compilation errors in generated code (CS0535 interface not implemented, CS8632 nullable warnings)
5. Observable metrics tests - unexpected diagnostics in compilation

Next Steps:

1. Fix return type validation for observable metrics (IEnumerable<Measurement>)
2. Fix parameter exclusion logic for counter values
3. Update diagnostic code expectations in multi-generation tests
4. Investigate generated code compilation errors

@copilot I've updated the project from .NET 9 to 10, and converted xunit to tunit.

Plan the next steps....

Made significant progress on the .NET 10 + TUnit migration:

Test Results: 316 passed, 30 failed (improved from 307/39)

Fixes Applied:

1. Updated global.json to .NET 10.0.100 (fc27f41)
2. Fixed TelemetryMethodValidator for observable metrics types (d31bfa6)
3. Fixed Logger pipeline to skip Activity/Metrics methods in multi-target scenarios (1317bc4)
4. Accepted 26 new snapshots for correct multi-target generation (787d39e)

Remaining 30 failures need investigation:

• Observable metrics return type validation
• Diagnostic code assertion mismatches
• Multi-target edge cases (async methods, multiple attributes on same method)

These may require additional source generator fixes or test expectation updates.

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