Expected behaviour

When running Karma with singleRun = false and autoWatch = false I would expect to be able to schedule a new run as soon as the 'old' run is completed.

Actual behaviour

A race condition in clearContext can report a false error in the new run.

Environment Details

• Karma version (output of karma --version): 4.4.1
• Relevant part of your karma.config.js file

{
  singleRun: false,
  autoWatch: false
}

Steps to reproduce the behaviour

It is difficult to reproduce since it is a race condition. Essentially it can happen in this scenario:

const karam = require('karma');
const server = new karma.Server({ singleRun: false, watch: false });
await server.start();
function runUntilError() {
  karma.runner.run({}, exitCode => {
    if(exitCode === 0) {
       runUntilError();
    } else {
       console.log('Aha! Run errored');
    }
  });
}
runUntilError()

Triage

The problem is in the complete handler. Results are reported to the server before the context is cleared:

The clearContext function sets the reloadingContext flag and navigates away.

Now, just before the browser navigates away, the reloadingContext is reset by the next execution:

The concequence of this, is that the error is reported here:

Some of your tests did a full page reload!

However, I didn't reload any page.

Workaround

If you set client.clearContext to false, the context will not be cleared and there is no risk of this race condition.