How to get Mocha to display the correct line numbers in the source files if the test fails?

Question

I use Mocha for my NodeJS tests, and when the test failed due to an error generated by my source code (for example, " TypeError: Cannot read property 'prop' of null "), the line numbers in the displayed stacktrace are wrong (they don’t "t match the original source file, but much more).

  1) MyApp should do something: TypeError: Cannot read property 'prop' of null at MyApp.<anonymous> (/path/to/my-project/lib/my-project.js:515:93) at MyApp.build (/path/to/my-project/lib/my-project.js:774:16) at Context.<anonymous> (/path/to/my-project/test/test.js:62:67) at Test.Runnable.run (/path/to/my-project/node_modules/mocha/lib/runnable.js:216:15) at Runner.runTest (/path/to/my-project/node_modules/mocha/lib/runner.js:373:10) at /path/to/my-project/node_modules/mocha/lib/runner.js:451:12 at next (/path/to/my-project/node_modules/mocha/lib/runner.js:298:14) at /path/to/my-project/node_modules/mocha/lib/runner.js:308:7 at next (/path/to/my-project/node_modules/mocha/lib/runner.js:246:23) at Object._onImmediate (/path/to/my-project/node_modules/mocha/lib/runner.js:275:5) at processImmediate [as _immediateCallback] (timers.js:330:15) 

(Here my-project.js has only 279 lines!)

Is there any way to tell Mocha to display them correctly?

Answer 1

This happens when the code is controlled by a coverage tool (e.g. blanket , istanbul , etc.). Double check to make sure you are not loading it into your regular tests by mistake.