Implement JSON Merge Patch from IETF RFC 7396

tests/test_utilities.py

@@ -0,0 +1,46 @@
+"""Test the utilities functions."""
+
+import pytest
+
+from openflexure_microscope_server import utilities
+
+
+@pytest.mark.parametrize(
+    ("target", "patch", "outcome", "err_if_enforce"),
+    [
+        ({"a": "b"}, {"a": "c"}, {"a": "c"}, False),
+        ({"a": "b"}, {"b": "c"}, {"a": "b", "b": "c"}, False),
+        ({"a": "b"}, {"a": None}, {}, False),
+        ({"a": "b", "b": "c"}, {"a": None}, {"b": "c"}, False),
+        ({"a": ["b"]}, {"a": "c"}, {"a": "c"}, False),
+        ({"a": "c"}, {"a": ["b"]}, {"a": ["b"]}, False),
+        (
+            {"a": {"b": "c"}},
+            {"a": {"b": "d", "c": None}},
+            {"a": {"b": "d"}},
+            False,
+        ),
+        ({"a": [{"b": "c"}]}, {"a": [1]}, {"a": [1]}, False),
+        (["a", "b"], ["c", "d"], ["c", "d"], True),
+        ({"a": "b"}, ["c"], ["c"], True),
+        ({"a": "foo"}, None, None, True),
+        ({"a": "foo"}, "bar", "bar", True),
+        ({"e": None}, {"a": 1}, {"e": None, "a": 1}, False),
+        ([1, 2], {"a": "b", "c": None}, {"a": "b"}, True),
+        ({}, {"a": {"bb": {"ccc": None}}}, {"a": {"bb": {}}}, False),
+    ],
+)
+def test_merge_patch(target, patch, outcome, err_if_enforce):
+    """Check that merge_patch returns the expected outcome for each target and patch.
+
+    These test cases are specified in Appedix A of IETF RFC 7396.
+    """
+    assert utilities.merge_patch(target, patch) == outcome
+
+    # If expected to error when enforce_dict is True then check:
+    if err_if_enforce:
+        with pytest.raises(ValueError, match="Both target and patch"):
+            utilities.merge_patch(target, patch, enforce_dict=True)
+    else:
+        # Else should run without error with same expected value
+        assert utilities.merge_patch(target, patch, enforce_dict=True) == outcome