diff --git a/.travis.yml b/.travis.yml
index 91cce0cef6..4f7be19fc7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -7,6 +7,7 @@ sudo: required
 
 cache:
   directories:
+    - $HOME/.m2
     - $HOME/downloads
 
 branches:
@@ -37,6 +38,9 @@ script:
       mvn test -P tinkerpop-process-test,$BACKEND
     fi
 
+after_success:
+  - bash <(curl -s https://codecov.io/bash)
+
 jobs:
   include:
     - stage: deploy
@@ -47,7 +51,6 @@ jobs:
         - |
           if [ $DEPLOYED = 0 ]; then
             DEPLOYED=1
-            mvn cobertura:cobertura > /dev/null && bash <(curl -s https://codecov.io/bash)
             mvn clean package -DskipTests
           else
             echo "Skipping before_deploy since it has been executed once."
diff --git a/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java b/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java
index db55235042..ae8c80b974 100644
--- a/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java
+++ b/hugegraph-cassandra/src/main/java/com/baidu/hugegraph/backend/store/cassandra/CassandraTable.java
@@ -27,8 +27,12 @@
 import java.util.Map;
 import java.util.Set;
 
+import org.apache.commons.lang3.ObjectUtils;
+import org.apache.http.client.utils.CloneUtils;
+import org.apache.lucene.queryparser.xml.QueryBuilderFactory;
 import org.slf4j.Logger;
 
+import com.baidu.hugegraph.HugeException;
 import com.baidu.hugegraph.backend.BackendException;
 import com.baidu.hugegraph.backend.id.Id;
 import com.baidu.hugegraph.backend.query.Condition;
diff --git a/hugegraph-core/src/main/java/com/baidu/hugegraph/util/CopyUtil.java b/hugegraph-core/src/main/java/com/baidu/hugegraph/util/CopyUtil.java
index 69cf2fbafc..52f2b5b382 100644
--- a/hugegraph-core/src/main/java/com/baidu/hugegraph/util/CopyUtil.java
+++ b/hugegraph-core/src/main/java/com/baidu/hugegraph/util/CopyUtil.java
@@ -19,6 +19,7 @@
 
 package com.baidu.hugegraph.util;
 
+import java.lang.reflect.Array;
 import java.lang.reflect.Field;
 import java.lang.reflect.Modifier;
 
@@ -33,27 +34,40 @@ public static <T> T cloneObject(T o, T clone) throws Exception {
         }
         for (Field field : o.getClass().getDeclaredFields()) {
             field.setAccessible(true);
-            Object childObj = field.get(o);
-            if (childObj == null || Modifier.isFinal(field.getModifiers())) {
+            Object value = field.get(o);
+            if (value == null || Modifier.isFinal(field.getModifiers())) {
                 continue;
             }
 
             Class<?> declareType = field.getType();
-            Class<?> valueType = childObj.getClass();
+            Class<?> valueType = value.getClass();
             if (ReflectionUtil.isSimpleType(declareType) ||
                 ReflectionUtil.isSimpleType(valueType)) {
-                field.set(clone, field.get(o));
+                field.set(clone, value);
+            } else if (declareType.isArray() && valueType.isArray() &&
+                       valueType.getComponentType().isPrimitive()) {
+                field.set(clone, cloneArray(value));
             } else {
-                if (childObj == o) {
+                if (value == o) {
                     field.set(clone, clone);
                 } else {
-                    field.set(clone, cloneObject(field.get(o), null));
+                    field.set(clone, cloneObject(value, null));
                 }
             }
         }
         return clone;
     }
 
+    private static Object cloneArray(Object value) {
+        Class<?> valueType = value.getClass();
+        assert valueType.isArray() &&
+               valueType.getComponentType().isPrimitive();
+        int len = Array.getLength(value);
+        Object array = Array.newInstance(valueType.getComponentType(), len);
+        System.arraycopy(value, 0, array, 0, len);
+        return array;
+    }
+
     public static <T> T copy(T object) {
         return copy(object, null);
     }
diff --git a/hugegraph-dist/pom.xml b/hugegraph-dist/pom.xml
index 990022930e..f555eda2ad 100644
--- a/hugegraph-dist/pom.xml
+++ b/hugegraph-dist/pom.xml
@@ -165,5 +165,4 @@
             </plugin>
         </plugins>
     </build>
-
-</project>
\ No newline at end of file
+</project>
diff --git a/hugegraph-test/pom.xml b/hugegraph-test/pom.xml
index 5cf6edba6b..e28c95686b 100644
--- a/hugegraph-test/pom.xml
+++ b/hugegraph-test/pom.xml
@@ -12,11 +12,47 @@
     <artifactId>hugegraph-test</artifactId>
 
