adding unit test for pub-sub.js

Author: dev-javascript

src/utils/api/pub-sub.test.js

@@ -0,0 +1,29 @@
+import Pub_Sub from './pub_sub.js';
+let instance = null;
+beforeEach(() => {
+  instance = new Pub_Sub();
+});
+afterEach(() => {
+  instance = null;
+});
+describe('Pub_Sub.prototype.on :  ', () => {
+  test('it can attach diferent event handlers function for one event', () => {
+    expect(instance._publishers.onSelect.length).toBe(0);
+    instance.on('onSelect', () => {});
+    instance.on('onSelect', () => {});
+    expect(instance._publishers.onSelect.length).toBe(2);
+  });
+  test('it does not attach an event handler twice', () => {
+    expect(instance._publishers.onSelect.length).toBe(0);
+    const onSelectHandler = () => {};
+    instance.on('onSelect', onSelectHandler);
+    instance.on('onSelect', onSelectHandler);
+    expect(instance._publishers.onSelect.length).toBe(1);
+  });
+  test('it can not attach an event handler for beforeSelect or beforeClose event', () => {
+    instance.on('beforeSelect', () => {});
+    instance.on('beforeClose', () => {});
+    expect(typeof instance._publishers.beforeSelect).toBe('undefined');
+    expect(typeof instance._publishers.beforeClose).toBe('undefined');
+  });
+});