add unit test for part_has_slices function

craft_parts/parts.py

@@ -101,7 +101,7 @@ def validate_root(cls, values: Dict[str, Any]) -> Dict[str, Any]:
 
         # Detect a mixture of .deb packages and chisel slices.
         stage_packages = values.get("stage-packages", [])
-        has_slices = part_has_slices(values)
+        has_slices = any(name for name in stage_packages if is_slice(name))
         has_packages = any(name for name in stage_packages if not is_slice(name))
 
         if has_slices and has_packages:
@@ -166,6 +166,15 @@ def has_overlay(self) -> bool:
             or self.overlay_files != ["*"]
         )
 
+    @property
+    def has_slices(self) -> bool:
+        """Whether the part has slices in its stage-packages.
+
+        :param data: The part data to query.
+        """
+        stage_packages = self.stage_packages or []
+        return any(name for name in stage_packages if is_slice(name))
+
 
 # pylint: disable=too-many-public-methods
 class Part:
@@ -639,15 +648,6 @@ def part_has_overlay(data: Dict[str, Any]) -> bool:
     return spec.has_overlay
 
 
-def part_has_slices(data: Dict[str, Any]) -> bool:
-    """Whether the part described by ``data`` has slices in its stage-packages.
-
-    :param data: The part data to query.
-    """
-    stage_packages = data.get("stage-packages", [])
-    return any(name for name in stage_packages if is_slice(name))
-
-
 def is_slice(name: str) -> bool:
     """Whether the stage-package is a slice or a package.
 

tests/unit/test_parts.py

@@ -339,6 +339,18 @@ def test_part_has_overlay(self, partitions):
         p = Part("foo", {}, partitions=partitions)
         assert p.has_overlay is False
 
+    @pytest.mark.parametrize(
+        ("tc_spec", "tc_result"),
+        [
+            ({}, False),
+            ({"stage-packages": ["libc6_libs"]}, True),
+            ({"stage-packages": ["python3"]}, False),
+        ],
+    )
+    def test_part_has_slices(self, partitions, tc_spec, tc_result):
+        p = Part("foo", tc_spec, partitions=partitions)
+        assert p.spec.has_slices == tc_result
+
 
 class TestPartOrdering:
     """Test part ordering.