karma-runner/karma

Ensure all stream buffers are drained before exiting process in single run mode.

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#742 opened on Sep 11, 2013

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help wantedtype: bugwindows

Description

After investigating a strange behavior on running karma with TeamCity on Windows, I noticed the following issue.

When running the following command in PowerShell:

karma start --single-run | Out-File C:\test.out

The writing function is non-blocking/asynchronous & the written/piped data can be buffered, which could lead to some test results being lost.

Karma needs to ensure that all buffers have been drained or that the writing functions have completed (if they are non-blocking) before exiting the process.

Contributor guide

Tech stack
nodejs
Domain
backendtestingdeveloper experience
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Node.js streamsasynchronous programming
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Examine the main process exit logic in Karma, likely in lib/server.js or similar. Look for where the process exits after single run. Investigate how stdout/stderr streams are handled and ensure all pending writes are completed before calling process.exit. The issue mentions PowerShell and Out File, but the core problem is generic buffering in Node.js streams.