TDD in Erlang - part 1: Project Skeleton
I have wanted to learn Erlang for a long time and I bought Joe Armestrongs book 'Programming Erlang' over two years ago. But it was not until recently I sat down and actually read it and tried out the examples. I was intrigued, someone had really put their mind into creating a language for high availability concurrent applications. To deepen my understanding of Erlang I have a medium sized project in mind and I have decided that I want to develop it fully test driven. The test framework that I have decided to use is EUnit. It seams to be the most commonly used unit test framework within the Erlang community. To start this up my first order of business was to create a project structure where I separate acceptance test, unit tests and production code from each other. With a build script that builds everything and runs all tests.
The project structure
The project directory structure illustrated by an ascii drawing.
[root] | -- src | | | -- main | -- test | | | -- acceptance | -- unit | -- build.sh
Build script
The build script creates a temporary folder under the project root called build and into this folder it outputs the compiled modules. Part of build script that compiles the unit test and the main source code.
# compile main source erlc -o build/out/main src/main/*.erl # compile unit tests erlc -o build/out/unit test/unit/*.erl
Part of the build script that executes the unit tests.
erl -noshell\ -pa build/out/main build/out/unit\ -run unit_test_suite run build/out/unit\ -s init stop
erl -noshell This starts Erlang without an interactive shell -pa build/out/main build/out/unit This adds the two paths to the compiled modules, \'build/out/main\' and \'build/out/unit\', to the code path so that they are found by Erlang which where started in the project root. -run unit_test_suite run build/out/unit This evaluates the function run in module unit_test_suite with the path to the compiled unit tests modules as an argument \'build/out/unit\'). -s init stop After the evaluation of the function unit_test_suite:run has finished the function init:stop is evaluated which tears down Erlang nicely. The full project can be found at github here. Note that this project will grow and change. To get it in the state it was when this blog post was written (which was this):
git init git clone https://github.com/Discordia/Erlang-Project-Skeleton git checkout 7ed1ed28bd1916d31637e500c026310840b8b83e