Add Hypothesis strategies for registries and resources

pyproject.toml

@@ -44,7 +44,10 @@ Changelog = "https://referencing.readthedocs.io/en/stable/changes/"
 Source = "https://github.com/python-jsonschema/referencing"
 
 [dependency-groups]
-dev = ["pytest>9"]
+dev = [
+  "hypothesis>=6.100",
+  "pytest>9",
+]
 docs = [
   "furo",
   "pygments-github-lexers",

referencing/tests/strategies.py

@@ -0,0 +1,45 @@
+"""Hypothesis strategies for exercising registries and resources."""
+
+from __future__ import annotations
+
+from typing import Any
+
+from hypothesis import strategies as st
+
+from referencing import Registry, Resource
+
+json_values = st.recursive(
+    st.none() | st.booleans() | st.integers() | st.text(),
+    lambda children: (
+        st.lists(children, max_size=3)
+        | st.dictionaries(st.text(), children, max_size=3)
+    ),
+    max_leaves=10,
+)
+"""A strategy producing JSON-compatible values."""
+
+uris = st.text(
+    alphabet=st.characters(blacklist_categories=("Cs",)),
+    min_size=1,
+    max_size=20,
+).map(lambda path: f"urn:example:{path}")
+"""A strategy producing non-empty opaque resource identifiers."""
+
+
+@st.composite
+def resources(draw: st.DrawFn) -> Resource[Any]:
+    """Generate an opaque resource containing a JSON-compatible value."""
+    return Resource.opaque(draw(json_values))
+
+
+@st.composite
+def registries(draw: st.DrawFn) -> Registry[Any]:
+    """Generate a registry containing zero or more opaque resources."""
+    pairs = draw(
+        st.lists(
+            st.tuples(uris, resources()),
+            max_size=5,
+            unique_by=lambda pair: pair[0],
+        ),
+    )
+    return Registry().with_resources(pairs)

referencing/tests/test_strategies.py

@@ -0,0 +1,18 @@
+from hypothesis import given, settings
+
+from referencing.tests.strategies import registries, resources
+
+
+@settings(max_examples=25)
+@given(resources())
+def test_resources_are_opaque(resource):
+    assert resource.id() is None
+    assert list(resource.subresources()) == []
+    assert list(resource.anchors()) == []
+
+
+@settings(max_examples=25)
+@given(registries())
+def test_registries_contain_unique_resource_uris(registry):
+    assert len(registry) == len(set(registry))
+    assert all(registry[uri].id() is None for uri in registry)