feat: split out test files and execute them manually

This breaks the old grouping mechanism, but honestly that was a weird way of doing it.

tests/unit/storage.bats

@@ -0,0 +1,56 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  global_setup
+  create_app
+}
+
+teardown() {
+  destroy_app
+  global_teardown
+}
+
+@test "(storage) storage:help" {
+  run /bin/bash -c "dokku storage"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output_contains "Manage mounted volumes"
+  help_output="$output"
+
+  run /bin/bash -c "dokku storage:help"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output_contains "Manage mounted volumes"
+  assert_output "$help_output"
+}
+
+@test "(storage) storage:mount, storage:list, storage:umount" {
+  run /bin/bash -c "dokku storage:mount $TEST_APP /tmp/mount:/mount"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  run /bin/bash -c "dokku storage:list $TEST_APP | grep -qe '^\s*/tmp/mount:/mount'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  run /bin/bash -c "dokku storage:mount $TEST_APP /tmp/mount:/mount"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output "Mount path already exists."
+  assert_failure
+  run /bin/bash -c "dokku storage:unmount $TEST_APP /tmp/mount:/mount"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  run /bin/bash -c "dokku storage:list $TEST_APP | grep -vqe '^\s*/tmp/mount:/mount'"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  run /bin/bash -c "dokku storage:unmount $TEST_APP /tmp/mount:/mount"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output "Mount path does not exist."
+  assert_failure
+}