private void validateEnvelope(JsonNode env) {
        assertNotNull(env);
        assertTrue(env.isObject());
        assertEquals(2, env.size());
        assertTrue(env.has(JsonSchema.ENVELOPE_SCHEMA_FIELD_NAME));
        assertTrue(env.get(JsonSchema.ENVELOPE_SCHEMA_FIELD_NAME).isObject());
        assertTrue(env.has(JsonSchema.ENVELOPE_PAYLOAD_FIELD_NAME));
    }
When schemas are disabled, fields are mapped to Connect maps.
connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java