# PR#157: The processor-time test burns until it measured enough, so a loaded host no longer turns it red

> **WARNING:** This document describes only the change applied in this PR.
> It may already be outdated once the next PR is merged.
> Historic PR-documentation is not maintained along with new PRs — treat it as a snapshot, not as current documentation.

## The Problem

The main build of `c218a0c` (PR#156) failed in `ProcessTreeCpuTimeIntegrationTest`, Scenario#67.01.
The test let a grandchild burn for two seconds of wall clock and expected more than 300 ms of processor time.
Five other builds ran on mih09 at the same time, so the loop got less than 300 ms.
The same code was green on its branch a few minutes before, and green again after a restart.

The burn was shorter than it looked, too.
The loop stopped at `date +%s` plus two, in whole seconds, so it ran between one and two seconds.

## Non-Goals

- No change to `ProcessTreeCpuTime` itself: the measurement was correct, the test asked for too much.
- No lower threshold: 300 ms is what proves the descent into the tree, far above what the root shell costs.

## The Solution

- The grandchild loops until it is stopped (`while :; do :; done`).
- The test samples every 100 ms and stops the loop once the tree has cost more than 300 ms.
  A deadline of 30 s ends the loop if the descent is broken; then the assertion fails as before.
- A loaded host makes the test slower, not red.
  On an idle machine it ends after about half a second, faster than the old two-second burn.
- `& wait` in the outer shell makes sure the loop runs as a grandchild, whatever `sh` the host has.
- The test kills the whole tree afterwards (`descendants()`), since a grandchild outlives its killed parent.
- The upper bound of 10 s stays: the loop stops one sampling step after the threshold.
- The local run under twelve busy loops per core stayed green with both versions.
  The red was not reproduced locally, so the proof is the reasoning above and the next loaded build.
- Werkbaum: PR#157 added to "Flaky tests fixed".
- Version 1.42.1, with an entry in the release notes.