Blog Post: Some Elixir Testing Tricks

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This is my current command to run the tests:

mix test --failed --max-failures 1 --seed $(odo -c _build/seed.txt) && \
mix test --stale  --max-failures 1 --seed $(odo -c _build/seed.txt) && \
odo _build/seed.txt

odo is a simple counter that reads or increments a number from a file.

So what is does is:

  • as long as I have a failing test, it will only run that test, thanks to the seed
  • when this test passes, it will now fail repeatedly on the next failing test
  • when all my previously failing tests pass, it will run all the stale tests. If one of them fails, the loop will start over.
  • if everything passes, we increment the seed to preserve a minimum of entropy like designed in ExUnit.

A simple shortcut for vscode:

  {
    "key": "ctrl+alt+u",
    "command": "workbench.action.terminal.sendSequence",
    "args": {
      "text": "mix test --failed --max-failures 1 --seed $(odo -c _build/seed.txt) && mix test --stale --max-failures 1 --seed $(odo -c _build/seed.txt) && odo _build/seed.txt\n"
    }
  },
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