Because Web API Testing Should Be Easy Honza Javorek

Because Web API Testing Should Be Easy Honza Javorek

Design APIs for humans and test what you promised Honza Javorek

Honza honzajavorek.cz

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Interface of libraries pip install django

Interface of systems curl https://api.github.com/repos/django/django curl http://www.cnb.cz/cs/financni_trhy/devizovy_trh/ kurzy_devizoveho_trhu/denni_kurz.txt

User interface

import urllib2 gh_url = 'https://api.github.com' req = urllib2.Request(gh_url) password_manager = urllib2.HTTPPasswordMgrWithDefaultRealm() password_manager.add_password(None, gh_url, 'user', 'pass') auth_manager = urllib2.HTTPBasicAuthHandler(password_manager) opener = urllib2.build_opener(auth_manager) urllib2.install_opener(opener) handler = urllib2.urlopen(req) print handler.getcode() print handler.headers.getheader('content-type') Do you like this interface?

Requests: HTTP for Humans

>>> r = requests.get('https://api.github.com/user', ... auth=('user', 'pass')) >>> r.status_code 200 >>> r.headers['content-type'] 'application/json; charset=utf8' >>> r.encoding 'utf-8' >>> r.text '{"type":"User"...' >>> r.json() {'disk_usage': 368627, 'private_gists': 484, ...} Do you like this interface?

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How did Kenneth do it?

How do you design the interface?

def test_basic_building(): req = requests.Request() req.url = 'http://kennethreitz.org/' req.data = {'life': '42'} pr = req.prepare() assert pr.url == req.url assert pr.body == 'life=42'

Writing tests first helps to design the interface TDD

test > RED > implement > test > GREEN req = requests.Request() req.url = 'http://kennethreitz.org/' req.data = {'life': '42'} pr = req.prepare() assert pr.url == req.url assert pr.body == 'life=42'

Writing down behavior first helps to design the interface BDD

Feature: Status code Background: Given you expect HTTP status code "200" Scenario: Different real response status When real status code is "500" Then Gavel will set some error for "status code" And Request or Response is NOT valid Scenario: Response status code match When real status code is "200" Then Gavel will NOT set any errors for "status code" And Request or Response is valid Gherkin / Cucumber

Testable documentation!

RDD

RDD Readme Driven Development http://tom.preston-werner.com/2010/08/23/readme-driven- development.html

# Requests The `requests` library allows you to perform HTTP requests from your Python code. ## Example ```python >>> r = requests.get('https://github.com') >>> r.status_code 200 ``` ## License MIT README.md

Readme Driven Development • chance to think through the project first • docs are ready - no need to write them retroactively • your team can use the interface before it exists • easy to discuss the interface with everyone

Interface in README = Essential interface user expects

README must not get out of sync with code

How do we ensure implementation matches the design?

python -m doctest README.md doctest

language: "python" python: - "3.6" script: - "python -m doctest README.md" Continuous Integration

What if we could design and test web APIs like this?

# Calendar API The API gives you various means to work with date and time. ## GET /now Provides you with current date and time. - Response 200 (application/json) ```json { "day": 29, "month": 2, "year": 2017, "hour": 11, "minute": 45, "second": 38 } ``` API.md

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dredd API.md http://localhost:8000 Dredd

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language: "python" python: - "3.6" before_install: - "npm install -g dredd" script: - "dredd API.md http://localhost:8000" Continuous Integration

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Testing implementation against design allows you designing before implementing

Designing before implementing allows you better design

Dredd allows you better design

Demo

Remember • think first, design first, docs first, test first • discuss the the interface design before implementing • use the interface before implementing (mocks, tests) • have your interface design as a single source of truth • test implementation against the design

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