     <dependencies>
+        <!-- Jacoco report-aggregate just statistics its directly dependent module,
+             so must explicitly import each submodule -->
+        <dependency>
+            <groupId>com.baidu.hugegraph</groupId>
+            <artifactId>hugegraph-core</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <!-- The hugegraph-api module was not added because the module's test needs to
+             embed the bytecode before starting the service, but did not find a suitable
+             way to write the script to start the service -->
+        <dependency>
+            <groupId>com.baidu.hugegraph</groupId>
+            <artifactId>hugegraph-cassandra</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.baidu.hugegraph</groupId>
+            <artifactId>hugegraph-scylladb</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.baidu.hugegraph</groupId>
+            <artifactId>hugegraph-rocksdb</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.baidu.hugegraph</groupId>
+            <artifactId>hugegraph-hbase</artifactId>
+            <version>${project.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>com.baidu.hugegraph</groupId>
+            <artifactId>hugegraph-mysql</artifactId>
+            <version>${project.version}</version>
+        </dependency>
         <dependency>
             <groupId>com.baidu.hugegraph</groupId>
             <artifactId>hugegraph-dist</artifactId>
             <version>${project.version}</version>
         </dependency>
+
         <dependency>
             <groupId>org.apache.tinkerpop</groupId>
             <artifactId>gremlin-test</artifactId>
@@ -35,134 +71,143 @@
     </dependencies>
 
     <build>
-        <pluginManagement>
-            <plugins>
-                <plugin>
-                    <groupId>org.apache.maven.plugins</groupId>
-                    <artifactId>maven-surefire-plugin</artifactId>
-                    <version>2.20</version>
-                    <executions>
-                        <execution>
-                            <id>core-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/CoreTestSuite.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                        <execution>
-                            <id>unit-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/UnitTestSuite.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                        <execution>
-                            <id>api-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/ApiTestSuite.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                        <execution>
-                            <id>tinkerpop-structure-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/StructureStandardTest.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                        <execution>
-                            <id>tinkerpop-process-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/ProcessStandardTest.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                        <execution>
-                            <id>tinkerpop-structure-perf-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/StructurePerformanceTest.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                        <execution>
-                            <id>tinkerpop-process-perf-test</id>
-                            <configuration>
-                                <testSourceDirectory>${basedir}/src/main/java/
-                                </testSourceDirectory>
-                                <testClassesDirectory>${basedir}/target/classes/
-                                </testClassesDirectory>
-                                <includes>
-                                    <include>**/ProcessPerformanceTest.java</include>
-                                </includes>
-                            </configuration>
-                        </execution>
-                    </executions>
-                </plugin>
-                <plugin>
-                    <artifactId>maven-clean-plugin</artifactId>
-                    <version>3.0.0</version>
-                    <configuration>
-                        <filesets>
-                            <fileset>
-                                <directory>${top.level.dir}</directory>
-                                <excludes>
-                                    <exclude>${final.name}/**</exclude>
-                                    <exclude>*.tar.gz</exclude>
-                                    <exclude>*.zip</exclude>
-                                    <exclude>*.tar</exclude>
-                                </excludes>
-                                <followSymlinks>false</followSymlinks>
-                            </fileset>
-                            <fileset>
-                                <directory>${final.name}</directory>
-                            </fileset>
-                        </filesets>
-                    </configuration>
-                </plugin>
-                <plugin>
-                    <groupId>org.codehaus.mojo</groupId>
-                    <artifactId>cobertura-maven-plugin</artifactId>
-                    <version>2.7</version>
-                    <configuration>
-                        <formats>
-                            <format>html</format>
-                            <format>xml</format>
-                        </formats>
-                        <check />
-                    </configuration>
-                </plugin>
-            </plugins>
-        </pluginManagement>
+        <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>2.20</version>
+                <executions>
+                    <execution>
+                        <id>core-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/CoreTestSuite.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>unit-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/UnitTestSuite.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>api-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/ApiTestSuite.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>tinkerpop-structure-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/StructureStandardTest.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>tinkerpop-process-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/ProcessStandardTest.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>tinkerpop-structure-perf-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/StructurePerformanceTest.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                    <execution>
+                        <id>tinkerpop-process-perf-test</id>
+                        <configuration>
+                            <testSourceDirectory>${basedir}/src/main/java/
+                            </testSourceDirectory>
+                            <testClassesDirectory>${basedir}/target/classes/
+                            </testClassesDirectory>
+                            <includes>
+                                <include>**/ProcessPerformanceTest.java</include>
+                            </includes>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <artifactId>maven-clean-plugin</artifactId>
+                <version>3.0.0</version>
+                <configuration>
+                    <filesets>
+                        <fileset>
+                            <directory>${top.level.dir}</directory>
+                            <excludes>
+                                <exclude>${final.name}/**</exclude>
+                                <exclude>*.tar.gz</exclude>
+                                <exclude>*.zip</exclude>
+                                <exclude>*.tar</exclude>
+                            </excludes>
+                            <followSymlinks>false</followSymlinks>
+                        </fileset>
+                        <fileset>
+                            <directory>${final.name}</directory>
+                        </fileset>
+                    </filesets>
+                </configuration>
+            </plugin>
+            <plugin>
+                <groupId>org.jacoco</groupId>
+                <artifactId>jacoco-maven-plugin</artifactId>
+                <version>0.8.3</version>
+                <executions>
+                    <execution>
+                        <id>pre-test</id>
+                        <goals>
+                            <goal>prepare-agent</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>post-test</id>
+                        <phase>test</phase>
+                        <goals>
+                            <goal>report-aggregate</goal>
+                        </goals>
+                        <configuration>
+                            <outputDirectory>${basedir}/../target/site/jacoco</outputDirectory>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
 
         <resources>
             <resource>
@@ -244,4 +289,4 @@
             </properties>
         </profile>
     </profiles>
-</project>
\ No newline at end of file
+</project>