Add unittest for rec_subs

Signed-off-by: Songmin Li <lisongmin@protonmail.com>

tests/unit/test_rec_subs.py

@@ -0,0 +1,62 @@
+# SPDX-License-Identifier: GPL-2.0
+# pylint: disable=protected-access
+
+import unittest
+
+from parameterized import parameterized
+
+from podman_compose import rec_subs
+
+
+class TestRecSubs(unittest.TestCase):
+    substitutions = [
+        # dict with environment variables
+        (
+            "service's environment is low priority",
+            {"environment": {"v1": "low priority", "actual-v1": "$v1"}},
+            {"environment": {"v1": "low priority", "actual-v1": "high priority"}},
+        ),
+        (
+            "service's environment can be used in other values",
+            {"environment": {"v100": "v1.0.0", "image": "abc:$v100"}},
+            {"environment": {"v100": "v1.0.0", "image": "abc:v1.0.0"}},
+        ),
+        (
+            "Non-variable should not be substituted",
+            {"environment": {"non_var": "$$v1", "vx": "$non_var"}, "image": "abc:$non_var"},
+            {"environment": {"non_var": "$v1", "vx": "$v1"}, "image": "abc:$v1"},
+        ),
+        # list
+        (
+            "Values in list are substituted",
+            ["$v1", "low priority"],
+            ["high priority", "low priority"],
+        ),
+        # str
+        (
+            "Value with ${VARIABLE} format",
+            "${v1}",
+            "high priority",
+        ),
+        (
+            "Value with ${VARIABLE:-default} format",
+            ["${v1:-default}", "${empty:-default}", "${not_exits:-default}"],
+            ["high priority", "default", "default"],
+        ),
+        (
+            "Value with ${VARIABLE-default} format",
+            ["${v1-default}", "${empty-default}", "${not_exits-default}"],
+            ["high priority", "", "default"],
+        ),
+        (
+            "Value $$ means $",
+            "$$v1",
+            "$v1",
+        ),
+    ]
+
+    @parameterized.expand(substitutions)
+    def test_rec_subs(self, desc, input, expected):
+        sub_dict = {"v1": "high priority", "empty": ""}
+        result = rec_subs(input, sub_dict)
+        self.assertEqual(result, expected, msg=desc)