refactor: several improvements (#262)

- more tests
- file read in config
- reduce if depth
- reduce unnecessary requests

__tests__/assets/result

@@ -0,0 +1 @@
+hi there

__tests__/config.test.ts

@@ -1,18 +1,127 @@
-import * as process from 'process'
-
-test('test runs', () => {
-  process.env['INPUT_HEADER'] = ''
+beforeEach(() => {
+  process.env['GITHUB_REPOSITORY'] = 'marocchino/stick-pull-request-comment'
   process.env['INPUT_NUMBER'] = '123'
   process.env['INPUT_APPEND'] = 'false'
   process.env['INPUT_RECREATE'] = 'false'
   process.env['INPUT_DELETE'] = 'false'
   process.env['INPUT_GITHUB_TOKEN'] = 'some-token'
-  process.env['GITHUB_REPOSITORY'] = 'marocchino/stick-pull-request-comment'
+})
+
+afterEach(() => {
+  jest.resetModules()
+  delete process.env['GITHUB_REPOSITORY']
+  delete process.env['INPUT_REPO']
+  delete process.env['INPUT_HEADER']
+  delete process.env['INPUT_MESSAGE']
+  delete process.env['INPUT_NUMBER']
+  delete process.env['INPUT_APPEND']
+  delete process.env['INPUT_RECREATE']
+  delete process.env['INPUT_DELETE']
+  delete process.env['INPUT_GITHUB_TOKEN']
+  delete process.env['INPUT_PATH']
+})
+
+test('repo', () => {
+  process.env['INPUT_REPO'] = 'other'
   expect(require('../src/config')).toMatchObject({
     pullRequestNumber: expect.any(Number),
-    repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
-    message: '',
-    path: '',
+    repo: {owner: 'marocchino', repo: 'other'},
+    body: '',
+    header: '',
+    append: false,
+    recreate: false,
+    deleteOldComment: false,
+    githubToken: 'some-token'
+  })
+})
+test('header', () => {
+  process.env['INPUT_HEADER'] = 'header'
+  expect(require('../src/config')).toMatchObject({
+    pullRequestNumber: expect.any(Number),
+    repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+    body: '',
+    header: 'header',
+    append: false,
+    recreate: false,
+    deleteOldComment: false,
+    githubToken: 'some-token'
+  })
+})
+test('append', () => {
+  process.env['INPUT_APPEND'] = 'true'
+  expect(require('../src/config')).toMatchObject({
+    pullRequestNumber: expect.any(Number),
+    repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+    body: '',
+    header: '',
+    append: true,
+    recreate: false,
+    deleteOldComment: false,
+    githubToken: 'some-token'
+  })
+})
+test('recreate', () => {
+  process.env['INPUT_RECREATE'] = 'true'
+  expect(require('../src/config')).toMatchObject({
+    pullRequestNumber: expect.any(Number),
+    repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+    body: '',
+    header: '',
+    append: false,
+    recreate: true,
+    deleteOldComment: false,
+    githubToken: 'some-token'
+  })
+})
+test('delete', () => {
+  process.env['INPUT_DELETE'] = 'true'
+  expect(require('../src/config')).toMatchObject({
+    pullRequestNumber: expect.any(Number),
+    repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+    body: '',
+    header: '',
+    append: false,
+    recreate: false,
+    deleteOldComment: true,
+    githubToken: 'some-token'
+  })
+})
+describe('path', () => {
+  test('when exists return content of a file', () => {
+    process.env['INPUT_PATH'] = './__tests__/assets/result'
+    expect(require('../src/config')).toMatchObject({
+      pullRequestNumber: expect.any(Number),
+      repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+      body: 'hi there\n',
+      header: '',
+      append: false,
+      recreate: false,
+      deleteOldComment: false,
+      githubToken: 'some-token'
+    })
+  })
+
+  test('when not exists return null string', () => {
+    process.env['INPUT_PATH'] = './__tests__/assets/not_exists'
+    expect(require('../src/config')).toMatchObject({
+      pullRequestNumber: expect.any(Number),
+      repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+      body: '',
+      header: '',
+      append: false,
+      recreate: false,
+      deleteOldComment: false,
+      githubToken: 'some-token'
+    })
+  })
+})
+
+test('message', () => {
+  process.env['INPUT_MESSAGE'] = 'hello there'
+  expect(require('../src/config')).toMatchObject({
+    pullRequestNumber: expect.any(Number),
+    repo: {owner: 'marocchino', repo: 'stick-pull-request-comment'},
+    body: 'hello there',
     header: '',
     append: false,
     recreate: false,