Polish "Add config property for KafkaAdmin modifyTopicConfigs"

See gh-31679

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/kafka/KafkaPropertiesTests.java

@@ -21,12 +21,14 @@ import java.util.Map;
 import org.apache.kafka.common.config.SslConfigs;
 import org.junit.jupiter.api.Test;
 
+import org.springframework.boot.autoconfigure.kafka.KafkaProperties.Admin;
 import org.springframework.boot.autoconfigure.kafka.KafkaProperties.Cleanup;
 import org.springframework.boot.autoconfigure.kafka.KafkaProperties.IsolationLevel;
 import org.springframework.boot.autoconfigure.kafka.KafkaProperties.Listener;
 import org.springframework.boot.context.properties.source.MutuallyExclusiveConfigurationPropertiesException;
 import org.springframework.core.io.ClassPathResource;
 import org.springframework.kafka.core.CleanupConfig;
+import org.springframework.kafka.core.KafkaAdmin;
 import org.springframework.kafka.listener.ContainerProperties;
 
 import static org.assertj.core.api.Assertions.assertThat;
@@ -51,6 +53,14 @@ class KafkaPropertiesTests {
 		assertThat(original).hasSize(IsolationLevel.values().length);
 	}
 
+	@Test
+	void adminDefaultValuesAreConsistent() {
+		KafkaAdmin admin = new KafkaAdmin(Map.of());
+		Admin adminProperties = new KafkaProperties().getAdmin();
+		assertThat(admin).hasFieldOrPropertyWithValue("fatalIfBrokerNotAvailable", adminProperties.isFailFast());
+		assertThat(admin).hasFieldOrPropertyWithValue("modifyTopicConfigs", adminProperties.isModifyTopicConfigs());
+	}
+
 	@Test
 	void listenerDefaultValuesAreConsistent() {
 		ContainerProperties container = new ContainerProperties("test");