Fix error for modules parsed as scripts

lib/run-tests/index.js

@@ -92,9 +92,10 @@ function getExpected({ attrs }) {
 
 async function runTest(agent, test) {
   let { attrs, contents, file } = test;
+  const isModule = attrs.flags.module;
 
   try {
-    contents = transpile(contents, attrs.features);
+    contents = transpile(contents, attrs.features, isModule);
   } catch (error) {
     return { result: "parser error", error };
   }
@@ -146,9 +147,11 @@ class RethrownError extends ExtendedError {
     if (!error) throw new Error('RethrownError requires an error');
     this.original = error;
     this.new_stack = this.stack;
+    const errorStackString = error.stack && (typeof error.stack === 'string' ?
+      error.stack : error.stack.map(location => location.source).join('\n'));
     let message_lines = (this.message.match(/\n/g) || []).length + 1;
     this.stack = `${this.name}: ${this.message}\n${
       this.stack.split('\n').slice(0, message_lines + 1).join('\n')
-    }\n${error.stack.map(location => location.source).join('\n')}`;
+      }\n${errorStackString}`;
   }
 }

lib/run-tests/transpile.js

@@ -7,7 +7,7 @@ const getBabelPlugins = require("./get-babel-plugins");
 
 const configCaches = new Map();
 
-function getOptions(features) {
+function getOptions(features, isModule) {
   const featureKey = JSON.stringify(features);
   let config = configCaches.get(featureKey);
   if (config !== undefined) {
@@ -17,13 +17,13 @@ function getOptions(features) {
     configFile: false,
     presets: [[presetEnv, { spec: true }]],
     plugins: getBabelPlugins(features),
-    sourceType: "script",
+    sourceType: isModule ? "module" : "script",
   });
 
   configCaches.set(featureKey, config);
   return config;
 }
 
-module.exports = function transpile(code, features) {
-  return transformSync(code, getOptions(features)).code;
+module.exports = function transpile(code, features, isModule) {
+  return transformSync(code, getOptions(features, isModule)).code;
 };