Testing With Julia

The standard way of writing tests Julia is to write a test/runtests.jl file. Running Pkg.test() will when start a new Julia process that loads your package and runs this file.

Starting a new process to run your test might make sense for languages like Python, where spinning up a new process is easy. But in Julia, making a new process and loading your package from scratch can take a very long time. Doing this every time you want to test your code (which, if you’re doing some form of test driven development, might be every thirty seconds) is a recipe for exasperation.

Fortunately, there’s a way around Julia’s long startup times: the Revise module. Don’t use the built in Pkg.test() function. Just include the test file after activating the test environment and importing Revise. You’ll need to do a little setup the first time you try this out, as the environment won’t be instantiated. Run

] activate test
dev .
instantiate

From here on out, you can test with

] activate test
using Revise
include("test/runtests.jl")

You can even wrap the whole thing in the entr function, which will re-run the tests whenever you make a change.

Revise.entr(["test"]; all=true) do
    include("test/runtests.jl")
end

Together with stuff like TidyTest, this makes the testing experience in Julia almost as nice as pytest-watch for Python.