Elm version of Mark Seemann's KataTennis.
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This repo contains an implementation of Mark Seemann's KataTennis in Elm.

Mark wrote an article series called Types + Properties = Software.

The stronger a language's type system is, the more you can use static types to model your application's problem domain. With a sufficiently strong type system, you can make illegal states unrepresentable. While states are guaranteed to be legal, transitions between states need not be. You can often use Property-Based Testing to ensure that the state transitions are correct. The combination of types and properties give you a simple, but surprisingly powerful way of specifying the behaviour of the software you create.

Each article from the series has its own commit:

Running tests

To run tests, install node-test-runner, go to the root of the repo and call elm test from the terminal.