Add test from Appendix C. Example of recursive schema extension of the draft.

Author: olegshtch

remotes/tree.json

@@ -0,0 +1,16 @@
+{
+    "description": "tree schema, extensible",
+    "$id": "http://localhost:1234/tree.json",
+    "$dynamicAnchor": "node",
+
+    "type": "object",
+    "properties": {
+        "data": true,
+        "children": {
+            "type": "array",
+            "items": {
+                "$dynamicRef": "#node"
+            }
+        }
+    }
+}

tests/draft-future/dynamicRef.json

@@ -441,5 +441,35 @@
                 "valid": true
             }
         ]
+    },
+    {
+        "description": "strict-tree schema, guards against misspelled properties",
+        "schema": {
+            "$id": "http://localhost:1234/strict-tree.json",
+            "$dynamicAnchor": "node",
+
+            "$ref": "tree.json",
+            "unevaluatedProperties": false
+        },
+        "tests": [
+            {
+                "description": "instance with misspelled field",
+                "data": {
+                    "children": [{
+                            "daat": 1
+                        }]
+                },
+                "valid": false
+            },
+            {
+                "description": "instance with correct field",
+                "data": {
+                    "children": [{
+                            "data": 1
+                        }]
+                },
+                "valid": true
+            }
+        ]
     }
 ]

tests/draft2020-12/dynamicRef.json

@@ -441,5 +441,35 @@
                 "valid": true
             }
         ]
+    },
+    {
+        "description": "strict-tree schema, guards against misspelled properties",
+        "schema": {
+            "$id": "http://localhost:1234/strict-tree.json",
+            "$dynamicAnchor": "node",
+
+            "$ref": "tree.json",
+            "unevaluatedProperties": false
+        },
+        "tests": [
+            {
+                "description": "instance with misspelled field",
+                "data": {
+                    "children": [{
+                            "daat": 1
+                        }]
+                },
+                "valid": false
+            },
+            {
+                "description": "instance with correct field",
+                "data": {
+                    "children": [{
+                            "data": 1
+                        }]
+                },
+                "valid": true
+            }
+        ]
     }
 ]