test: test the alerts module

Check that alerts can be registered and displayed via the
alerts module

test/alerts.test.js

@@ -0,0 +1,40 @@
+var test = require('tap-only');
+var testUtils = require('./utils');
+var alerts = require('../lib/alerts');
+
+var exampleAlert = function (id, type) {
+  type = type || 'info';
+  return {
+    msg: 'Example alert ' + id,
+    type: type,
+  };
+}
+
+test('register an alert', function (t) {
+  t.plan(1);
+
+  alerts.registerAlerts([ exampleAlert(1) ]);
+  t.equal(alerts.displayAlerts().trim(), exampleAlert(1).msg,
+    'alert is displayed');
+});
+
+test('register the same alert multiple times', function (t) {
+  t.plan(1);
+
+  alerts.registerAlerts([ exampleAlert(1) ]);
+  alerts.registerAlerts([ exampleAlert(1) ]);
+  t.equal(alerts.displayAlerts().trim(), exampleAlert(1).msg,
+    'alert is only displayed once');
+});
+
+test('register two different alerts', function (t) {
+  t.plan(2);
+
+  alerts.registerAlerts([ exampleAlert(1) ]);
+  alerts.registerAlerts([ exampleAlert(2) ]);
+  const displayedAlerts = alerts.displayAlerts();
+  t.contains(displayedAlerts, exampleAlert(1).msg,
+    'first alert is displayed');
+  t.contains(displayedAlerts, exampleAlert(2).msg,
+    'second alert is displayed');
+});