Test runner. Mocha.js

Test runner - фреймворк, основная функция которого - это инициализация тестовой среды и запуск тестов.

Самым популярным среди таких фреймворков является Mocha

Пример простой конфигурации тестового файла

describe('Test module name', () => {
    before(() => {
        // block in which some functionality would be executed
        // prior all tests in current describe block
    });
    
    beforeEach(() => {
        // block in which some functionality would be executed
        // prior each test in current describe block
    });
    
    afterEach(() => {
        // block in which some functionality would be executed
        // after each test in current describe block
    });
    
    after(() => {
        // block in which some functionality would be executed
        // after all tests in current describe block
    });
    
    it('Some test here', () => {
        console.log('first test');
    });
});