Polish

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/system/OutputCapture.java

@@ -126,9 +126,7 @@ class OutputCapture implements CapturedOutput {
 	}
 
 	private String get(Predicate<Type> filter) {
-		Assert.state(!this.systemCaptures.isEmpty(),
-				"No system captures found. Check that you have used @RegisterExtension "
-						+ "or @ExtendWith and the fields are not private");
+		Assert.state(!this.systemCaptures.isEmpty(), "No system captures found. Check that you have used @ExtendWith.");
 		StringBuilder builder = new StringBuilder();
 		for (SystemCapture systemCapture : this.systemCaptures) {
 			systemCapture.append(builder, filter);

spring-boot-project/spring-boot-tools/spring-boot-test-support/src/main/java/org/springframework/boot/testsupport/system/OutputCapture.java

@@ -113,9 +113,7 @@ class OutputCapture implements CapturedOutput {
 	}
 
 	private String get(Predicate<Type> filter) {
-		Assert.state(!this.systemCaptures.isEmpty(),
-				"No system captures found. Check that you have used @RegisterExtension "
-						+ "or @ExtendWith and the fields are not private");
+		Assert.state(!this.systemCaptures.isEmpty(), "No system captures found. Check that you have used @ExtendWith.");
 		StringBuilder builder = new StringBuilder();
 		for (SystemCapture systemCapture : this.systemCaptures) {
 			systemCapture.append(builder, filter);