Code coverage

Enable coverage when constructing the engine:

csharp

var engine = new Engine(options => options.Coverage.Enabled = true);

engine.Execute("""
    function sign(n) {
        if (n >= 0) return "positive";
        return "negative";
    }
    sign(1);
    """, "rules.js");

foreach (var source in engine.Diagnostics.GetCoverage().Sources)
{
    foreach (var entry in source.Entries)
    {
        Console.WriteLine(
            $"{source.Name}:{entry.Start.Line} {entry.Kind} x{entry.HitCount}");
    }
}

Coverage counts entries into executed constructs. A loop statement can be hit repeatedly; a function body is counted per call and per generator or async resumption.

Options.Coverage.Granularity defaults to CoverageGranularity.Statements. Set it to CoverageGranularity.Functions to collect function-body entries only.

Only executed constructs appear. The report is a covered set, not a percentage; walk the prepared AST when a denominator is required. Block statements themselves are omitted.

Counters belong to an engine, not a Prepared<Script>, so engines sharing one prepared AST retain independent measurements. A source represents one parse, even when another parse has the same source name. Reusing a prepared script keeps one source identity.

Start another measurement with:

csharp

engine.Diagnostics.ResetCoverage();

GetCoverage and ResetCoverage throw if coverage was not enabled. Collection uses the instrumented per-statement interpreter path and disables tight-loop optimizations; it is intentionally off by default and should not be enabled for performance measurements.

Code coverage ​

Code coverage