testing.md

Testing

The software system comes with an opinionated framework for testing of both backend and frontend. For frontend, DOM testing is utilized.

Guide

Backend

In the backend, the recommendation is to test all command handlers and non-trivial query handlers. This should also cover testing of domain services. A test might look something like this:

import { Repository } from "typeorm";

import { createMockRepository } from "src/test/mocks/repository.mock";

import { MonkeyService } from "../../domain/services/monkey.service";
import { Monkey } from "../../infrastructure/entities/monkey.entity";
import { CreateMonkeyHandler } from "./create-monkey.handler";

describe(CreateMonkeyHandler.name, () => {
  let monkeyService: MonkeyService;
  let commandHandler: CreateMonkeyHandler;
  let monkies: Repository<Monkey>;

  beforeEach(() => {
    monkies = createMockRepository<Monkey>();
    monkeyService = new MonkeyService(monkies);
    commandHandler = new CreateMonkeyHandler(monkeyService);
  });

  describe("can create monkey", () => {
    it("should save changes", async () => {
      await commandHandler.execute();

      expect(monkies.save).toHaveBeenCalled();
    });
  });
});

Frontend

In the frontend, components should have tests where needed due to DOM-testing being resource-heavy. A test can be written as below:

import { render, screen } from "src/test";

import { Button } from ".";

describe("<Button />", () => {
  it("renders", () => {
    render(<Button>my-text</Button>);
    const text = screen.getByText(/my-text/);
    expect(text).toBeInTheDocument();
  });
});

Coverage

Coverage is calculated for test runs and each service has a required minimum coverage threshold. These thresholds should not be set in stone, but adjusted after need. They should serve as a guard for not forgetting to write tests.