Setup default image when cleaning up containers

postgres-appliance/tests/README.md

@@ -0,0 +1,21 @@
+# Run tests
+
+After building the image, you can test your image by:
+
+1. Setting up the environment variable `SPILO_TEST_IMAGE` to test the specific image. If unset, the default will be `spilo`.
+    ```
+    export SPILO_TEST_IMAGE=<your_spilo_image>
+    ```
+2. Run the test:
+    ```
+    bash test_spilo.sh
+    ```
+    To enable debugging for an entire script when it runs:
+    ```
+    bash -x test_spilo.sh
+    ```
+
+The test will create multiple containers. They will be cleaned up by the last line before running `main` in `test_spilo.sh`. To keep and debug the containers after running the test, this part can be commented.
+```
+trap cleanup QUIT TERM EXIT
+```

postgres-appliance/tests/test_spilo.sh

@@ -12,7 +12,7 @@ readonly TIMEOUT=120
 
 function cleanup() {
     stop_containers
-    docker ps -q --filter="ancestor=${SPILO_TEST_IMAGE}" --filter="name=${PREFIX}" | xargs docker rm -f
+    docker ps -q --filter="ancestor=${SPILO_TEST_IMAGE:-spilo}" --filter="name=${PREFIX}" | xargs docker rm -f
 }
 
 function get_non_leader() {