chore: combine tests and ensure that pack is selected

tests/unit/builder-pack.bats

@@ -103,3 +103,26 @@ teardown() {
   echo "status: $status"
   assert_success
 }
+
+@test "(ps) cnb env vars" {
+  run /bin/bash -c "dokku config:set $TEST_APP APP_RESPECTS_ENV_VARS=1"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku builder:set $TEST_APP selected pack"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run deploy_app python dokku@$DOKKU_DOMAIN:$TEST_APP add_requirements_txt_cnb
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "curl $(dokku url $TEST_APP)/env"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output_contains '"APP_RESPECTS_ENV_VARS": "1"'
+}