How to debug Mocha tests?

[MarkHerhold]

I cannot get iron-node to work with mocha. I have seen and read the page on "How to debug other Node.js command line applications like a Grunt task?" but that did not help.

I am able to debug things running in mocha just fine with node-inspector using:

node-debug ./node_modules/mocha/bin/_mocha ./spec/mytest.spec.js

I have tried the same thing with iron-node along with passing in different arguments.

This works, but the tests all run and don't trigger the debugger.

iron-node ./node_modules/mocha/bin/_mocha -- ./spec/mytest.spec.js

I am using the latest version of iron-node and mocha.
Environment: iojs 3.2.0, Ubuntu 15

[s-a]

Have you tried the keyword debugger;? There is also a doc.https://github.com/s-a/iron-node/blob/master/docs/MASTER-THE-BREAKPOINTS.md which might be interesting.

[MarkHerhold]

Sorry, yes I have tried the debugger; statement. I am not sure the source even gets loaded so I don't think I can set a breakpoint.

[s-a]

Hmm, yes mocha spawns another process where it does not work anymore.

I am not sure why people decide to use such a strategy. However to make it work we need to create an alias and change the call to iron-node instead of node

alias for shell (on windows):

# locate 
$ where mocha;
# --> C:\Users\Stephan\AppData\Roaming\npm\mocha.cmd

alias file one:

$ cp c:\Users\Stephan\AppData\Roaming\npm\mocha.cmd c:\Users\Stephan\AppData\Roaming\npm\iron-mocha.cmd;

edit iron-mocha.cmd

:: Created by npm, please don't edit manually.
@IF EXIST "%~dp0\node.exe" (
  "%~dp0\node.exe"  "%~dp0\node_modules\mocha\bin\iron-mocha" %*
) ELSE (
  node  "%~dp0\node_modules\mocha\bin\iron-mocha" %*
)

alias file two:

$ cp c:\Users\Stephan\AppData\Roaming\npm\node_modules\mocha\bin\mocha c:\Users\Stephan\AppData\Roaming\npm\node_modules\mocha\bin\iron-mocha;

edit iron-mocha: and add process.argv[0] = "iron-node.cmd";

# c:\Users\Stephan\AppData\Roaming\npm\node_modules\mocha\bin\iron-mocha:
#!/usr/bin/env node

/**
 * This tiny wrapper file checks for known node flags and appends them
 * when found, before invoking the "real" _mocha(1) executable.
 */

var spawn = require('child_process').spawn
  , args = [ __dirname + '/_mocha' ];

process.argv.slice(2).forEach(function (arg) {
  switch (arg) {
    case '-d':
      args.unshift('--debug');
      break;
    case 'debug':
    case '--debug':
    case '--debug-brk':
      args.unshift(arg);
      break;
    case '-gc':
    case '--expose-gc':
      args.unshift('--expose-gc');
      break;
    case '--gc-global':
    case '--harmony':
    case '--harmony-proxies':
    case '--harmony-collections':
      args.unshift(arg);
      break;
    default:
      if (0 == arg.indexOf('--trace')) args.unshift(arg);
      else args.push(arg);
      break;
  }
});

process.argv[0] = "iron-node.cmd";
var proc = spawn(process.argv[0], args, { customFds: [0,1,2] });
proc.on('exit', function (code, signal) {
  process.on('exit', function(){
    if (signal) {
      process.kill(process.pid, signal);
    } else {
      process.exit(code);
    }
  });
});

done

$ cd your-projectfolder;
$ iron-mocha; # instead of mocha

[s-a]

OSOBLETE! Thanks to @michael-brade #73 (comment) we have now a very smarter way to debug Mocha!

Please refer to https://github.com/s-a/iron-node/blob/master/docs/DEBUG-NODEJS-COMMANDLINE-APPS.md for forthcoming updates.