[samtrion]

Problem

Mutation run 40488160594 reports MeasurementScopeExtensions.cs with 1 NoCoverage mutant (block removal of return NullScope.Instance;) and 2 surviving statement mutants (ArgumentNullException.ThrowIfNull(logger) and ArgumentException.ThrowIfNullOrWhiteSpace(identifier) in StartMeasurement). Log: 1 mutants got status NoCoverage, Killed: 16, Survived: 3, final mutation score is 80.00 %. No existing test passes LogLevel.None. (The HTML report is not part of the logs; the third survivor is assumed to be the Stopwatch.Stop one from the arithmetic, not verified.)

Root cause

The completionLevel is LogLevel.None branch is never executed. The two guards are only observable on that branch, since MeasurementScope's constructor repeats the same checks (same parameter names) for all other levels, so removing them is invisible without a None test.

Change

Unit tests only, in MeasurementScopeExtensionsTests.cs: LogLevel.None returns NullScope.Instance; null logger throws ArgumentNullException("logger"); null identifier throws ArgumentNullException("identifier"); empty/whitespace identifier throws ArgumentException("identifier").

Before / After

metric	before	after
mutation score	80.00 %	95.00 %
NoCoverage	1	0
survived	3	1
killed	16	19
Stryker time elapsed	n/a	37.7 s

Risk / what this does not change

No production code changes. The Stopwatch.Stop survivor is not addressed. Measured on the branch: https://github.com/dailydevops/logging.measurement/actions/runs/40804802841

Run: https://github.com/dailydevops/fluentvalue/actions/runs/40804673608

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.53%. Comparing base (b5aad10) to head (bb73d5d).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #613      +/-   ##
==========================================
- Coverage   98.54%   98.53%   -0.01%     
==========================================
  Files          22       22              
  Lines         274      273       -1     
  Branches       43       43              
==========================================
- Hits          270      269       -1     
  Misses          1        1              
  Partials        3        3              

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