update maven-surefire-plugin
diff --git a/pom.xml b/pom.xml
index f94c529..ede6a06 100644
--- a/pom.xml
+++ b/pom.xml
@@ -229,6 +229,11 @@
 					<encoding>${file_encoding}</encoding>
 				</configuration>
 			</plugin>
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-surefire-plugin</artifactId>
+				<version>2.21.0</version>
+			</plugin>
 		</plugins>
 	</build>