[dblock]

Summary

• Run the full suite and installed-consumer integration task with development-only parallel_tests. Keep spec:unit unchanged and add spec:serial for serial debugging.
• Separate workflow and composite integration files around the existing shared scenarios so the two interfaces can run concurrently. Preserve all fresh-process release phases, package builds, real Git operations, credential checks, and recovery assertions.
• Give coverage workers distinct identities, discard stale resultsets before a run, and generate HTML/LCOV reports once after every worker exits, including failed runs. Preserve SPEC, SPEC_OPTS, and configurable worker counts.

Measured performance

Same machine, Ruby 4.0.9, seed 12345, and Open3 instrumentation; the parallel run used 12 workers.

These measurements used shared base 46f4573, before the subsequent rebase onto merged #53. The final rebased branch was validated separately against current master.

Metric	Before	After
Full-suite wall time	98.12 s	36.37 s
Examples	328	328
Covered lines	1803 / 1821	1803 / 1821

62.9% less wall time, or 2.70x faster. Every covered and uncovered source line is identical, not just the coverage percentage.

Observed Open3 launches inside spec workers: Bash 119 -> 119, Ruby/Rake 78 -> 78, other Ruby 40 -> 40, and Git 1062 -> 1059. These counts exclude descendant processes inside release phases and the parallel runner's own worker launches.

This trades concurrent CPU use for wall time rather than removing scenarios. Set PARALLEL_TEST_PROCESSORS=2 to limit workers, or use bundle exec rake spec:serial.

Validation

• After rebasing onto Add reusable Markdown section updates #53: full default task passes with 342 examples, 1854 / 1872 covered lines, and 148 RuboCop files without offenses; gem construction also passes.
• Before that rebase: all 17 integration examples pass against the installed archive with two workers.
• Deliberately failing worker propagates failure; unmatched file selection is rejected; serial fallback executes the selected example.

Created by an AI assistant on behalf of @dblock.