added tests for BackgroundPanel

addons/background/src/__tests__/index.tsx

@@ -0,0 +1,59 @@
+import * as React from "react"; // tslint:disable-line
+const EventEmitter = require("events"); // tslint:disable-line
+import { shallow } from "enzyme";
+import { BackgroundDecorator } from "../index";
+const TestUtils = require("react-addons-test-utils"); // tslint:disable-line
+
+const testStory = () => () => <p>Hello World!</p>;
+
+describe("Background Decorator", () => {
+  it("should exist", () => {
+    const SpiedChannel = new EventEmitter();
+    const backgroundDecorator = shallow(<BackgroundDecorator story={testStory} channel={SpiedChannel} />);
+    expect(backgroundDecorator).toBeDefined();
+  });
+
+  it("should initially have a transparent background state", () => {
+    const SpiedChannel = new EventEmitter();
+    const backgroundDecorator = shallow(<BackgroundDecorator story={testStory} channel={SpiedChannel} />);
+
+    expect(backgroundDecorator.state().background).toBe("transparent");
+  });
+
+  it("should have a background matching its state", () => {
+    const SpiedChannel = new EventEmitter();
+    const backgroundDecorator = shallow(<BackgroundDecorator story={testStory} channel={SpiedChannel} />);
+
+    expect(backgroundDecorator.html().match(/background-color:transparent/gmi).length).toBe(1);
+  });
+
+  it("should set internal state when background event called", () => {
+    const SpiedChannel = new EventEmitter();
+    const backgroundDecorator = shallow(<BackgroundDecorator story={testStory} channel={SpiedChannel} />);
+
+    SpiedChannel.emit("background", "#123456");
+    expect(backgroundDecorator.state().background).toBe("#123456");
+  });
+
+  it("should send background-unset event when the component unmounts", () => {
+    const SpiedChannel = new EventEmitter();
+    const backgroundDecorator = shallow(<BackgroundDecorator story={testStory} channel={SpiedChannel} />);
+
+    const spy = jest.fn();
+    SpiedChannel.on('background-unset', spy);
+
+    backgroundDecorator.unmount();
+
+    expect(spy).toBeCalled();
+  });
+
+  it("should send background-set event when the component mounts", () => {
+    const SpiedChannel = new EventEmitter();
+    const spy = jest.fn();
+    SpiedChannel.on('background-set', spy);
+
+    const backgroundDecorator = shallow(<BackgroundDecorator story={testStory} channel={SpiedChannel} />);
+
+    expect(spy).toBeCalled();
+  });
+});

addons/background/src/index.tsx

@@ -26,7 +26,13 @@ export class BackgroundDecorator extends React.Component<any, any> {
   constructor(props) {
     super(props);
 
-    this.channel = addons.getChannel();
+    // A channel is explicitly passed in for testing
+    if (this.props.channel) {
+      this.channel = this.props.channel;
+    } else {
+      this.channel = addons.getChannel();
+    }
+
     this.story = this.props.story();
   }