diff --git a/test/counter.test.js b/test/counter.test.js
index b6cc1648c..49a062263 100644
--- a/test/counter.test.js
+++ b/test/counter.test.js
@@ -4,3 +4,11 @@ const {counter} = require('./_30s.js');
 test('counter is a Function', () => {
   expect(counter).toBeInstanceOf(Function);
 });
+test('counter does not throw errors', () => {
+  expect(() => {
+    document.body.appendChild(document.createElement('div'));
+    counter('div', 1, 1000, 5, 2000);
+    counter('div', 1000, 1, 5, 2000);
+    counter('div', 1, 1000);
+  }).not.toThrow(TypeError);
+});
diff --git a/test/createEventHub.test.js b/test/createEventHub.test.js
index ca6ed2088..2b5f1e76e 100644
--- a/test/createEventHub.test.js
+++ b/test/createEventHub.test.js
@@ -4,3 +4,14 @@ const {createEventHub} = require('./_30s.js');
 test('createEventHub is a Function', () => {
   expect(createEventHub).toBeInstanceOf(Function);
 });
+test('createEventHub returns an object', () => {
+  let hub = createEventHub();
+  expect(typeof hub).toBe('object');
+  expect(typeof hub.hub).toBe('object');
+  expect(hub.emit).toBeInstanceOf(Function);
+  expect(hub.on).toBeInstanceOf(Function);
+  expect(hub.off).toBeInstanceOf(Function);
+  expect(hub.emit()).toBe(undefined);
+  expect(hub.on()).toBe(undefined);
+  expect(hub.off()).toBe(undefined);
+});