Data simulation

Midway provides the built-in ability to simulate data during development and testing.

Mock during testing

@midwayjs/mock provides some more general APIs for simulation during testing.

Simulation context

mockContext methods are used to simulate the context.

import { mockContext } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {
  const app = await createApp();

  // Simulation context
  mockContext(app, 'user', 'midway');

  const result1 = await createHttpRequest(app).get('/');
  // ctx.user => midway
  // ...
});

If your data is complex or logical, you can also use the callback form.

import { mockContext } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {
  const app = await createApp();

  // Simulation context
  mockContext(app, (ctx) => {
    ctx.user = 'midway';
  });
});

Note that this mock behavior is executed before all middleware.

Analog Session

mockSession methods are used to simulate Session.

import { mockSession } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {
  const app = await createApp();

  mockSession(app, 'user', 'midway');

  const result1 = await createHttpRequest(app).get('/');
  // ctx.session.user => midway
  // ...
});

Simulate Header

Use mockHeader methods to simulate Header.

import { mockHeader } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {
  const app = await createApp();

  mockHeader(app, 'x-abc', 'bbb');

  const result1 = await createHttpRequest(app).get('/');
  // ctx.headers['x-abc'] => bbb
  // ...
});

Simulation class attribute

Use the mockClassProperty method to simulate the properties of the class.

If there is the following service class.

@Provide()
export class UserService {
  data;

  async getUser() {
    return 'hello';
  }
}

We can simulate it when we use it.

import { mockClassProperty } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {

  mockClassProperty(UserService, 'data', {
    bbb: 1
  });
  // userService.data => {bbb: 1}

  // ...
});

It is also possible to simulate the method.

import { mockClassProperty } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {

  mockClassProperty(UserService, 'getUser', async () => {
    return 'midway';
  });

  // userService.getUser() => 'midway'

  // ...
});

Simulate common object properties

Use the mockProperty method to mock object properties.

import { mockProperty } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {

  const a = {};
  mockProperty(a, 'name', 'hello');

  // a['name'] => 'hello'

  // ...
});

It is also possible to simulate the method.

import { mockProperty } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {

  const a = {};
  mockProperty(a, 'getUser', async () => {
    return 'midway';
  });

  // a.getUser() => 'midway'

  // ...
});

Clean up mock

Every time the close method is called, all mock data is automatically cleared.

If you want to clean up manually, you can also perform method restoreAllMocks.

import { restoreAllMocks } from '@midwayjs/mock';

it('should test create koa app with new mode with mock', async () => {
  restoreAllMocks();
  // ...
});

Standard Mock service

Midway provides standard MidwayMockService services for simulating data in code.

Various simulation methods in @midwayjs/mock have all called this service at the bottom.

For more information, see Built-in services.

Development Mock

Whenever the back-end service is not online, or when the data is not prepared during the development phase, the ability to simulate during the development phase is required.

Write mock class

Under normal circumstances, we will write the simulation data used during development in the src/mock folder, and our simulation behavior is actually a piece of logic code.

astuce

Don't get used to mocking data in code, it's actually part of the logic.

Let's take an example. If there is a service for obtaining Index data, but the service has not been developed yet, we can only write simulation code.

// src/service/indexData.service.ts
import { Singleton, makeHttpRequest, Singleton } from '@midwayjs/core';

@Singleton()
export class IndexDataService {
  
   @Config('index')
   indexConfig: {indexUrl: string};

   private indexData;

   async load() {
     // get data from remote
     this.indexData = await this.fetchIndex(this.indexConfig.indexUrl);
   }
  
   public getData() {
     if (!this. indexData) {
       // If the data does not exist, load it once
       this. load();
     }
     return this. indexData;
   }

   async fetchIndex(url) {
     return makeHttpRequest<Record<string, any>>(url, {
       method: 'GET',
       dataType: 'json',
     });
   }
}

astuce

In the above code, the fetchIndex method is intentionally removed to facilitate subsequent simulation behaviors.

When the interface has not been developed, it is very difficult for us to develop locally. The common practice is to define a JSON data,

For example, create a src/mock/indexData.mock.ts to mock the initial service interface.

// src/mock/indexData.mock.ts
import { Mock, ISimulation } from '@midwayjs/core';

@Mock()
export class IndexDataMock implements ISimulation {
}

@Mock is used to represent that it is a simulation class, which is used to simulate some business behaviors, and ISimulation is some interfaces that need to be implemented by the business.

For example, we want to simulate the data of the interface.

// src/mock/indexData.mock.ts
import { App, IMidwayApplication, Inject, Mock, ISimulation, MidwayMockService } from '@midwayjs/core';
import { IndexDataService } from '../service/indexData.service';

@Mock()
export class IndexDataMock implements ISimulation {

   @App()
   app: IMidwayApplication;

   @Inject()
   mockService: MidwayMockService;

   async setup(): Promise<void> {
     // Mock properties using the MidwayMockService API
     this.mockService.mockClassProperty(IndexDataService, 'fetchIndex', async (url) => {
       // return different data according to the logic
       if (/current/.test(url)) {
         return {
           data: require('./resource/current.json'),
         };
       } else if (/v7/.test(url)) {
         return {
           data: require('./resource/v7.json'),
         };
       } else if (/v6/.test(url)) {
         return {
           data: require('./resource/v6.json'),
         };
       }
     });
   }

   enableCondition(): boolean | Promise<boolean> {
     // Conditions for the mock class to be enabled
     return ['local', 'test', 'unittest']. includes(this. app. getEnv());
   }
}

In the above code, enableCondition is a method that must be implemented, which represents the enabling condition of the current simulation class. For example, the above code only takes effect in local, test and unittest environments.

Simulation Timing

The simulation class contains some simulation opportunities, which have been defined in the ISimulation interface, such as:

export interface ISimulation {
   /**
    * The initial simulation timing is executed after the life cycle onConfigLoad
    */
   setup?(): Promise<void>;
   /**
    * Executed when the life cycle is closed, generally used for data cleaning
    */
   tearDown?(): Promise<void>;
   /**
    * Executed when each framework is initialized, the app of the current framework will be passed
    */
   appSetup?(app: IMidwayApplication): Promise<void>;
   /**
    * Executed at the beginning of each frame's request, the app and ctx of the current frame will be passed
    */
   contextSetup?(ctx: IMidwayContext, app: IMidwayApplication): Promise<void>;
   /**
    * Executed at the end of each frame request, after error handling
    */
   contextTearDown?(ctx: IMidwayContext, app: IMidwayApplication): Promise<void>;
   /**
    * Executed when each frame is stopped
    */
   appTearDown?(app: IMidwayApplication): Promise<void>;
   /**
    * The execution conditions of the simulation are generally a specific environment or a specific framework
    */
   enableCondition(): boolean | Promise<boolean>;
}

Based on the above interface, we implement very free simulation logic.

For example, add different middleware on different frameworks.

import { App, IMidwayApplication, Mock, ISimulation } from '@midwayjs/core';

@Mock()
export class InitDataMock implements ISimulation {

   @App()
   app: IMidwayApplication;

   async appSetup(app: IMidwayApplication): Promise<void> {
     // Add different test middleware for different framework types
     if (app. getNamespace() === 'koa') {
       app. useMiddleware(/*...*/);
       app. useFilter(/*...*/);
     }
    
     if (app. getNamespace() === 'bull') {
       app. useMiddleware(/*...*/);
       app. useFilter(/*...*/);
     }
   }

   enableCondition(): boolean | Promise<boolean> {
     return ['local', 'test', 'unittest']. includes(this. app. getEnv());
   }
}