Final result from http://willi.am/blog/2014/08/16/gulp-automation-path-abstraction/

gulpfile.js

var paths = require('./paths');

gulp.task('lint', function() {
    gulp.src(paths.app.concat(paths.test))
        .pipe(lint());
});

gulp.task('minify', function() {
    gulp.src(paths.app)
        .pipe(minify());
});

gulp.task('test', function() {
    gulp.src(paths.test)
        .pipe(test());
});

gulp.task('karma', function() {
    gulp.src(paths.karma)
        .pipe(karma({ configFile: 'karma.conf.js' }));
});

karma.conf.js

// karma.conf.js
var paths = require('./paths');

module.exports = function (config) {
    config.set({
        files: paths.karma,
        reporters: ['spec'],
        autoWatch: true,
        frameworks: ['jasmine'],
        browsers: ['PhantomJS'],
        plugins: [
            'karma-jasmine',
            'karma-spec-reporter',
            'karma-phantomjs-launcher'
        ],
    });
};

paths.js

var app = ['app/*.js'];
var test = ['test/*.js'];
var vendor = ['vendor/angular.js'];
module.exports = {
    app: app,
    test: test,
    vendor: vendor,
    karma: vendor.concat(app).concat(test)
};