Karma becomes unresponsive instead of failing

I'm starting my Karma like this (in Java) :

```java
ArrayList karmaTestCommand = new ArrayList();
boolean isWindows = System.getProperty("os.name").startsWith("Windows");
if (isWindows) {
karmaTestCommand.add("cmd"); //on Windows, NPM is not an executable, but a .cmd file
karmaTestCommand.add("/c");
}
karmaTestCommand.add("npm");
karmaTestCommand.add("run");
karmaTestCommand.add("test");

ProcessBuilder karmaProcessBuilder = new ProcessBuilder(karmaTestCommand);
karmaProcessBuilder.inheritIO();
Map karmaProcessEnv = karmaProcessBuilder.environment();
karmaProcessEnv.put("RIA_TESTSERVER_PORT", Integer.toString(testserverPort));
karmaProcessEnv.put("KARMA_SERVER_PORT", Integer.toString(karmaServerPort));
Process karmaProcess = karmaProcessBuilder.start();

boolean completed = new ProcessWatchDog(karmaProcess).waitFor(20, TimeUnit.MINUTES);
if (!completed) {
System.err.println("Tests timed out after 20 minutes!");
RIATestReport.writeTestTimeoutReport("target/junit_reports/test-results.xml", RunKarmaTests.class.getName());
}
```

This starts the following script :

```json
"scripts": {
"test": "karma start common/test/karma/karma.conf.js --singleRun=true || (exit 0)"
}
```

Due to some issue with Firefox on one of our Jenkins slaves, Karma behaves like this :

```
[java] 02 04 2019 14:06:25.834:WARN [launcher]: Firefox have not captured in 60000 ms, killing.
[java] 02 04 2019 14:06:25.891:DEBUG [launcher]: Process Firefox exited with code 0
[java] 02 04 2019 14:06:25.891:DEBUG [temp-dir]: Cleaning temp dir C:\Users\release\AppData\Local\Temp\karma-95416947
[java] 02 04 2019 14:06:25.897:INFO [launcher]: Trying to start Firefox again (1/2).
[java] 02 04 2019 14:06:25.897:DEBUG [launcher]: Restarting Firefox
[java] 02 04 2019 14:06:25.897:DEBUG [temp-dir]: Creating temp dir at C:\Users\release\AppData\Local\Temp\karma-95416947
[java] 02 04 2019 14:06:25.898:DEBUG [launcher]: C:\Program Files\Mozilla Firefox\firefox.exe http://localhost:51005/?id=95416947 -profile C:\Users\release\AppData\Local\Temp\karma-95416947 -no-remote
[java] 02 04 2019 14:07:25.898:WARN [launcher]: Firefox have not captured in 60000 ms, killing.
[java] 02 04 2019 14:07:25.961:DEBUG [launcher]: Process Firefox exited with code 0
[java] 02 04 2019 14:07:25.961:DEBUG [temp-dir]: Cleaning temp dir C:\Users\release\AppData\Local\Temp\karma-95416947
[java] 02 04 2019 14:07:25.967:INFO [launcher]: Trying to start Firefox again (2/2).
[java] 02 04 2019 14:07:25.967:DEBUG [launcher]: Restarting Firefox
[java] 02 04 2019 14:07:25.967:DEBUG [temp-dir]: Creating temp dir at C:\Users\release\AppData\Local\Temp\karma-95416947
[java] 02 04 2019 14:07:25.968:DEBUG [launcher]: C:\Program Files\Mozilla Firefox\firefox.exe http://localhost:51005/?id=95416947 -profile C:\Users\release\AppData\Local\Temp\karma-95416947 -no-remote
[java] 02 04 2019 14:08:25.968:WARN [launcher]: Firefox have not captured in 60000 ms, killing.
[java] 02 04 2019 14:08:26.038:DEBUG [launcher]: Process Firefox exited with code 0
[java] 02 04 2019 14:08:26.038:DEBUG [temp-dir]: Cleaning temp dir C:\Users\release\AppData\Local\Temp\karma-95416947
[java] 02 04 2019 14:08:26.045:ERROR [launcher]: Firefox failed 2 times (timeout). Giving up.
```

This causes Karma to become unresponsive and will result in the process reaching a timeout after 20 minutes.

Is there any was I can get this process to end immediately, so I don't block my Jenkins slave for nothing?

Start with the npm test script and common/test/karma/karma.conf.js, then trace how the Firefox launcher handles the “failed 2 times (timeout)” path. Reproduce the Jenkins/Firefox timeout and verify that the npm/Karma process exits promptly with a failure instead of reaching the Java ProcessWatchDog timeout.

Written by the indexing model from the issue text.