not able to generate coverage.emma file

Question

I am performing code coverage using emma for a simple junit case. I am able to compile,instrument,run the junit case from ant successfully. My issue is, the coverage.emma file is not getting generated which I believe is required to generate the coverage report. Below is message I get:

report: 
[report] processing input files ... 
[report] 1 file(s) read and merged in 10 ms 
[report] nothing to do: no runtime coverage data found in any of the data files 

The junit task is below:

<!-- Run the Juit cases --> 
<target name="runJunit">
    <junit printsummary="on" showoutput="yes" fork="true">
       <test name="com.ea.test.testCode1" />
         <classpath> 
           <pathelement location="${dest.dir}" />
           <pathelement location="C:\junit4.11\junit-4.11.jar" />
         </classpath> 
         <jvmarg value="-XX:-UseSplitVerifier"/> 
         <jvmarg value="-Demma.coverage.out.file=${coverage.dir}/coverage.emma" />                                              
         <jvmarg value="-Demma.coverage.out.merge=false" /> 
    </junit> 
</target>