Adds Pest tests. Starts GH Action.

tests/Support/Output.php

@@ -0,0 +1,17 @@
+<?php
+
+namespace Tests\Support;
+
+use Illuminate\Support\Collection;
+
+class Output
+{
+    public static function containerList($rawOutput): Collection
+    {
+        $outputLines = explode(PHP_EOL, $rawOutput);
+
+        return collect($outputLines)
+            ->reject(fn($line) => empty($line))
+            ->map(fn($outputLine) => json_decode($outputLine, flags: JSON_THROW_ON_ERROR));
+    }
+}