[test] Catch error between tests

The issue was found in mui/mui-x#543.
I also create a new setupKarma.js file so the X repo can import it directly.

test/karma.tests.js

@@ -1,32 +1,5 @@
-/* eslint-env mocha */
 import './utils/init';
-import { createMochaHooks } from './utils/mochaHooks';
-
-const mochaHooks = createMochaHooks(window.Mocha);
-
-before(function beforeAllHook() {
-  mochaHooks.beforeAll.forEach((mochaHook) => {
-    mochaHook.call(this);
-  });
-});
-
-after(function afterAllHook() {
-  mochaHooks.afterAll.forEach((mochaHook) => {
-    mochaHook.call(this);
-  });
-});
-
-beforeEach(function beforeEachHook() {
-  mochaHooks.beforeEach.forEach((mochaHook) => {
-    mochaHook.call(this);
-  });
-});
-
-afterEach(function afterEachHook() {
-  mochaHooks.afterEach.forEach((mochaHook) => {
-    mochaHook.call(this);
-  });
-});
+import './utils/setupKarma';
 
 const integrationContext = require.context(
   '../packages/material-ui/test/integration',

test/utils/setupKarma.js

@@ -0,0 +1,51 @@
+/* eslint-env mocha */
+import { createMochaHooks } from './mochaHooks';
+
+const mochaHooks = createMochaHooks(window.Mocha);
+
+before(function beforeAllHook() {
+  mochaHooks.beforeAll.forEach((mochaHook) => {
+    mochaHook.call(this);
+  });
+});
+
+after(function afterAllHook() {
+  mochaHooks.afterAll.forEach((mochaHook) => {
+    mochaHook.call(this);
+  });
+});
+
+beforeEach(function beforeEachHook() {
+  mochaHooks.beforeEach.forEach((mochaHook) => {
+    mochaHook.call(this);
+  });
+});
+
+afterEach(function afterEachHook() {
+  mochaHooks.afterEach.forEach((mochaHook) => {
+    mochaHook.call(this);
+  });
+});
+
+// Ensure that uncaught exceptions between tests result in the tests failing.
+// This works around an issue with mocha / karma-mocha, see
+// https://github.com/karma-runner/karma-mocha/issues/227
+let pendingError = null;
+let pendingErrorNotice = null;
+
+window.addEventListener('error', (event) => {
+  pendingError = event.error;
+  pendingErrorNotice = 'An uncaught exception was thrown between tests';
+});
+
+window.addEventListener('unhandledrejection', (event) => {
+  pendingError = event.reason;
+  pendingErrorNotice = 'An uncaught promise rejection occurred between tests';
+});
+
+afterEach(() => {
+  if (pendingError) {
+    console.error(pendingErrorNotice);
+    throw pendingError;
+  }
+});