[s3] fix race condition in test

Signed-off-by: Andrea Cioni <supercionci@hotmail.it>

Author: andreacioni

spring-batch-s3/src/test/java/org/springframework/batch/extensions/s3/stream/S3MultipartOutputStreamTests.java

@@ -32,6 +32,7 @@
 import static org.mockito.BDDMockito.given;
 import static org.mockito.BDDMockito.then;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.timeout;
 
 class S3MultipartOutputStreamTests {
 
@@ -61,7 +62,7 @@ void testWriteSingleByteTriggersUpload() throws IOException {
 			ArgumentCaptor<InputStream> captor = ArgumentCaptor.forClass(InputStream.class);
 
 			// then
-			then(this.multipartUploadMock).should().upload(captor.capture());
+			then(this.multipartUploadMock).should(timeout(1000L)).upload(captor.capture());
 			assertThat(captor.getValue().available()).as("InputStream should contain one byte").isEqualTo(1);
 		}
 	}