diff --git a/lib/tests/run_tests.js b/lib/tests/run_tests.js
index 0c41d1e7e..4f4d521a6 100644
--- a/lib/tests/run_tests.js
+++ b/lib/tests/run_tests.js
@@ -1,80 +1,94 @@
+const async = require('async');
+const fs = require('fs-extra');
+const Mocha = require('mocha');
+const path = require('path');
+const Test = require('./test.js');
 const utils = require('../utils/utils.js');
 
-module.exports = {
-  run: function(filepath) {
-    const Mocha = require('mocha'),
-    fs = require('fs-extra'),
-    path = require('path');
-
-    const mocha = new Mocha();
-
-    if (filepath) {
-      if (filepath.substr(-1) === '/') {
-        // Add each .js file to the mocha instance
-        fs.readdirSync(filepath).filter(function(file){
-          // Only keep the .js files
-          // TODO: make this a configuration in embark.json
-          return file.substr(-3) === '.js';
-        }).forEach(function(file){
-          mocha.addFile(
-            path.join(filepath, file)
-          );
-        });
-      } else {
-        mocha.addFile(filepath);
-      }
-    } else {
-      var testDir = 'test/';
-
-      // Add each .js file to the mocha instance
-      fs.readdirSync(testDir).filter(function(file){
-        // Only keep the .js files
-        // TODO: make this a configuration in embark.json
-        return file.substr(-3) === '.js';
-      }).forEach(function(file){
-        mocha.addFile(
-          path.join(testDir, file)
-        );
-      });
+function getFilesFromDir(filePath, cb) {
+  fs.readdir(filePath, (err, files) => {
+    if (err) {
+      return cb(err);
     }
+    const testFiles = files.filter((file) => {
+      // Only keep the .js files
+      // TODO: make this a configuration in embark.json
+      return file.substr(-3) === '.js';
+    }).map((file) => {
+      return path.join(filePath, file);
+    });
+    cb(null, testFiles);
+  });
+}
 
-    let Test = require('./test.js');
-
-    global.assert = require('assert');
-
+module.exports = {
+  run: function(filePath) {
+    const mocha = new Mocha();
+    if (!filePath) {
+      filePath = 'test/';
+    }
     let configOptions = {
       gasPrice: 1
     };
-    global.config = function(config) {
-      configOptions = utils.recursiveMerge(configOptions, config);
-    };
-    // TODO: check how to pass the options
-    //global.EmbarkSpec = new Test(options);
 
-    // TODO: this global here might not be necessary at all
-    global.EmbarkSpec = new Test({});
-    global.web3 = global.EmbarkSpec.web3;
-
-    global.contract = function(describeName, callback) {
-      return Mocha.describe(describeName, callback);
-    };
-
-    // Run the tests.
-    let runner = mocha.run(function(failures) {
-      // Clean contracts folder for next test run
-      fs.remove('.embark/contracts', (_err) => {
-        process.on('exit', function () {
-          process.exit(failures);  // exit with non-zero status if there were failures
+    async.waterfall([
+      function getFiles(next) {
+        if (filePath.substr(-1) !== '/') {
+          mocha.addFile(filePath);
+          return next();
+        }
+        getFilesFromDir(filePath, (err, files) => {
+          if (err) {
+            console.error('Error while reading the directory');
+            return next(err);
+          }
+          files.forEach(file => {
+            mocha.addFile(file);
+          });
+          next();
         });
-        process.exit();
+      },
+      function setupGlobalNamespace(next) {
+        // ---------------- Deprecated code ------------------------------------------------------------
+        global.assert = require('assert');
+
+        global.config = function(config) {
+          configOptions = utils.recursiveMerge(configOptions, config);
+        };
+        // TODO: check how to pass the options
+        //global.EmbarkSpec = new Test(options);
+
+        // TODO: this global here might not be necessary at all
+        global.EmbarkSpec = new Test({});
+        global.web3 = global.EmbarkSpec.web3;
+
+        global.contract = function(describeName, callback) {
+          return Mocha.describe(describeName, callback);
+        };
+        next();
+        // ---------------- Deprecated code ------------------------------------------------------------
+      }
+    ], (err) => {
+      if (err) {
+        console.error(err);
+        process.exit(1);
+      }
+      // Run the tests.
+      let runner = mocha.run(function(failures) {
+        // Clean contracts folder for next test run
+        fs.remove('.embark/contracts', (_err) => {
+          process.on('exit', function () {
+            process.exit(failures);  // exit with non-zero status if there were failures
+          });
+          process.exit();
+        });
+      });
+
+      runner.on('suite', function() {
+        global.assert = require('assert');
+        global.EmbarkSpec = new Test({simulatorOptions: configOptions});
+        global.web3 = global.EmbarkSpec.web3;
       });
     });
-
-    runner.on('suite', function() {
-      global.assert = require('assert');
-      global.EmbarkSpec = new Test({simulatorOptions: configOptions});
-      global.web3 = global.EmbarkSpec.web3;
-    });
-
   }
 };