fix(codecov): sweep stale XML files via sentinel-file guard (#125)

[rossaddison]

Problem

PhpUnitXmlReport::generate() writes per-file XMLs into <outputDir> but never cleans old files between runs. When a source file is renamed or deleted, its corresponding XML remains, leaving Infection (and any other consumer) with ghost entries.

Approach — sentinel-file guard

On the first successful run a file .testo-coverage is created inside <outputDir>. On every subsequent run, if the sentinel is present the directory is known to belong to this reporter, so all *.xml files are removed before the new set is written.

If the sentinel is absent (e.g. <outputDir> is pointed at an unrelated directory), no sweeping takes place — protecting against accidental data loss.

This is the approach suggested by the maintainer in issue #125.

Changes

• PhpUnitXmlReport::generate() — check/touch sentinel, call sweepStaleXml() when present
• PhpUnitXmlReport::sweepStaleXml() — RecursiveIteratorIterator deletes *.xml files only (non-XML files untouched)
• private const SENTINEL = '.testo-coverage' — name is a constant for easy discoverability
• Class-level PHPDoc updated to document the stale-file guard behaviour
• Three new tests covering the acceptance criteria from the issue:
  • reRunSameSourceSetProducesNoStaleFiles — idempotent re-runs don't accumulate files
  • reRunAfterFileRemovedCleansStaleXml — deleted source file's XML is removed on next run
  • firstRunOnNonEmptyDirectoryWithoutSentinelLeavesExistingFilesAlone — no sweep without sentinel

Test results

Suite: Codecov/Unit — 119 tests · 119 passed (0 skipped/failed)

All pre-existing tests pass unchanged; no index.xml content or <file href> semantics were altered.

Fixes #125

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[rossaddison]

PR Summary

Three commits, two problems fixed.

Issue #125 — stale XML files in PhpUnitXmlReport

generate() wrote per-file XMLs into <outputDir> but never cleaned up between runs. When a source file was renamed or deleted, its XML persisted — leaving Infection (and any other consumer) with ghost entries.

Fix: sentinel-file guard in PhpUnitXmlReport::generate().

• On the first successful run, .testo-coverage is written inside <outputDir>.
• On every subsequent run, the sentinel's presence signals the directory is ours; all *.xml files are swept before the new set is written.
• If the sentinel is absent (directory not previously written by this reporter), no sweeping occurs — protecting against accidental data loss.

New tests (3):

• reRunSameSourceSetProducesNoStaleFiles — idempotent re-runs don't accumulate files
• reRunAfterFileRemovedCleansStaleXml — deleted source file's XML is gone on the next run
• firstRunOnNonEmptyDirectoryWithoutSentinelLeavesExistingFilesAlone — foreign files survive when no sentinel is present

Infection mutant hardening

Three mutants escaped the initial run:

Mutant	Root cause	Fix
Concat / ConcatOperandRemoval on $sentinelPath	Both mutations place the sentinel alongside outputDir (e.g. /tmp/abc.testo-coverage) rather than inside it (/tmp/abc/.testo-coverage), but find it consistently on re-runs so the sweep still triggers	sentinelIsWrittenInsideOutputDir asserts file_exists($dir . '/.testo-coverage') and !is_file($dir . '.testo-coverage')
LogicalAnd → || in sweepStaleXml()	RecursiveIteratorIterator::LEAVES_ONLY only yields files, so isFile() is always true and && vs || are equivalent	Removed the redundant isFile() check; added a comment explaining the invariant

Pre-existing CI fix — EmptyRunTest in PHPUnit mirror

tests/Application/Stub/EmptyRun/ is an intentionally empty directory (only .gitkeep). The PHPUnit mirror build (bin/build-phpunit.php) copies only *.php files, so tests/PhpUnit/Application/Stub/EmptyRun/ was never created in CI. The mirrored EmptyRunTest resolves __DIR__ . '/../../Stub/EmptyRun' to that missing path and threw InvalidArgumentException, aborting Infection's initial PHPUnit run on every push to 1.x since 2026-07-03.

Fix: added .placeholder.php (no namespace, no classes, no tests) to the source directory. The build script copies it into the mirror, creating the required directory. Testo's FinderConfig still discovers zero tests there, so Status::Risky is reported and the existing assertion holds.