Football leaderboard kata

This kata is about applying TDD in the presence of untestable dependencies. In the way that it's done in Kent Beck's original style of TDD, it seems to be in contrast with the London school but the two styles can actually be used in combination. Your task is to write a rest-api that uses another lower level rest-api. Do not mock this external API until you experience some difficulty with them (too slow, or flaky, ...). You definately want to explore the other api's behaviour with unit tests. Then once you have a few tests, you can refactor the tests to something more in line with the testing pyramid.

Start with a guiding system-level test. You'r priority is to get the integration points right, i.e. calling the external api correctly and providing the right value on your http endpoint. Once you have that you can probably get the interal logic right with traditional fast unit tests.

At the end I expect you'll have three types of tests, system-tests, focused integration-tests and unit-tests. Personally I separate those tests in my CI so that I can run them without polluting the unit tests with "random" failures but still get the valuable information that an external api is down/broken.

The external api

This is code out of your control.
It is provided as a lib and a docker container that you can start.

as a lib

cd typescript
npm install
npm run start-events-api

or you can install it globally

npm install -g football-events-api
start-footballs-events-api

using docker docker

docker run --name footballs-events-api -p 5010:5010 footballs-events-api

You now have a webserver running you can get todays events on http://localhost:5010/events

This api responds with a list of all game events, like goals etc.

Task

Write a rest-api that serve data for a score-board with todays' football games.

You don't have to worry about formatting, just return JSON of the form

[
  { "home": "Barcelona", 
    "visitor": "Madrid", 
    "score": [0, 1], 
    "state": "in progress" }
]

Questions for the retrospective

• What did the tests on with the real dependency teach you?
• What types of tests did you end up with? System-tests, unit tests, focused integration tests? All three?
• What problems were avoided, what was encountered?
• Could this be useful in your work? Can you share your thoughts?
• If this is the way you already work. What experiences can you share?
• What do you do with focused integration tests in the CI?

TODOs

• publish docker
• make sure there is some coordination between external ws so that they can't be that easily mocked out