JSON schema test (see https://json-schema-faker.js.org/#gist/76c65d9f6ec6ec56e14cf7a366778996)

base

{
  "id": "base",
  "properties": {
    "prop1": {
      "type": "number"
    },
    "prop2": {
      "type": "number"
    },
    "prop_obj": {
      "type": "object",
      "properties": {
        "sprop1": {
          "type": "number"
        },
        "sprop2": {
          "type": "number"
        }
      }
    }
  }
}

event

{
  "allOf": [
    {
      "$ref": "base"
    }
  ],
  "properties": {
    "prop3": {
      "type": "number"
    },
    "prop1": {
      "const": "val"
    },
    "prop_obj": {
      "type": "object",
      "properties": {
        "sprop1": {
          "const": "sprop_val"
        }
      }
    }
  }
}