Add tests.

.gitignore

@@ -0,0 +1 @@
+/__pycache__

circle.yml

@@ -5,8 +5,10 @@ machine:
 
 dependencies:
   pre:
-    - pip install pylint
+    - pip install nose pylint
 
 test:
   override:
     - pylint -d invalid-name docker-rerun
+    - nosetests test.py
+

test.py

@@ -0,0 +1,42 @@
+#!/usr/bin/python3
+
+import subprocess
+import unittest
+
+
+class RerunTest(unittest.TestCase):
+
+
+    def _run(self, cmd):
+        subprocess.call(cmd,
+                        stdout=subprocess.DEVNULL,
+                        stderr=subprocess.DEVNULL)
+
+
+    def test_command_matches(self):
+        """
+        Tests that the command used to start a docker container exactly matches
+        that returned by ./docker-rerun --dry-run.
+        """
+        commands = [
+            'docker run --name=test123 -d hello-world',
+            'docker run --name=test123 --restart=always -d hello-world',
+            'docker run --name=test123 --restart=on-failure:10 -d hello-world',
+            'docker run --name=test123 --net=host -d hello-world',
+            'docker run --name=test123 -d -p=127.0.0.1:443:443/tcp -p=127.0.0.1::1336/tcp hello-world',
+            'docker run --name=test123 -d -p=443/tcp hello-world',
+            'docker run --name=test123 --volume=/dev/null:/null --volume=/dev/urandom:/mnt/random -d hello-world',
+        ]
+
+        for command in commands:
+            with self.subTest(cmd=command):
+                self._run(['docker', 'rm', '-f', 'test123'])
+                self._run(command.split(' '))
+                output = subprocess.check_output(['./docker-rerun', '--dry-run', 'test123'])
+                output = output.decode('utf-8').strip().splitlines()
+                self.assertEqual(output[3], command)
+                self._run(['docker', 'rm', '-f', 'test123'])
+
+
+if __name__ == '__main__':
+    unittest.main()