browserNoActivityTimeout Configuration for Slow CI Environments

Answer the question first

To balance CI stability with rapid stall detection, measure the longest legitimate idle period in your CI run and set browserNoActivityTimeout to a value safely above that (e.g., 1.5–2× the observed maximum). This keeps the timeout low enough to catch true hangs while avoiding false failures caused by slow bundling or test execution.

Steps to tune the global timeout

1. Run a representative CI build with logging enabled to capture the longest period where the browser shows no activity.

   karma start --log-level debug 2> ci-run.log
   

2. Inspect the log for timestamps between the last activity message and the next activity or disconnect. Identify the maximum gap (in milliseconds).

3. Choose a timeout value: timeout = maxGap * 1.5 (round up to a convenient number, e.g., 60000 ms).

4. Edit karma.conf.js and set the value:

   module.exports = function(config) {
     config.set({
       // … other settings
       browserNoActivityTimeout: 60000, // 60 seconds example
     });
   };
   

5. Verify the setting takes effect:

   grep browserNoActivityTimeout karma.conf.js
   

6. Run a test suite that includes a known long‑running test; ensure Karma waits the configured interval before disconnecting (check debug logs for the "No activity" message).

Per‑suite timeout availability

Karma does not provide a built‑in mechanism to apply different browserNoActivityTimeout values to individual test suites or files within a single configuration. The timeout is global to the runner.

If you need distinct timeouts for subsets of tests, the documented approach is to run separate Karma instances (or use karma-parallel) each with its own karma.conf.js that specifies the appropriate timeout for that subset.

When to ask for more detail

If your CI environment exhibits highly variable idle periods (e.g., some test suites regularly exceed 2× the measured maximum while others stay well below), sharing the observed distribution of idle gaps would help refine the multiplier or decide whether to split the suite into multiple Karma runs.