Issue running karma task from gulp

I am trying to run karma tests from gulp task and I am getting this error:

Error: 1
   at formatError (C:\Users\Tim\AppData\Roaming\npm\node_modules\gulp\bin\gulp.js:161:10)
   at Gulp.<anonymous> (C:\Users\Tim\AppData\Roaming\npm\node_modules\gulp\bin\gulp.js:187:15)
   at Gulp.emit (events.js:95:17)
   at Gulp.Orchestrator._emitTaskDone (C:\path\to\project\node_modules\gulp\node_modules\orchestrator\index.js:264:8)
   at C:\path\to\project\node_modules\gulp\node_modules\orchestrator\index.js:275:23
   at finish (C:\path\to\project\node_modules\gulp\node_modules\orchestrator\lib\runTask.js:21:8)
   at cb (C:\path\to\project\node_modules\gulp\node_modules\orchestrator\lib\runTask.js:29:3)
   at removeAllListeners (C:\path\to\project\node_modules\karma\lib\server.js:216:7)
   at Server.<anonymous> (C:\path\to\project\node_modules\karma\lib\server.js:227:9)
   at Server.g (events.js:180:16)

My system is Windows 7, nodejs version is v0.10.32, gulp version:

[10:26:52] CLI version 3.8.8
[10:26:52] Local version 3.8.9

Also, the same error I am getting on Ubuntu 12.04 LTS while on newer Ubuntu (not sure what version) and mac os it is seems to be working ok. What can cause this error?

Update 5/11/2016: Before writing comment about the fact that accepted answer hide errors, please, see first two comments to that particular accepted answer. Use it only if know what you are doing. Related info: https://github.com/karma-runner/gulp-karma/pull/15

How are you running your tests with Gulp? I came up against this issue recently on OSX, running node v0.11.14 and gulp 3.8.10, whenever there were failing tests.

Changing from the recommended:

gulp.task('test', function(done) {
    karma.start({
        configFile: __dirname + '/karma.conf.js',
        singleRun: true
    }, done);
});

To:

gulp.task('test', function(done) {
    karma.start({
        configFile: __dirname + '/karma.conf.js',
        singleRun: true
    }, function() {
        done();
    });
});

...got rid of this error.

Seems to be down to how gulp handles error messages when an error is signalled in a callback. See Improve error messages on exit for more information.

None of these solutions worked correctly for me using gulp 3.9.1 and karma 1.1.1. Adding a reference to gulp-util npm install --save-dev gulp-util and updating the task to the below fix the error output very nicely, while maintaining exit status correctly.

var gutil = require('gulp-util');

gulp.task('test', function (done) {
  new Server({
    configFile: __dirname + '/karma.conf.js',
    singleRun: true
  }, function(err){
        if(err === 0){
            done();
        } else {
            done(new gutil.PluginError('karma', {
                message: 'Karma Tests failed'
            }));
        }
    }).start();
});

Below is a code snippet from gulp patterns on using Karma. It's a bit similar, but also uses the newer method how to start the karma.

/**
 * Start the tests using karma.
 * @param  {boolean} singleRun - True means run once and end (CI), or keep running (dev)
 * @param  {Function} done - Callback to fire when karma is done
 * @return {undefined}
 */
function startTests(singleRun, done) {
    var child;
    var excludeFiles = [];
    var fork = require('child_process').fork;
    var KarmaServer = require('karma').Server;
    var serverSpecs = config.serverIntegrationSpecs;

    if (args.startServers) {
        log('Starting servers');
        var savedEnv = process.env;
        savedEnv.NODE_ENV = 'dev';
        savedEnv.PORT = 8888;
        child = fork(config.nodeServer);
    } else {
        if (serverSpecs && serverSpecs.length) {
            excludeFiles = serverSpecs;
        }
    }

    var server = new KarmaServer({
        configFile: __dirname + '/karma.conf.js',
        exclude: excludeFiles,
        singleRun: singleRun
    }, karmaCompleted);
    server.start();

    ////////////////

    function karmaCompleted(karmaResult) {
        log('Karma completed');
        if (child) {
            log('shutting down the child process');
            child.kill();
        }
        if (karmaResult === 1) {
            done('karma: tests failed with code ' + karmaResult);
        } else {
            done();
        }
    }
}

What worked for me and gave a nice formatted error message is to provide an Error instance to the done callback.

gulp.task('test', function(done) {
    karma.start({
        configFile: __dirname + '/karma.conf.js',
        singleRun: true
    }, function(result) {
        if (result > 0) {
            return done(new Error(`Karma exited with status code ${result}`));
        }

        done();
    });
});

If you want to return with an error code, and want to see Karma's error output but not Gulp's (probably unrelated) stack trace:

gulp.task('test', function() {
    karma.start({
        configFile: __dirname + '/karma.conf.js',
        singleRun: true
    }, function(karmaExitStatus) {
           if (karmaExitStatus) {
               process.exit(1);
           }
    });
});

Not sure about Ubuntu, but I was getting a similar error on Windows, and installing one version back fixed it right away like this:

npm install -g gulp@3.8.8
npm install gulp@3.8.8

this is gulp's way of telling your tests have failed and that karma exited with a return code of 1. Why you would want to call done yourself and not pass the error as a message baffles me.

The right way to solve this according to Karma's documentation and https://github.com/pkozlowski-opensource, is to rely on Karma's watch mechanism rather than Gulp's:

gulp.task('tdd', function (done) {
  karma.start({
    configFile: __dirname + '/karma.conf.js'
  }, done);
});

Note the omission of singleRun: true.

@McDamon's workaround will work for gulp.watch, but you don't want to swallow exit codes like that when running on a CI server.

Gulp is also reworking how they handle exit codes in scenarios just like this one. See https://github.com/gulpjs/gulp/issues/71 and the other dozen or so related issues.

gulp.task('test', function(done) {
    karma.start({
        configFile: __dirname + '/karma.conf.js',
        singleRun: false 
    }, done);
});

passing singleRun: false argument will prevent the process from returning a value different of 0 (which would signify an error and exit gulp).

Run with singleRun: true if you only launching your test from a command line, not part of a continuous integration suite.

In case anyone else comes here, do not use the accepted solution. It will hide failed tests. If you need a quick solution to modify your gulp test task, you can use the solution found in this comment in this github thread.

gulp.src(src)
    // pipeline...
    .on('error', function (error) {
        console.error('' + error);
    });