🧪 [testing improvement] Add tests for _parameters_by_id in diff.py

contracts/tools/tests/test_pic_diff.py

@@ -1,6 +1,8 @@
 from copy import deepcopy
 
-from pic_contracts.diff import changes_to_markdown, diff_parameters
+import pytest
+
+from pic_contracts.diff import _parameters_by_id, changes_to_markdown, diff_parameters
 
 
 def _doc(value: int = 20) -> dict:
@@ -44,11 +46,49 @@ def test_diff_reports_new_period() -> None:
     )
     after["parameters"][0]["values"][0]["to"] = "2027-01-01"
     changes = diff_parameters(before, after)
-    assert [change.kind for change in changes] == ["removed_period", "new_period", "new_period"]
+    assert [change.kind for change in changes] == [
+        "removed_period",
+        "new_period",
+        "new_period",
+    ]
 
 
 def test_diff_reports_removed_parameter() -> None:
     before = _doc()
     after = {"conformsTo": "pic-parameters/0.1.0", "parameters": []}
     changes = diff_parameters(before, after)
     assert [change.kind for change in changes] == ["removed_parameter"]
+
+
+def test_parameters_by_id_happy_path() -> None:
+    doc = {
+        "parameters": [
+            {"id": "param1", "value": 1},
+            {"id": "param2", "value": 2},
+        ]
+    }
+    result = _parameters_by_id(doc)
+    assert result == {
+        "param1": {"id": "param1", "value": 1},
+        "param2": {"id": "param2", "value": 2},
+    }
+
+
+def test_parameters_by_id_missing_parameters_key() -> None:
+    doc = {"other_key": "value"}
+    assert _parameters_by_id(doc) == {}
+
+
+def test_parameters_by_id_empty_parameters_list() -> None:
+    doc = {"parameters": []}
+    assert _parameters_by_id(doc) == {}
+
+
+def test_parameters_by_id_missing_id_key() -> None:
+    doc = {
+        "parameters": [
+            {"not_id": "param1", "value": 1},
+        ]
+    }
+    with pytest.raises(KeyError):
+        _parameters_by_id(doc)

pr_description.md

@@ -0,0 +1,11 @@
+🎯 **What:** The testing gap addressed
+The `_parameters_by_id` function in `contracts/tools/src/pic_contracts/diff.py` lacked explicit test coverage. This function takes a document dictionary and returns a dictionary mapping parameter IDs to parameter dictionaries.
+
+📊 **Coverage:** What scenarios are now tested
+1. **Happy Path:** Correctly mapping multiple parameters by their IDs.
+2. **Missing Key:** Handling a document without a "parameters" key (returns an empty dictionary).
+3. **Empty List:** Handling a document with an empty "parameters" list (returns an empty dictionary).
+4. **Missing ID:** Ensuring a `KeyError` is raised if a parameter dictionary is missing the "id" key.
+
+✨ **Result:** The improvement in test coverage
+The `_parameters_by_id` function is now fully covered by tests, ensuring its behavior remains correct and deterministic. This prevents regressions if the way parameter IDs are extracted or mapped is changed in the future.