diff --git a/scripts/mocha.js b/scripts/mocha.js
index 36b9c92a8df3e02..38a977af3e78673 100644
--- a/scripts/mocha.js
+++ b/scripts/mocha.js
@@ -1 +1,2 @@
-require('mocha/bin/mocha');
+require('../src/optimize/babel/register');
+require('../test/scripts/run_mocha');
diff --git a/test/scripts/run_mocha.js b/test/scripts/run_mocha.js
new file mode 100644
index 000000000000000..e5c747e2573d1d6
--- /dev/null
+++ b/test/scripts/run_mocha.js
@@ -0,0 +1,16 @@
+const debugInBand = process.execArgv.some(arg => {
+  switch (arg) {
+    case '--debug':
+    case '--debug-brk':
+    case '-d':
+    case '--inspect':
+      return true;
+  }
+});
+
+if (debugInBand) {
+  process.argv.push('--no-timeouts');
+  require('mocha/bin/_mocha');
+} else {
+  require('mocha/bin/mocha');
+}