refactor(index.ts): updates index to use instance an of a GitHub class

- Updates `fetchRecentlyClosedPullRequests` in `index` to use the new
version of `GitHub` that requires creating an instance that is passed in
the auth token.
- Updates `fetchRecentlyClosedPullRequests` to require an `auth_token`
is passed in
- Updates tests for `fetchRecentlyClosedPullRequests` to use different
jest mocking functionality and mock out the implementation of `GitHub`.
Now, instead of passing in a fake module that matches `GitHub` we use
magic jest mocking to create a mocked GitHub import which lets us mock
the constructor.

BREAKING CHANGE: Updates the function `fetchRecentlyClosedPullRequests`
exported from `index.ts` to now take in the auth token. This allows for
more flexibilty in that the auth token no longer **has** to be fetched
from an environment variable named `GIT

Author: tmr08c

src/github.ts

@@ -73,7 +73,7 @@ interface IGitHubGraphqlArgs {
 }
 
 export class GitHub {
-  token: string;
+  private token: string;
 
   constructor({ authToken }: { authToken: string }) {
     this.token = authToken;

src/index.test.ts

@@ -4,21 +4,24 @@ import { fetchRecentlyClosedPullRequests } from "./index";
 // Reset Date back to the real date
 afterEach(() => MockDate.reset());
 
-class FakeService {
-  public static async recentlyClosedPullRequests(): Promise<any> {
-    return {};
-  }
-  public static __searchQueryString(): string {
-    return "";
-  }
-}
-
-const fakeApiCall = (FakeService.recentlyClosedPullRequests = jest.fn());
-
 test("dates default to the last week", () => {
   MockDate.set("1/8/2019");
 
-  fetchRecentlyClosedPullRequests({ organization: "my-org" }, FakeService);
+  jest.mock("./github");
+  const MockedGitHub = require("./github").GitHub;
+
+  const fakeApiCall = jest.fn().mockImplementation();
+  MockedGitHub.mockImplementation(() => {
+    return {
+      recentlyClosedPullRequests: fakeApiCall
+    };
+  });
+
+  fetchRecentlyClosedPullRequests(
+    { organization: "my-org" },
+    "fake-token",
+    MockedGitHub
+  );
 
   expect(fakeApiCall).toHaveBeenCalledWith({
     endDate: new Date("1/7/2019"),

src/index.ts

@@ -7,7 +7,8 @@ interface IRequestParams {
 
 export function fetchRecentlyClosedPullRequests(
   requestParams: IRequestParams,
-  service = GitHub
+  authToken: string,
+  Service = GitHub
 ) {
   const dates = {
     endDate: subDays(new Date(), 1),
@@ -21,5 +22,5 @@ export function fetchRecentlyClosedPullRequests(
     } that were closed between ${dates.startDate} and ${dates.endDate}`
   );
 
-  return service.recentlyClosedPullRequests(args);
+  return new Service({ authToken }).recentlyClosedPullRequests(args);
 }