# PR#94: Fixes for the Nightly Mutation Build

> This document describes the change of this pull request at the time it was made.
> Later pull requests may change the behaviour without updating it.

## The Problem

The first run of the build `mutation` (PR#93) on mih09, right after the merge on 2026-10-03, failed twice:

- PIT stopped in its coverage run: `BuildExecutorIntegrationTest` did not pass without mutation, although the normal test build on mih09 and PIT locally pass it.
- The deploy of v1.28.0, queued behind it, found no runtime bundle: `mutation` runs in `main`'s worktree, and its `cleanCommand: rm -rf build` deleted the bundle the test build had left there.

The run started at once instead of at 02:00, because the definition was new and the day's slot was due.

## The Solution

- `mutation` cleans only `build/reports/pitest` and `build/reports/codecharta`; PIT recompiles what changed, and the runtime bundle stays for the deploy.
- `mutation` runs at 00:00 UTC instead of 02:00: 01:00 or 02:00 in Germany, depending on daylight saving time, which UTC does not have; later nightly builds of other repositories follow it on mih09.
- `BuildExecutorIntegrationTest` no longer runs under PIT.
  Two probe builds on this branch, with PIT's verbose output, could not reproduce the failure: the spec passed alone and with every other spec.
  It is most likely a timing-dependent case; the best guess is Scenario#67.04, where `true` must use no measurable processor time, which one clock tick under PIT's instrumentation breaks.
  One failing spec in the coverage run aborts the whole night, and the spec costs 24-29 s per covering mutant.
  `BuildExecutor` shows mostly uncovered until its logic moves into unit tests.

## Follow-up PRs

- `BuildExecutor`: its decisions into small classes with unit tests (already planned in PR#93).
- Make the timing-dependent cases of `BuildExecutorIntegrationTest` robust, starting with Scenario#67.04.