@Test
    public void nullSchemaAndPrimitiveToJson() {
        // This still needs to do conversion of data, null schema means "anything goes"
        JsonNode converted = parse(converter.fromConnectData(TOPIC, null, true));
        validateEnvelopeNullSchema(converted);
        assertTrue(converted.get(JsonSchema.ENVELOPE_SCHEMA_FIELD_NAME).isNull());
        assertTrue(converted.get(JsonSchema.ENVELOPE_PAYLOAD_FIELD_NAME).booleanValue());
    }
When schemas are disabled, fields are mapped to Connect maps.
connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java