Add unit tests for cn.iocoder.common.framework.util.DateUtil

These tests were written using Diffblue Cover.

common/common-framework/pom.xml

@@ -74,6 +74,12 @@
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>
         </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.8.1</version>
+            <scope>test</scope>
+        </dependency>
 
     </dependencies>