@Test
    public void timeToConnectOptionalWithDefaultValue() {
        java.util.Date reference = new java.util.Date(0);
        Schema schema = Time.builder().optional().defaultValue(reference).schema();
        String msg = "{ \"schema\": { \"type\": \"int32\", \"name\": \"org.apache.kafka.connect.data.Time\", \"version\": 1, \"optional\": true, \"default\": 0 }, \"payload\": null }";
        SchemaAndValue schemaAndValue = converter.toConnectData(TOPIC, msg.getBytes());
        assertEquals(schema, schemaAndValue.schema());
        assertEquals(reference, schemaAndValue.value());
    }
When schemas are disabled, fields are mapped to Connect maps.
connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java