se the standard library&#39;s <code>StringIO</code> to both capture the output and supress it from your test&#39;s standard output/error.</p><p><code>executor</code> is a <a href="/api/Brut/CLI/Executor.html" target="_self" rel="noopener" data-no-router><code>Brut::CLI::Executor</code></a>, which is a wrapper around the standard library&#39;s <code>Open3</code>. You can mock this to set expectations on what child processes are launched and how they behave.</p><h2 id="recommended-practices" tabindex="-1">Rec