Use separate config file for renderer tests

.mocharc.renderer.json

@@ -0,0 +1,9 @@
+{
+  "renderer": true,
+  "color": true,
+  "window-config-file": "test/support/window.config.json",
+  "script": [
+    "test/support/preload.js"
+  ],
+  "url": "test/support/index.html"
+}

lib/main.js

@@ -29,7 +29,7 @@ exports.main = (argv = process.argv.slice(2)) => {
     .fail((msg, err, yargs) => {
       yargs.showHelp()
       console.error(`\n${symbols.error} ${ansi.red('ERROR:')} ${msg}`)
-      console.error(err.stack)
+      if (err) console.error(err.stack)
       app.exit(1)
     })
     .help('help', 'Show usage information and exit')

package.json

@@ -7,10 +7,19 @@
     "pretest": "standard",
     "test": "npm run test:main && npm run test:renderer",
     "test:main": "node bin/electron-mocha test/main",
-    "test:renderer": "node bin/electron-mocha --renderer --script test/support/preload.js --url test/support/index.html test/renderer",
+    "test:renderer": "node bin/electron-mocha --config .mocharc.renderer.json test/renderer",
     "mocha": "node bin/electron-mocha",
     "prepublishOnly": "npm test"
   },
+  "mocha": {
+    "color": true,
+    "require-main": [
+      "test/support/requireMain"
+    ],
+    "require": [
+      "test/support/require"
+    ]
+  },
   "bin": {
     "electron-mocha": "./bin/electron-mocha"
   },