tests/integration: Automate manual 'interpolation' test

Signed-off-by: Monika Kairaityte <monika@kibit.lt>

tests/integration/interpolation/docker-compose.yml

@@ -4,8 +4,8 @@ services:
         image: busybox
         command: ["/bin/busybox", "sh", "-c", "export | grep EXAMPLE"]
         environment:
-            EXAMPLE_VARIABLE: "Host user: $USER"
-            EXAMPLE_BRACES: "Host user: ${USER}"
+            EXAMPLE_VARIABLE: "Host user: $EXAMPLE_VARIABLE_USER"
+            EXAMPLE_BRACES: "Host user: ${EXAMPLE_VARIABLE_USER}"
             EXAMPLE_COLON_DASH_DEFAULT: ${NOT_A_VARIABLE:-My default}
             EXAMPLE_DASH_DEFAULT: ${NOT_A_VARIABLE-My other default}
             EXAMPLE_DOT_ENV: $DOT_ENV_VARIABLE

tests/integration/test_podman_compose_interpolation.py

@@ -0,0 +1,45 @@
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import unittest
+
+from tests.integration.test_podman_compose import podman_compose_path
+from tests.integration.test_podman_compose import test_path
+from tests.integration.test_utils import RunSubprocessMixin
+
+
+def compose_yaml_path():
+    return os.path.join(os.path.join(test_path(), "interpolation"), "docker-compose.yml")
+
+
+class TestComposeInterpolation(unittest.TestCase, RunSubprocessMixin):
+    def test_interpolation(self):
+        try:
+            self.run_subprocess_assert_returncode([
+                "env",
+                "EXAMPLE_VARIABLE_USER=test_user",
+                podman_compose_path(),
+                "-f",
+                compose_yaml_path(),
+                "up",
+            ])
+            output, _ = self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                compose_yaml_path(),
+                "logs",
+            ])
+            self.assertIn("EXAMPLE_VARIABLE='Host user: test_user'", str(output))
+            self.assertIn("EXAMPLE_BRACES='Host user: test_user'", str(output))
+            self.assertIn("EXAMPLE_COLON_DASH_DEFAULT='My default'", str(output))
+            self.assertIn("EXAMPLE_DASH_DEFAULT='My other default'", str(output))
+            self.assertIn("EXAMPLE_DOT_ENV='This value is from the .env file'", str(output))
+            self.assertIn("EXAMPLE_EMPTY=''", str(output))
+            self.assertIn("EXAMPLE_LITERAL='This is a $literal'", str(output))
+        finally:
+            self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                compose_yaml_path(),
+                "down",
+            ])