Testcontainers Podman Demo

The goal of this project is twofolded:

• First, I want to write my first tests ever with Testcontainers and start to learn more about it
• Second, I want to learn about Podman and other container technologies besides Docker to boost my daily coding life

Local Database Setup

In order to test something with Testcontainers, we will need an actual application setup first.

I will use a Postgre database instance running via Podman, which exposes the connection on localhost:5432:

podman run \
-p 5432:5432 \
-e POSTGRES_PASSWORD='<PASSWORD>' \
--name postgres postgres

And for any consecutive runs, just restart the container:

podman restart postgres

In order to connect Spring boot with the database, you need to set the following two properties as environment variables:

SPRING_DATASOURCE_USERNAME=<USERNAME>
SPRING_DATASOURCE_PASSWORD=<PASSWORD>

The default username of postgres is postgres and the password is the one you set in the podman run command above. Further, postgres's default database name is also postgres, which is preset in the application.properties file.

Getting Testcontainers to run

First, we will need a podman VM that will run our containers later

podman machine init

Now, we can start the VM:

podman machine start

And check its connectivity via, which could like follows:

podman system connection list

% podman system connection list
Name                         Identity                                           URI
podman-machine-default*      /Users/<USER>/.ssh/podman-machine-default  ssh://core@localhost:53136/run/user/1000/podman/podman.sock
podman-machine-default-root  /Users/<USER>/.ssh/podman-machine-default  ssh://root@localhost:53136/run/podman/podman.sock

This will give us the port and the path to the podman.sock file.

Now, we can expose the podman.sock to the outside world (the host machine) and thus make it available to Testcontainers:

ssh -i \
~/.ssh/podman-machine-default \
-N core@localhost \
-p 53136 \
-L'/tmp/podman.sock:/run/user/1000/podman/podman.sock'

The ssh options are as follows:

- i: allows us to specify an identity file to use for the connection
- p: specify the port to establish the SSL connection on. Note: The VM does not expose SSH on 22 as usually done
- N: do not execute anything. Keeps the terminal window open
- L: Forward connections from the local socket to the remote socket

Especially -L is important in order to get access into the VM based on a file, which can then be referenced as follows (or whatever is your OS's approach to export environment variables) on the host machine where we want to run Testcontainers:

export DOCKER_HOST=unix:///temp/podman.sock

You will also need to set other environment variables to circumvent errors:

As described in the GitHub issue about connection to Ryuk, you will need to disable it (with all consequences):

export TESTCONTAINERS_RYUK_DISABLED=true

Now, it is on you where to set these parameters: Either directly in the IDE or on the system/user level of the OS. The latter is requried to run mvn commands on the project.

Running actual Testcontainer tests

Setting up a postgres environment for the test cases can be made super easy by following the testcontainer jdbc syntax. This allows to slightly adjust the current jdbc url from our application code and make testcontainers spawn the postgres database automatically:

Instead of this URL in the application.properties under src/main/resources:

spring.datasource.url=jdbc:postgresql://localhost:5432/postgres

We do this in the application properties under src/test/resources:

spring.datasource.url=jdbc:tc:postgresql:14.2:///integration-tests-db

The important part is the tc in between jdbc and postgresql. This will set the version of the postgres container to 14.2 and create a database called intergration-tests-db.

In the actual tests, there is no further setup required, this will do as a stupid-simple test:

@SpringBootTest
class CharacterRepositoryTest {

    @Autowired
    private CharacterRepository repository;

    @Test
    void empty_database_on_init() {
        List<Character> characters = (List<Character>) repository.findAll();

        assertTrue(characters.isEmpty());
    }
}

If you want to set the environment variables via your IDE (e.g. IntelliJ), you can do that for all your JUnit test cases by going to Run > Edit configurations > select JUnit > Edit configuration template and then set all variables there. Whenever you create a new JUnit configuration now, the variables are taken from the template.

Troubleshooting

Address already in use

When you try to setup the SSH tunnel to the VM, you get the the following error:

ssh -i ~/.ssh/podman-machine-default core@localhost -p 53136 -L'/tmp/podman.sock:/run/user/1000/podman/podman.sock'

unix_listener: cannot bind to path /tmp/podman.sock: Address already in use
Could not request local forwarding.
Fedora CoreOS 35.20220213.2.0
Tracker: https://github.com/coreos/fedora-coreos-tracker
Discuss: https://discussion.fedoraproject.org/tag/coreos

Last login: Fri Feb 25 14:51:28 2022 from 192.168.127.1
[core@localhost ~]$

Although you are ssh'd into the VM afterwards, the tunnel setup failed.

You can jump out of the VM and then delete the local .sock:

1. Jump out of the VM:

[core@localhost ~]$ exit

2. Delete the .sock file locally:

rm /tmp/podman.sock