Add schema tests (#1260)

[gjvoosten]

These tests pass against 3.0.4 but fail against 3.0.5.

[stevehu]

Yes, the root cause of the issue described in GitHub Issue #1260 #1260 is a set of syntax errors in the
user's JSON Schema that were previously ignored silently in v3.0.4 but are correctly rejected in v3.0.5 .
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Root Cause Analysis

1. Misplacement of allOf inside properties

In the user's schema:

"questions": {
  "properties": {
    "allOf": [
      { "$ref": "#/$defs/questions" },
      { "assessmentDate": "#/$defs/question" },
      { "expirationDate": "#/$defs/question" }
    ]
  }
}

Because "allOf" is defined inside the "properties" block of "questions" , the validator treats "allOf" as a property name rather than the JSON Schema allOf
keyword.

According to the JSON Schema specification, the schema for any property under "properties" must be a valid JSON Schema (which can only be a JSON object or a
boolean). Because the value of the "allOf" property here is an array ( [...] ), the validator throws:

│ SchemaException: Schema at […]/allOf must be object or boolean but was ARRAY

2. Invalid Subschema syntax

Furthermore, inside the array, they wrote:

{ "assessmentDate": "#/$defs/question" }

This is also invalid JSON Schema syntax (it is an object using a custom property key assessmentDate with a string value, rather than a proper {"$ref": ...}
schema object).
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Why it worked in v3.0.4 but fails in v3.0.5

• In v3.0.4 : The library did not validate loaded schema node types at compilation/load time. Because the input JSON never actually contained a property named
"allOf" , the validator never had to run validation on it, and the schema compiled without crashing.
• In v3.0.5 (introduced by PR #1250): The library added strict compile-time validation of loaded schemas in SchemaRegistry.validateSchemaNodeType . This ensures
that schemas are structurally valid when compiled. Since the value of the property "allOf" is an array, the validator correctly rejects it with a SchemaException
during initialization.
──────

How to Fix the Schema

The user's schema should be corrected to place allOf as a sibling keyword of properties rather than nesting it inside, and specify the subschemas correctly:

 "questions": {
-  "properties": {
-    "allOf": [
-      {
-        "$ref": "#/$defs/questions"
-      },
-      {
-        "assessmentDate": "#/$defs/question"
-      },
-      {
-        "expirationDate": "#/$defs/question"
-      }
-    ]
-  },
+  "allOf": [
+    {
+      "$ref": "#/$defs/questions"
+    },
+    {
+      "properties": {
+        "assessmentDate": {
+          "$ref": "#/$defs/question"
+        }
+      }
+    },
+    {
+      "properties": {
+        "expirationDate": {
+          "$ref": "#/$defs/question"
+        }
+      }
+    }
+  ],
   "required": [
     "assessmentDate"
   ]
 }