test: use a unique temp dir in test_variable_in_filter

[eran132]

Problem

tests/API/OVAL/unittests/test_variable_in_filter.sh wrote its fixture to a
fixed path, /tmp/key_file, and the OVAL definition hardcoded /tmp as the
file_object / file_state path (#1924). A predictable, world-writable path
in a shared directory:

• races with parallel test runs (and with other users) on the same machine, and
• lets a pre-existing, unrelated /tmp/key_file left by someone else affect the
  result.

Fix

Adopt the isolation pattern already used by test_pcre_nonutf_characters.sh:

• The OVAL definition now uses a TEMP_DIR_PLACEHOLDER token instead of /tmp.
• The test copies the definition to a temp file, sed-substitutes a per-run
  mktemp -d directory, and creates the key_file fixture inside it.
• The temporary directory is removed on completion.

The filename pattern (^key_file$) and the evaluation logic are unchanged, so
the test asserts exactly the same OVAL behavior — just in an isolated location.

Verification

This is a test-only change. I verified mechanically (the full suite runs in CI):

• bash -n passes on the script.
• The sed substitution leaves zero TEMP_DIR_PLACEHOLDER occurrences and
  rewrites both <ns3:path> elements to the unique temp dir.
• The resulting OVAL definition is still well-formed XML.
• The key_file fixture is created in the temp dir as expected.

Fixes #1924

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR makes the test_variable_in_filter unit test more hermetic by avoiding hard-coded /tmp paths and instead using a dynamically created temporary directory.

Changes:

• Replaced /tmp in the OVAL XML with a placeholder path.
• Updated the shell test to create an isolated temp directory, patch the XML, and run the evaluation against the patched XML.
• Adjusted cleanup to remove generated temp artifacts.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
tests/API/OVAL/unittests/test_variable_in_filter.xml	Replaces hard-coded /tmp with TEMP_DIR_PLACEHOLDER for runtime substitution.
tests/API/OVAL/unittests/test_variable_in_filter.sh	Creates temp dir/file, substitutes placeholder in XML, runs eval against temp XML, and cleans up.

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[eran132]

Thanks for the review. Addressed in 47338aa:

• Cleanup on failure: added a cleanup() handler registered with trap ... EXIT, so the temp files and mktemp -d directory are removed even if an assert_exists fails under set -e.
• Backticks → $(...): switched, matching the sibling test_pcre_nonutf_characters.sh.
• sed -i portability: kept as-is intentionally — the sibling test_pcre_nonutf_characters.sh uses the identical sed -i "s;...;...;" form and these OVAL unit tests run on GNU/Linux CI, so this stays consistent with the existing convention rather than introducing a divergent in-place-edit approach.