@Test
    public void testConnectorHasMissingPredicateClass() throws InterruptedException {
        Map<String, String> config = defaultSinkConnectorProps();
        String predicateName = "p";
        config.put(PREDICATES_CONFIG, predicateName);
        config.put(PREDICATES_CONFIG + "." + predicateName + ".type", "WheresTheFruit");
        connect.assertions().assertExactlyNumErrorsOnConnectorConfigValidation(
                config.get(CONNECTOR_CLASS_CONFIG),
                config,
                1,
                "Connector config should fail preflight validation when a predicate with a class not found on the worker is specified",
                0
        );
    }
Integration test for preflight connector config validation
connect/runtime/src/test/java/org/apache/kafka/connect/integration/ConnectorValidationIntegrationTest.java