ensure invalid arguments are not ignored when using bin/mocha; closes #…

…3687

Signed-off-by: Christopher Hiller <boneskull@boneskull.com>

test/integration/invalid-arguments.spec.js

@@ -0,0 +1,20 @@
+'use strict';
+
+var invokeMocha = require('./helpers').invokeMocha;
+
+describe('invalid arguments', function() {
+  it('should exit with failure if arguments are invalid', function(done) {
+    invokeMocha(
+      ['--ui'],
+      function(err, result) {
+        if (err) {
+          return done(err);
+        }
+        expect(result, 'to have failed');
+        expect(result.output, 'to match', /not enough arguments/i);
+        done();
+      },
+      {stdio: 'pipe'}
+    );
+  });
+});