[samtrion]

Problem

The mutation run reports a score of 33.33%, but it only measures Helper.cs.

• 246 mutants got status Ignored. Reason: Removed by exclude from code coverage filter (plus 6 "block already covered")
• 10 total mutants will be tested of 294 created (3 mutated variant projects: Roslyn4_7, Roslyn4_14, Roslyn5_6)
• final mutation score is 33.33 %
• Per file: IsPackableProjectDiagnosticAnalyzer.cs Ignored 59 + CompileError 4, OldProjectSupportDiagnosticAnalyzer.cs Ignored 23, Helper.cs Killed 10 + Ignored 2.

Root cause

Both analyzer classes carry [ExcludeFromCodeCoverage]. Stryker honours that attribute and removes all mutants in those types. The only real production logic (NED0001-0009, OLD0001) is therefore never mutated, although 25 tests exercise it. The stryker-config.json mutate globs do not exclude these files, so the attribute is the only cause.

Change

Remove [ExcludeFromCodeCoverage] and the now unused using System.Diagnostics.CodeAnalysis; from both analyzers. No other coverage exclusion config exists in the repo (the CodeCoverage package is referenced only by test projects).

Before / After

Run: https://github.com/dailydevops/defaults/actions/runs/40804488424

metric	before	after
mutants created	294	294
ignored by exclude-from-coverage filter	246	0
ignored by block-already-covered filter	6	48
compile errors	12	12
no coverage	20	136
tested	10	98
killed	10	75
survived	0	3
mutation score	33.33%	35.05%

The attribute-driven ignores dropped from 246 to 0 and tested mutants rose from 10 to 98 (75 killed, 3 survived). The score barely moves because the Roslyn4_14 variant still finds 0 tests ("Number of tests found: 0"), so its mutants (plus others) became NoCoverage (136). That is a separate problem and needs its own fix. The 3 survivors point to concrete test gaps and are not addressed here.

Risk / what this does not change

• Analyzers now appear in code-coverage reports; acceptable since tests cover them.
• The score may go down: new survivors will point to real test gaps, and the Roslyn4_14 variant reports 0 tests found, so its mutants may become NoCoverage. That is a separate problem and is not addressed here.
• Compile-error mutants (4 per project) stay compile errors. The "84 per project" figure is an upper bound.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (2f30f7b) to head (b29b5c9).

Additional details and impacted files

@@            Coverage Diff             @@
##              main      #680    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files            1         3     +2     
  Lines           16       134   +118     
  Branches         1        15    +14     
==========================================
+ Hits            16       134   +118     

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