Add comprehensive tests for KVP splitting to prevent issue #35 regression

Co-authored-by: smurawski <4006985+smurawski@users.noreply.github.com>

Author: Copilot

src/tests/service/test_service_environment.py

@@ -1,6 +1,7 @@
 from unittest import TestCase
 
 from pycomposefile import compose_file
+from pycomposefile.compose_element.compose_list_or_map import ComposeListOrMapElement
 
 from ..compose_generator import ComposeGenerator
 
@@ -19,3 +20,38 @@ def test_service_with_environment_list(self):
         self.assertEqual(compose_file.services["frontend"].environment["RACK_ENV"], "development")
         self.assertEqual(compose_file.services["frontend"].environment["SHOW"], "true")
         self.assertIsNone(compose_file.services["frontend"].environment["USER_INPUT"])
+
+    def test_kvp_with_multiple_equals_issue_35(self):
+        """Test for issue #35: KVP strings with multiple '=' should split on first '=' only"""
+        # Test the exact scenario from the issue
+        element = ComposeListOrMapElement("JAVA_OPTS=foo=bar&&baz=buzz")
+        self.assertEqual(element["JAVA_OPTS"], "foo=bar&&baz=buzz")
+
+    def test_kvp_splitting_edge_cases(self):
+        """Test various edge cases for KVP splitting to prevent regression"""
+        test_cases = [
+            # (input_string, expected_key, expected_value)
+            ("KEY=value", "KEY", "value"),
+            ("KEY=value=extra", "KEY", "value=extra"),
+            ("KEY=a=b=c=d", "KEY", "a=b=c=d"),
+            ("URL=http://example.com:8080/path?param=value", "URL", "http://example.com:8080/path?param=value"),
+            ("CONFIG=key1=val1,key2=val2", "CONFIG", "key1=val1,key2=val2"),
+            ("COMPLEX=a=b&c=d&e=f", "COMPLEX", "a=b&c=d&e=f"),
+            ("NO_VALUE", "NO_VALUE", None),
+        ]
+
+        for input_string, expected_key, expected_value in test_cases:
+            with self.subTest(input=input_string):
+                element = ComposeListOrMapElement(input_string)
+                self.assertEqual(element[expected_key], expected_value)
+
+    def test_empty_value_handling(self):
+        """Test handling of empty values - this is existing behavior that should be preserved"""
+        # EMPTY= should result in None (existing behavior)
+        element = ComposeListOrMapElement("EMPTY=")
+        self.assertIsNone(element["EMPTY"])
+
+        # Test the isValueEmpty method directly
+        element_test = ComposeListOrMapElement(None)
+        self.assertTrue(element_test.isValueEmpty("KEY="))
+        self.assertFalse(element_test.isValueEmpty("KEY=value"))