Document default behaviour of DataJpaTest#showSql

Closes gh-25843

spring-boot-project/spring-boot-docs/src/docs/asciidoc/spring-boot-features.adoc

@@ -6912,6 +6912,9 @@ TIP: Sometimes writing Spring WebFlux tests is not enough; Spring Boot can help
 You can use the `@DataJpaTest` annotation to test JPA applications.
 By default, it scans for `@Entity` classes and configures Spring Data JPA repositories.
 If an embedded database is available on the classpath, it configures one as well.
+SQL queries are logged by default by setting the `spring.jpa.show-sql` property to `true`.
+This can be disabled using the `showSql()` attribute of the annotation.
+
 Regular `@Component` and `@ConfigurationProperties` beans are not scanned when the `@DataJpaTest` annotation is used.
 `@EnableConfigurationProperties` can be used to include `@ConfigurationProperties` beans.
 

spring-boot-project/spring-boot-test-autoconfigure/src/main/java/org/springframework/boot/test/autoconfigure/orm/jpa/DataJpaTest.java

@@ -53,6 +53,10 @@ import org.springframework.transaction.annotation.Transactional;
  * {@link AutoConfigureTestDatabase @AutoConfigureTestDatabase} annotation can be used to
  * override these settings.
  * <p>
+ * SQL queries are logged by default by setting the {@code spring.jpa.show-sql} property
+ * to {@code true}. This can be disabled using the {@link DataJpaTest#showSql() showSql}
+ * attribute.
+ * <p>
  * If you are looking to load your full application configuration, but use an embedded
  * database, you should consider {@link SpringBootTest @SpringBootTest} combined with
  * {@link AutoConfigureTestDatabase @AutoConfigureTestDatabase} rather than this