Add unit tests for PerfDiff core infrastructure (BenchmarkFileReader & Data Contracts)

[coderabbitai[bot]]

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Overview

This issue covers testing the foundational components of PerfDiff that handle file I/O and data modeling.

Scope

Components to Test

• BenchmarkFileReader - JSON file reading and deserialization
• Data Contracts - All model classes in BDN/DataContracts/
  • BdnResult, BdnResults, Benchmark, BdnComparisonResult
  • Statistics, Percentiles, Memory, Measurement
  • HostEnvironmentInfo, ConfidenceInterval, ChronometerFrequency
  • BenchmarkComparisonResult, RegressionResult

Test Scenarios

1. Valid File Reading

   • Successfully read valid BenchmarkDotNet JSON files
   • Correct deserialization of all properties
   • Handle multiple files in parallel

2. Error Scenarios

   • File not found
   • Invalid JSON format
   • Missing required properties
   • Empty files
   • Permission denied

3. Data Contract Validation

   • Property getters/setters work correctly
   • Record types behave as expected
   • Nullable properties handle null values
   • ToString() methods (where implemented)

Test Data Requirements

• Create sample valid BenchmarkDotNet JSON files
• Create malformed JSON files for error testing
• Represent various benchmark scenarios (different metrics, memory usage, etc.)

Acceptance Criteria

• [ ] BenchmarkFileReader has 100% test coverage
• [ ] All data contracts have basic property tests
• [ ] Error handling scenarios are thoroughly tested
• [ ] Sample test data files are created and committed
• [ ] Tests follow xUnit patterns used in the repository
• [ ] All tests pass and run efficiently

Implementation Notes

• Place tests in tests/PerfDiff.Tests/ (new test project)
• Use xUnit testing framework
• Follow existing test patterns in tests/Moq.Analyzers.Test/
• Mock file system operations where appropriate
• Use Theory and InlineData for data-driven tests

Related

• Parent issue: #[MAIN_ISSUE_NUMBER]
• Components: src/tools/PerfDiff/BDN/BenchmarkFileReader.cs, src/tools/PerfDiff/BDN/DataContracts/