JCOV
JCov is a pure java implementation of a code coverage tool which provides a means to measure and analyze dynamic code coverage of Java programs.
Preparation
Unfortunately, at the time of writing, the jcov tool is not present in Maven and we need to download and build the project ourselves. Luckily, this is an easy process, and once prepared, the jar file could be reused as many times as wanted.
The following is the procedure to download and build jcov:
export JCOV_HOME=~/jcoverage #Prepare base directory mkdir $JCOV_HOME cd $JCOV_HOME #Build jtreg git clone https://github.com/openjdk/jtreg.git cd jtreg bash make/build.sh --jdk $JAVA_HOME cd - #Build jcov git clone https://github.com/openjdk/jcov.git cd jcov/build #Download dependencies mvn dependency:get -Dartifact=org.ow2.asm:asm:9.1 -Dtransitive=false -Ddest=asm-9.1.jar mvn dependency:get -Dartifact=org.ow2.asm:asm-util:9.1 -Dtransitive=false -Ddest=asm-util-9.1.jar mvn dependency:get -Dartifact=org.ow2.asm:asm-tree:9.1 -Dtransitive=false -Ddest=asm-tree-9.1.jar ant clean ant -v -f build.xml -Dasm.jar=$PWD/asm-9.1.jar -Dasm-util.jar=$PWD/asm-util-9.1.jar -Dasm-tree.jar=$PWD/asm-tree-9.1.jar -Djavatestjar=$JCOV_HOME/jtreg/build/images/jtreg/lib/javatest.jar
Build
With jcov, the classes are instrumented after compilation, so we can build as usual and instrument the jar files later. After a regular compilation, you need to choose the jar files you'd like to use for coverage and instrument them:
mkdir coverage_reports cd coverage_reports #Identify jcov jar file export JCOV_JAR=$JCOV_HOME/jcov/JCOV_BUILD/jcov_3.0/jcov.jar #Instrument java classes find $ACSROOT/lib -name "*.jar" | xargs java -cp $JCOV_JAR:$(acsMakeJavaClasspath -eclipse) com.sun.tdk.jcov.Instr -t coverage_instr.xml
Execute
There are two ways of performing coverage for the executions. One is to run the classes and generate intermediate files that would need to be combined at a later stage and the second is to instance a server that will receive the information from all instrumented Java classes and combine the data on-the-fly.
For simplicity we choose the later:
#Identify jcov jar file export JCOV_JAR=$JCOV_HOME/jcov/JCOV_BUILD/jcov_3.0/jcov.jar cd coverage_reports #Start Grabber nohup java -cp $JCOV_JAR com.sun.tdk.jcov.Grabber -o coverage_result.xml -t coverage_instr.xml & java -cp $JCOV_JAR com.sun.tdk.jcov.GrabberManager -wait
After this we run the application code with a small change:
#Identify jcov jar files export JCOV_JAR=$JCOV_HOME/jcov/JCOV_BUILD/jcov_3.0/jcov.jar export JCOV_SAVER_JAR=$JCOV_HOME/jcov/JCOV_BUILD/jcov_3.0/jcov_network_saver.jar #Option #1 java -cp $JCOV_SAVER_JAR:$CLASSPATH <usual_command> #Option #2 java -javaagent:$JCOV_JAR=grabber <usual_command>
Coverage
After all your tests have been executed with one of the options above, you need to stop the grabber and generate the report:
#Identify jcov jar file export JCOV_JAR=$JCOV_HOME/jcov/JCOV_BUILD/jcov_3.0/jcov.jar cd coverage_reports #Kill Grabber java -cp $JCOV_JAR com.sun.tdk.jcov.GrabberManager -kill #Merge Templates java -cp $JCOV_JAR com.sun.tdk.jcov.Merger -o coverage_merged.xml -t coverage_instr.xml coverage_result.xml
Report
#Identify jcov jar file export JCOV_JAR=$JCOV_HOME/jcov/JCOV_BUILD/jcov_3.0/jcov.jar cd coverage_reports #Generate Report java -cp $JCOV_JAR com.sun.tdk.jcov.RepGen coverage_merged.xml
The result will be a report in XML with the coverage information.