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Coverage buffer that loses its initialization byte is reported as a passing run with an empty report (line-rate="1")

Aperta
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Valutazione

Difficoltà
4/5
Tempo stimato
3-5 giorni
Idoneità per principianti
52/100
Tipo di issue
Bug
Chiarezza
Abbastanza chiara
Stato di attività
Attiva
Stack tecnologico
csharp
Ambito
testing-qa, tooling

Direzione di ricerca

Start by tracing SharedMemoryStream.IsInitialized() through the collector path described in the issue, including the guards around AddPackage, AddStream, and PopulateCoverageStatus. Reproduce the offset-0 corruption using the harness and results linked from issue #232. Done means an uninitialized module buffer is made visible as an anomaly rather than producing a passing empty report that satisfies coverage thresholds.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

Package: Microsoft.Testing.Extensions.CodeCoverage 18.11.2 (the latest at the time of writing)
Runtime: .NET 8 and .NET 10 hosts, Linux x64, xunit.v3 3.2.2 on Microsoft.Testing.Platform
Context: split out of #232, which 18.11.2 fixed. The harness and full results are in this comment.

Summary

If a module's coverage buffer loses its initialization byte, the run is reported as Passed! and the cobertura report is 178 bytes, with line-rate="1" over an empty <packages />. A coverage threshold passes it, so the data loss goes unnoticed.

Cause

The byte at offset 0 of the buffer is read by SharedMemoryStream.IsInitialized(). It gates whether a module enters the report at all: if (logStream.IsInitialized()) guards AddPackage, AddStream and PopulateCoverageStatus. Truncating the buffer zeroes that byte, and the host's flush writes only the indices where a probe fired, so index 0 is never restored.

Two runs isolate it to that byte, rather than to the data loss itself:

what was done to the buffer cobertura
write a single zero byte to offset 0; file length and all 1,356 probe bytes left intact 178 bytes, line-rate="1"
truncate to 0, re-extend to the original length, then set offset 0 back to 1 337,297 bytes, line-rate="0.027"

The direction matters. When the flag survives, the report shows a low rate that honestly reflects the destroyed data, and any coverage threshold catches it. When the flag is lost, the report shows a perfect rate over zero lines, which every threshold passes.

Suggestion

The collector created the buffer and handed it to the host, so a module whose buffer comes back uninitialized is an anomaly it can detect, not a normal skip. Logging a warning at that point, or failing the coverage step, would make this loss visible.

Lingua principale
C#
Stelle
125
Fork
17
Merge medio
1h 15m
PR unite (30g)
2

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