formatError cannot filter out stacktrace lines as stated

[levithomason]

Expected behaviour

Per the docs for formatError I expect to be able to:

Format assertion errors and stack traces. Useful for removing vendors and compiled sources.

Actual behaviour

No matter the return value, a new line is always appended to the formatError return value. This makes it impossible to remove the line from the stack. There are always the same number of lines, even if they are empty.

Environment Details

• Karma version: 1.5.0

• Relevant part of your karma.config.js file:

  formatError(msg) {
    return ''
  }

Steps to reproduce the behaviour

1. Create a basic karma config.
2. Add an formatError config function that returns an empty string.
3. Write a failing test
4. Note a new line is appended to every original line in the error message, making it impossible to trim the number of lines in a stack trace.