Below is a task I was able to build that seems to solve the problem. Basically I use an outside library to gather the files names as an array. And then pass that array as the entry points
'use strict;'
var config = require('../config');
var gulp = require('gulp');
var plumber = require('gulp-plumber');
var glob = require('glob');
var browserify = require('browserify');
var source = require('vinyl-source-stream');
gulp.task('tests', function(){
var testFiles = glob.sync('./spec/**/*.js');
return browserify({
entries: testFiles,
extensions: ['.jsx']
})
.bundle({debug: true})
.pipe(source('app.js'))
.pipe(plumber())
.pipe(gulp.dest(config.dest.development));
});