diff --git a/README.md b/README.md
index 27856aef..0796da0c 100644
--- a/README.md
+++ b/README.md
@@ -34,6 +34,10 @@ Images are continuously pushed to the `:latest` tag.
 
 - Run the development server with `python -m pdf_service`
 - Run tests with `./test` or `./test-watch`
+  - Tests are executed within docker, to ensure render results are identical to the containerized
+    version. The image contains external dependencies, but code and test files will be mounted from
+    the project source. If you want to rebuild the dev image add `--build` to the end of the
+    command. This will instruct `docker-compose` to rebuild the image.
 
 ### Visual tests with reference images
 
diff --git a/test b/test
index e0cc0e67..a5c6d0c7 100755
--- a/test
+++ b/test
@@ -1,3 +1,3 @@
 #!/usr/bin/env sh
 
-docker-compose up --build test
+docker-compose up "$@" test
diff --git a/test-watch b/test-watch
index 18db2ca6..95574c36 100755
--- a/test-watch
+++ b/test-watch
@@ -1,3 +1,3 @@
 #!/usr/bin/env sh
 
-docker-compose up --build test-watch
+docker-compose up "$@" test-watch