A rebar plugin that allows you to run code before rebar3 eunit does its thing.

It's useful for starting applications (such as telemetry) that your code depends on, without scattering fixtures all over your tests.

If you're looking for the equivalent for Common Test, that's here: https://github.com/rlipscombe/ct_ext/

Add the plugin to your rebar config:

{profiles, [
    {test, [
        {plugins, [
            {rebar3_eunit_start, {git, "https://github.com/rlipscombe/rebar3_eunit_start.git", {tag, "0.1.0"}}}
        ]},
        {provider_hooks, [{pre, [{eunit, {default, rebar3_eunit_start}}]}]}
    ]}
]}.

Configure the applications and/or modules to start:

{eunit_opts, [
    % ...
    {start_applications, [telemetry]},
    {start_modules, [test_helper]}
]}.

It starts the listed applications and then the listed modules. The applications are passed to application:ensure_all_started/1. For each module listed, the Module:start/0 function is called. The modules are started in the order given.

Then run rebar3 eunit as normal:

$ rebar3 eunit

Before eunit runs your tests, the telemetry application will be started, and test_helper:start() will be called.

Add the plugin to your rebar config as above, and then add symlink from the plugins directory:

cd _build/default/plugins/
ln -sf path/to/rebar3_eunit_start .

When you make changes to the plugin, delete the ebin directory in this directory, so that rebar recompiles it.