@Test
    public void testCacheSchemaToConnectConversion() {
        assertEquals(0, converter.sizeOfToConnectSchemaCache());

        converter.toConnectData(TOPIC, "{ \"schema\": { \"type\": \"boolean\" }, \"payload\": true }".getBytes());
        assertEquals(1, converter.sizeOfToConnectSchemaCache());

        converter.toConnectData(TOPIC, "{ \"schema\": { \"type\": \"boolean\" }, \"payload\": true }".getBytes());
        assertEquals(1, converter.sizeOfToConnectSchemaCache());

        // Different schema should also get cached
        converter.toConnectData(TOPIC, "{ \"schema\": { \"type\": \"boolean\", \"optional\": true }, \"payload\": true }".getBytes());
        assertEquals(2, converter.sizeOfToConnectSchemaCache());

        // Even equivalent, but different JSON encoding of schema, should get different cache entry
        converter.toConnectData(TOPIC, "{ \"schema\": { \"type\": \"boolean\", \"optional\": false }, \"payload\": true }".getBytes());
        assertEquals(3, converter.sizeOfToConnectSchemaCache());
    }
When schemas are disabled, fields are mapped to Connect maps.
connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java