feat: Create first service (browser)

Implement a simple infrastructure with a single service and method

src/__tests__/container-service.test.ts

@@ -0,0 +1,46 @@
+import ContainerService from '../container-service'
+import { IContainerService } from '../services'
+
+const createMockService = (applies: boolean, start: () => void): IContainerService => ({
+  applies: () => applies,
+  start,
+})
+
+describe('Container Service', () => {
+  const service1Applies = false
+  const service1Start = jest.fn()
+  const mockService1 = createMockService(service1Applies, service1Start)
+
+  const service2Applies = true
+  const service2Start = jest.fn()
+  const mockService2 = createMockService(service2Applies, service2Start)
+
+  beforeEach(() => {
+    service1Start.mockReset()
+    service2Start.mockReset()
+  })
+
+  it('selects the first strategy that applies (1)', () => {
+    const containerService = new ContainerService([mockService1, mockService2])
+    containerService.start()
+
+    expect(service1Start).toHaveBeenCalledTimes(0)
+    expect(service2Start).toHaveBeenCalledTimes(1)
+  })
+
+  it('selects the first strategy that applies (2)', () => {
+    const containerService = new ContainerService([mockService2, mockService1])
+    containerService.start()
+
+    expect(service1Start).toHaveBeenCalledTimes(0)
+    expect(service2Start).toHaveBeenCalledTimes(1)
+  })
+
+  it('start calls start on the service', () => {
+    const containerService = new ContainerService([mockService2])
+    expect(service2Start).toHaveBeenCalledTimes(0)
+
+    containerService.start()
+    expect(service2Start).toHaveBeenCalledTimes(1)
+  })
+})

src/__tests__/index.test.ts

@@ -1,7 +1,10 @@
+import services from '../services'
+import ContainerService from '../container-service'
+
 import containerService from '../index'
 
 describe('containerService', () => {
-  it('has a double function', () => {
-    expect(containerService.double(5)).toBe(10)
+  it('is constructed with the services', () => {
+    expect(containerService).toEqual(new ContainerService(services))
   })
 })

src/container-service.ts

@@ -0,0 +1,15 @@
+import { IContainerService } from './services'
+
+class ContainerService {
+  private service: IContainerService
+
+  constructor(services: IContainerService[]) {
+    this.service = services.find(s => s.applies())
+  }
+
+  public start() {
+    this.service.start()
+  }
+}
+
+export default ContainerService

src/index.ts

@@ -1,5 +1,4 @@
-const containerService = {
-  double: (input: number) => input * 2,
-}
+import services from './services'
+import ContainerService from './container-service'
 
-export default containerService
+export default new ContainerService(services)

src/services/__tests__/browser-service.test.ts

@@ -0,0 +1,13 @@
+import BrowserService from '../browser-service'
+
+const browserService = new BrowserService()
+
+describe('BrowserService', () => {
+  it('applies returns true', () => {
+    expect(browserService.applies()).toBe(true)
+  })
+
+  it('start does not throw an error', () => {
+    browserService.start()
+  })
+})

src/services/__tests__/services.test.ts

@@ -0,0 +1,12 @@
+const mockBrowserService = class {}
+jest.mock('../browser-service', () => ({
+  default: mockBrowserService,
+}))
+
+import services from '../services'
+
+describe('services', () => {
+  it('combines all the services in the correct order', () => {
+    expect(services).toEqual([new mockBrowserService()])
+  })
+})

src/services/browser-service.ts

@@ -0,0 +1,13 @@
+import IContainerService from './container-service'
+
+class BrowserService implements IContainerService {
+  public applies() {
+    return true
+  }
+
+  public start() {
+    // No-op
+  }
+}
+
+export default BrowserService

src/services/container-service.ts

@@ -0,0 +1,6 @@
+interface IContainerService {
+  applies(): boolean
+  start(): void
+}
+
+export default IContainerService

src/services/index.ts

@@ -0,0 +1,6 @@
+import IContainerService from './container-service'
+
+import services from './services'
+
+export default services
+export { IContainerService }

src/services/services.ts

@@ -0,0 +1,7 @@
+import BrowserService from './browser-service'
+
+const services = [
+  new BrowserService(),
+]
+
+export default services

tslint.json

@@ -4,12 +4,16 @@
     "semicolon": [true, "never"],
     "indent": [true, "spaces", 2],
     "quotemark": [true, "single"],
-    "eofline": false
+    "eofline": false,
+    "arrow-parens": false,
+    "ordered-imports": false
   },
   "jsRules": {
     "semicolon": [true, "never"],
     "indent": [true, "spaces", 2],
     "quotemark": [true, "single"],
-    "eofline": false
+    "eofline": false,
+    "arrow-parens": false,
+    "ordered-imports": false
   }
 }