Added test for Counter Container

Author: dolfolife

src/Hello/containers/Counter.tsx

@@ -12,8 +12,8 @@ const Counter = (props: IProps) => {
     return (
         <div>
             <p>Counter: {counter}</p>
-            <button onClick={increment} label="Increment" />
-            <button onClick={decrement} label="Decrement" />
+            <button onClick={increment} label="Increment" id="increment"/>
+            <button onClick={decrement} label="Decrement" id="decrement"/>
         </div>
     );
 };

src/Hello/containers/__test__/Counter.test.tsx

@@ -0,0 +1,31 @@
+import * as React from "react";
+import {shallow} from "enzyme";
+
+import Counter from "../Counter";
+
+describe("counter container", () => {
+    let subject: any,
+        mockIncrement: () => {},
+        mockDecrement: () => {};
+    beforeEach(() => {
+        mockIncrement = jest.fn();
+        mockDecrement = jest.fn();
+        subject = shallow(<Counter increment={mockIncrement} decrement={mockDecrement} counter={1}/>);
+    });
+
+    it("it shows the counter", () => {
+        expect(subject.text()).toContain("1");
+    });
+
+    it("clicking on the increment button call property increment", () => {
+        subject.find("#increment").props().onClick();
+
+        expect(mockIncrement).toBeCalled();
+    });
+
+    it("clicking on the decrement button call property decrement", () => {
+        subject.find("#decrement").props().onClick();
+
+        expect(mockDecrement).toBeCalled();
+    });
+});