Jest

Instalação

Instalação do Jest:

$ yarn add jest -D

Instalações das tipagens do Jest:

$ yarn add ts-jest @types/jest -D

Inicialização

Iniciar rodando o comando $ yarn jest --init e as respostas:

✔ Would you like to use Jest when running "test" script in "package.json"? … yes
✔ Choose the test environment that will be used for testing › node
✔ Do you want Jest to add coverage reports? … yes
✔ Automatically clear mock calls and instances between every test? … yes

Arquivo jest.config.js (Pode variar de acordo com cada projeto):

module.exports = {
  clearMocks: true,
  collectCoverageFrom: [
    "src/services/**/*.ts"
  ],
  coverageDirectory: "__tests__/coverage",
  coverageReporters: [
    "json",
    "lcov",
  ],
  testEnvironment: "node",
  testMatch: [
    "<rootDir>/__tests__/**/*.spec.ts",
  ],
  transform: {
    '^.+\\.ts$': 'ts-jest'
  },
};