Karma tests only run half the time in Docker environment

Are there any known race conditions that happen when Karma is used with Docker? The test runs correctly sometimes. Example: I run karma start and the tests don’t run correctly (shown below), but when I run it a second time, it might run correctly (also shown below).

Expected behaviour

The tests run consistently every time the karma server is started with ./node_modules/karma/bin/karma start ./karma.conf.ts. I am in a Docker environment.

Actual behaviour

Sometimes, the tests run to completion correctly. Other times, the tests do not run at all.

When the tests run correctly:

When the tests don’t run correctly:

Environment Details

• Karma version (output of karma --version): 4.2.0
• Relevant part of your karma.config.js file

[semanio]

@johnjbarton - make sense. I am definitely in CONFIGURING_DISCONNECTED state with this situation. I’ll see if I can work up that fix.

To be clear; in this case, it’s not calling browser_start at all in this situation without my proposed fix. I am actively testing that out though against a small test suite to be sure. Regardless, what you are saying as the proper fix makes sense.

[johnjbarton]

Unfortunately the reporters are not designed to be resilient to reconnect. They may assume two browsers exist if the browser_start is sent twice. So we can’t send browser_start twice.

I guess we need to introduce another state, CONFIGURING_DISCONNECTED to ensure that EXECUTING_DISCONNECTED always means that we did enter EXECUTING before disconnect. In your scenario, your disconnect should be during CONFIGURING_DISCONNECTED and when you get to reconnect you can verify that state and emit browser_start to enter EXECUTING.

Does that make sense?