Testing container is one of the major reason for the existence of the tool gotun. In this blog post, I am going to show you how easy it becomes to test a container. But, easy is still a relative term. If setting up your container requires very complex steps, then you will have to do those first. And then, finally, you can test the application. You can use Ansible to do the hard part of setting up the application.

Fedora Redis container

In our example, we will test the Fedora Redis container. Redis is an in-memory data structure store. We use it as key: value store, as a database. It can also hold some complex infrastructures.

Let me post the test commands first.

sudo docker run -d --name redis fedora/redis
sudo docker run  -d --link redis:rd --name client fedora/redis
COPY: ./redistests.py vm1:./
sudo python3 -m unittest redistests.RedisTest.test_set -v
sudo python3 -m unittest redistests.RedisTest.test_append -v
sudo docker rm -f client
sudo python3 -m unittest redistests.RedisTest.test_newclient -v

In the first line, I am starting a new redis container. In the second line, I am running a container named “client”. In the next two lines, I have two tests. I will be using this container in those two tests. Then I will delete the container, and as the part of the last test, we will create a new container, and connect to the redis server container to get the value for the key name.

In the third line, I am copying a Python3 unittest file over to the VM, and then executing the tests one by one. I wanted to check the output from the redis-cli command instead of the exit code, that is why I decided to use Python unittest module. It makes parsing the output text much easier, and we can do complex analysis of the output text. We follow the same style in the Fedora Atomic tests.

redistests.py

import unittest
import subprocess

def system(cmd):
    """
    Invoke a shell command.
    :returns: A tuple of output, err message, and return code
    """
    ret = subprocess.Popen(cmd, shell=True, stdin=subprocess.PIPE,
                stdout=subprocess.PIPE, stderr=subprocess.PIPE, close_fds=True)
    out, err = ret.communicate()
    return out.decode("utf-8"), err.decode("utf-8"), ret.returncode


class RedisTest(unittest.TestCase):

    def test_set(self):
        out, err, eid = system("docker exec client redis-cli -h rd SET name kushal")
        out, err, eid = system("docker exec client redis-cli -h rd GET name")
        self.assertEqual(out, "kushal\n")

    def test_append(self):
        system("docker exec client redis-cli -h rd DEL clients")
        out, err, eid = system("docker exec client redis-cli -h rd APPEND clients ABC")
        self.assertEqual(out, "3\n")
        out, err, eid = system("docker exec client redis-cli -h rd APPEND clients XYZ")
        self.assertEqual(out, "6\n")
        out, ere, eid = system("docker exec client redis-cli -h rd GET clients")
        self.assertEqual(out, "ABCXYZ\n")

    def test_newclient(self):
        out, err, eid = system("docker run --rm --link redis:r2d2 --name newclient fedora/redis redis-cli -h r2d2 GET name")
        self.assertEqual(out, "kushal\n")

The output from the job.

$ ./gotun --job commands
Starts a new Tunir Job.

Server ID: cb0f491d-a921-46dd-b6e1-3c4353884d6c
Let us wait for the server to be in running state.
Time to assign a floating pointip.
Polling for a successful ssh connection.

Polling for a successful ssh connection.

Polling for a successful ssh connection.

Polling for a successful ssh connection.

Polling for a successful ssh connection.

Executing:  sudo docker run -d --name redis fedora/redis
Executing:  sudo docker run  -d --link redis:rd --name client fedora/redis
Executing COPY:  scp -o StrictHostKeyChecking=no -r -i /home/kdas/Downloads/kushal-testday.pem ./redistests.py fedora@209.132.184.210:./
Executing:  sudo python3 -m unittest redistests.RedisTest.test_set -v
Executing:  sudo python3 -m unittest redistests.RedisTest.test_append -v
Executing:  sudo docker rm -f client
Executing:  sudo python3 -m unittest redistests.RedisTest.test_newclient -v
---------------


Result file at: /tmp/tunirresult_210751937


Job status: true


command: sudo docker run -d --name redis fedora/redis
status:true

Unable to find image 'fedora/redis:latest' locally
Trying to pull repository docker.io/fedora/redis ... 
sha256:1bb7b6c03575dd43db6e8e3fc0b06c0b3df0178af9ea382b6f9df577d053bd22: Pulling from docker.io/fedora/redis
a3ed95caeb02: Pull complete 
cadab8e68e03: Pull complete 
9db1d534feda: Pull complete 
a4d5e4eefba6: Pull complete 
Digest: sha256:1bb7b6c03575dd43db6e8e3fc0b06c0b3df0178af9ea382b6f9df577d053bd22
Status: Downloaded newer image for docker.io/fedora/redis:latest
b83c3f13fa698627447575651e585f3308e795f579ea772c66d02ae0f1c72939


command: sudo docker run  -d --link redis:rd --name client fedora/redis
status:true

6096e414e2f7c314c9601ae6eaedbb3faf9fb265b70a4f77e5ba7b9a93b19209


command: sudo python3 -m unittest redistests.RedisTest.test_set -v
status:true

test_set (redistests.RedisTest) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.199s

OK


command: sudo python3 -m unittest redistests.RedisTest.test_append -v
status:true

test_append (redistests.RedisTest) ... ok

----------------------------------------------------------------------
Ran 1 test in 0.289s

OK


command: sudo docker rm -f client
status:true

client


command: sudo python3 -m unittest redistests.RedisTest.test_newclient -v
status:true

test_newclient (redistests.RedisTest) ... ok

----------------------------------------------------------------------
Ran 1 test in 1.298s

OK


Total Number of Tests:6
Total NonGating Tests:0
Total Failed Non Gating Tests:0

Success.