Quality Assurance

What needs to be tested?

How extensively do I test?

Are 10 unit tests better than 1 integration test?

Should I write tests even if I'm the only developer?

Do I need E2E tests?

Shouldn't the QA engineer write tests for me?

It depends

Codebase size

Team size

(git blame is not enough)

(complexity grows exp.)

Technology

(types? encapsulation? lint?)

Code quality

(refactoring)

$$$

(server is down = millions of $ go to the toilet)

Effective testing

Write test code as you write application code (TDD)

80/20 rule: which 20% of tests will cover 80% of the cases?

Think about testing when you write application code (separation of concerns, DI, service layer, pure functions)

Use tooling - test coverage

Think what code is most crucial

Top to bottom

Test code that...

Is being run the most

Is being used the most

Is complex (math, data processing, async)

Can have edge cases (usually unit tests)

Has a crucial business value (Auth, Payments...)

Unit test

1 unit = function / class

all else is mocked

Integration test

Endpoint test => routing + view/serialization

Component test?

Less mocking

Acceptance test

Series of endpoint tests

visit a URL => interact => check the result

POST /api/register => POST /api/login => GET /api/kingdom

/login => fill the login form => check that I'm on /kingdom

E2E test

Usually via external tool (Selenium, Cypress.io, Puppeteer)

Testing against real backend

qa.app.com

Integration tests

Acceptance tests

E2E tests

Unit tests

Test coverage

Visual testing

Nice, but rarely done:)

QA Q&A

assert(endOfPresentation, true);
assert.greaterThan(satisfactionPct, 90);

Thank you

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