[java code coverage] Jacoco Coverage issue with Junit Parallel Execution

[causalbody]

Hi Guys, 
I am seeing significant variations in jacoco coverage report for the same set 
of integration tests run in "parallel" vs "sequential". Coverage percentages 
below.

Maven : 2.x 

Sequential:
INSTRUCTION     7%      
BRANCH  3%      
COMPLEXITY      6%      
LINE    7%      
METHOD  10%     
CLASS   18%


Parallel:
INSTRUCTION     2%      
BRANCH  1%      
COMPLEXITY      1%      
LINE    2%      
METHOD  2%      
CLASS   8%      



<plugin>
                                                
<artifactId>maven-failsafe-plugin</artifactId>
                                                <version>2.20.1</version>
                                                <dependencies> 
                                                <dependency>
                                                    
<groupId>org.apache.maven.surefire</groupId> 
                                                    
<artifactId>surefire-junit47</artifactId>
                                                    <version>2.20.1</version>
                                                </dependency> 
                                            </dependencies> 
                                                <executions>
                                                        <execution>
                                                                
<id>default-test</id>
                                                                
<phase>integration-test</phase>
                                                                <goals>
                                                                        
<goal>integration-test</goal>
                                                                        
<goal>verify</goal>
                                                                </goals>
                                                        </execution>
                                                </executions>
                                                <configuration>
                                                        <argLine>-Xms1024m 
-Xmx3072m</argLine>
                                                        
<trimStackTrace>false</trimStackTrace>
                                                        
<skipTests>false</skipTests>
                                                    <parallel>classes</parallel>
                                                        
<threadCount>30</threadCount>
                                                        
<perCoreThreadCount>true</perCoreThreadCount>
                                                        <includes>
                                                                
<include>**/*Test.java</include>
                                                        </includes>
....
</plugin>


jacoco config (using offline instrumentation for JMockit based unit tests and 
java agent for integration tests)

<plugin>
<!--                            Create/generate the application.html using 
xsltproc -->
                                <groupId>org.jacoco</groupId>
                                <artifactId>jacoco-maven-plugin</artifactId>
                                <version>0.7.9</version>
                                <executions>
                                        <execution>
                                                <id>instrument</id>
                                                <phase>process-classes</phase>
                                                <goals>
                                                        <goal>instrument</goal>
                                                </goals>
                                        </execution>
                                        <execution>
                                                <id>restore</id>
                                                <phase>prepare-package</phase>
                                                <goals>
                                                        
<goal>restore-instrumented-classes</goal>
                                                </goals>
                                        </execution>
                                        <execution>
                                                <id>it-bind-agent</id>
                                                <goals>
                                                        
<goal>restore-instrumented-classes</goal>
                                                        
<goal>prepare-agent-integration</goal>
                                                </goals>
                                        </execution>
                                        <execution>
                                                <id>ut-report</id>
                                                <goals>
                                                        <goal>report</goal>
                                                </goals>
                                        </execution>
                                        <execution>
                                                <id>it-report</id>
                                                <goals>
                                                        
<goal>report-integration</goal>
                                                </goals>
                                        </execution>
                                </executions>
                        </plugin>  

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