Add unit tests for commit SHA

__tests__/create-branch.test.ts

@@ -1,38 +1,27 @@
-import {createBranch} from '../src/create-branch'
+import { createBranch } from '../src/create-branch'
 import { readFileSync } from 'fs';
 import { context } from '@actions/github';
 
 describe('Create a branch based on the input', () => {
+  process.env.GITHUB_TOKEN = 'token'
 
-  let githubMock;
-  let contextMock;
   let branch = 'release-v1';
-  let octokitMock;
-
-  beforeEach(()=> {
-    octokitMock = {
-      git: {
-        createRef: jest.fn()
-      },
-      repos: {
-        getBranch: jest.fn()
-      }
+  let sha = 'ffac537e6cbbf934b08745a378932722df287a53';
+  let contextMock = JSON.parse(readFileSync('__tests__/context.json', 'utf8'));
+  let githubMock = jest.fn();
+  let octokitMock = {
+    git: {
+      createRef: jest.fn()
+    },
+    repos: {
+      getBranch: jest.fn()
     }
-  })
-
-  beforeEach(()=> {
-    githubMock = jest.fn().mockImplementation(() => {
-      return octokitMock;
-    })
-  })
+  };
 
   beforeEach(() => {
-    contextMock = JSON.parse(readFileSync('__tests__/context.json', 'utf8'))
-  })
-
-  beforeEach(() => {
-    process.env.GITHUB_TOKEN = 'token'
-  })
+    jest.resetAllMocks();
+    githubMock.mockImplementation(() => octokitMock);
+  });
 
   it('gets a branch', async () => {
     octokitMock.repos.getBranch.mockRejectedValue(new HttpError())
@@ -43,10 +32,9 @@ describe('Create a branch based on the input', () => {
       owner: 'peterjgrainger',
       branch
     })
-  })
-
+  });
 
-  it('Create new branch if not already there', async () => {
+  it('Creates a new branch if not already there', async () => {
     octokitMock.repos.getBranch.mockRejectedValue(new HttpError())
     await createBranch(githubMock, contextMock, branch)
     expect(octokitMock.git.createRef).toHaveBeenCalledWith({
@@ -55,6 +43,15 @@ describe('Create a branch based on the input', () => {
     })
   });
 
+  it('Creates a new branch from a given commit SHA', async () => {
+    octokitMock.repos.getBranch.mockRejectedValue(new HttpError())
+    await createBranch(githubMock, contextMock, branch, sha)
+    expect(octokitMock.git.createRef).toHaveBeenCalledWith({
+      ref: 'refs/heads/release-v1',
+      sha: 'ffac537e6cbbf934b08745a378932722df287a53'
+    })
+  })
+
   it('Replaces refs/heads in branch name', async () => {
     octokitMock.repos.getBranch.mockRejectedValue(new HttpError())
     await createBranch(githubMock, contextMock, `refs/heads/${branch}`)
@@ -64,15 +61,15 @@ describe('Create a branch based on the input', () => {
     })
   });
 
-  it('fails if github token isn\'t defined', async() => {
+  it('Fails if github token isn\'t defined', async () => {
     delete process.env.GITHUB_TOKEN
     expect.assertions(1);
     try {
       await createBranch(githubMock, contextMock, branch)
     } catch (error) {
       expect(error).toEqual(new ReferenceError('No token defined in the environment variables'))
     }
-  })
+  });
 });
 
 class HttpError extends Error {