Chapter 5. Testing S2I Images

As an Source-to-Image (S2I) builder image author, you can test your S2I image locally and use the OpenShift Container Platform build system for automated testing and continuous integration.

As described in the S2I Requirements topic, S2I requires the assemble and run scripts to be present in order to successfully run the S2I build. Providing the save-artifacts script reuses the build artifacts, and providing the usage script ensures that usage information is printed to console when someone runs the container image outside of the S2I.

The goal of testing an S2I image is to make sure that all of these described commands work properly, even if the base container image has changed or the tooling used by the commands was updated.

The standard location for the test script is test/run. This script is invoked by the OpenShift Container Platform S2I image builder and it could be a simple Bash script or a static Go binary.

The test/run script performs the S2I build, so you must have the S2I binary available in your $PATH. If required, follow the installation instructions in the S2I README.

S2I combines the application source code and builder image, so in order to test it you need a sample application source to verify that the source successfully transforms into a runnable container image. The sample application should be simple, but it should exercise the crucial steps of assemble and run scripts.

The S2I tooling comes with powerful generation tools to speed up the process of creating a new S2I image. The s2i create command produces all the necessary S2I scripts and testing tools along with the Makefile:

s2i create _<image name>_ _<destination directory>_

$ s2i create _<image name>_ _<destination directory>_

The generated test/run script must be adjusted to be useful, but it provides a good starting point to begin developing.

The easiest way to run the S2I image tests locally is to use the generated Makefile.

If you did not use the s2i create command, you can copy the following Makefile template and replace the IMAGE_NAME parameter with your image name.

IMAGE_NAME = openshift/ruby-20-centos7
CONTAINER_ENGINE := $(shell command -v podman 2> /dev/null | echo docker)

build:
	${CONTAINER_ENGINE} build -t $(IMAGE_NAME) .

.PHONY: test
test:
	${CONTAINER_ENGINE} build -t $(IMAGE_NAME)-candidate .
	IMAGE_NAME=$(IMAGE_NAME)-candidate test/run

IMAGE_NAME = openshift/ruby-20-centos7
CONTAINER_ENGINE := $(shell command -v podman 2> /dev/null | echo docker)

build:
	${CONTAINER_ENGINE} build -t $(IMAGE_NAME) .

.PHONY: test
test:
	${CONTAINER_ENGINE} build -t $(IMAGE_NAME)-candidate .
	IMAGE_NAME=$(IMAGE_NAME)-candidate test/run

The test script assumes you have already built the image you want to test. If required, first build the S2I image. Run one of the following commands:

The following steps describe the default workflow to test S2I image builders:

Running these steps is generally enough to tell if the builder image is working as expected.

Once you have a Dockerfile and the other artifacts that make up your new S2I builder image, you can put them in a git repository and use OpenShift Container Platform to build and push the image. Simply define a Docker build that points to your repository.

If your OpenShift Container Platform instance is hosted on a public IP address, the build can be triggered each time you push into your S2I builder image GitHub repository. See webhook triggers for more information.

You can also use the ImageChangeTrigger to trigger a rebuild of your applications that are based on the S2I builder image you updated. See image change triggers for more information.