clarify Dockerfile templating in integration test docs
@@ -14,7 +14,12 @@ To run these tests through a cloudbuild, add the following build step to the **e
**It's crucial that this step appears after your image under test has been built**; without a built image, there will be nothing to test, and your build will fail!
-The sample application directory should contain the application fulfilling the integration test spec, as well as the build artifacts necessary to deploy the application via gcloud (namely, a templated Dockerfile and an app.yaml).
+The sample application directory should contain the application fulfilling the integration test spec, as well as the necessary build artifacts to deploy the application via gcloud, which means at minimum:
+
+ * a templated Dockerfile, with the first line being
+ ` FROM ${STAGING_IMAGE} `
+
+ * an app.yaml config
Alternatively, the application can be manually deployed *before* running the tests; in this scenario, the '--no-deploy' flag can be passed to the build step to opt out of deploying, in tandem with the URL at which the deployed application can be accessed:
