Code Coverage

Prova includes built-in code coverage that works seamlessly with Native AOT. No external tools or symbol-based instrumentation required.

Quick Start

Run your tests with the --coverage flag:

dotnet run -- --coverage

This generates a coverage.lcov file in the current directory.

How It Works

Prova's source generator injects lightweight "hit probes" into each test:

1. Registration: Each test case gets a unique CoverageId
2. Tracking: At test execution start, CoverageRegistry.Hit(id) is called
3. Reporting: After all tests complete, LCOV data is emitted

// Generated code (simplified)
ExecuteDelegate = async () => {
    CoverageRegistry.Hit(0); // Probe injection
    // ... test execution
}

LCOV Output Format

The generated coverage.lcov follows the standard LCOV format:

TN:
SF:GeneratedTests.cs
DA:1,1
DA:2,0
LF:2
LH:1
end_of_record

• DA:<line>,<hits> — Data line showing hit count
• LF — Lines Found (total)
• LH — Lines Hit (executed)

Viewing Reports

Generate HTML reports using genhtml:

genhtml coverage.lcov --output-directory coverage-report
open coverage-report/index.html

Or use VS Code extensions like "Coverage Gutters" to visualize in-editor.

AOT Compatibility

Unlike traditional coverage tools that rely on:

• PDB/debug symbols
• Runtime instrumentation
• IL rewriting

Prova's coverage is source-level, making it fully compatible with Native AOT compilation.

Limitations

Current implementation tracks test method execution, not line-by-line coverage of application code. Future versions will support:

• Application code instrumentation
• Branch coverage
• Function coverage