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Code Coverage with Emma

Olivier from the JDT/Core team has been working on running the Emma code coverage tool on the JDT/Core test suites to get an idea of their coverage. Here are some steps to get the tool running in your workspace. (Olivier did most of the work... we just put it on the wiki :-)



  • Download and extract latest Emma release.
  • Put the contents of the build.xml file below into a file in your workspace.
  • Edit the 3 properties at the top of the file.
    • project.dir - the root directory of the project that you are testing
    • output.dir - the directory where you want your output to go
    • emma.dir - your Emma installation directory


  • Create a new Ant launch configuration called Emma Instrumentation and select the instr target.
  • Run the Emma Instrumentation launch configuration. This will instrument the class files in your output directory.

Run the Tests

Next you want to run your tests and collect the output. There are 2 ways to get the output file in the correct place. You can do either of the following:

  1. Run your test suites with the following System property set: -Demma.coverage.out.file=<output.dir>/ (fill in your output directory).
  2. Run your test suite as per normal and copy the file to your emma_output directory after it is done. (its location will appear in the console)

Create the Report

  • Create a new Ant launch configuration called Emma Create Report and select the report target.
  • Run the Emma Create Report launch configuration. This will generate a report in the output directory. Open the index.html file to start browsing the results.


Some notes and things to think of...

  • Remember to clean your bin/ folder to remove instrumented class files.
  • You may have to expand the export-src Ant call if you have multiple source folders in your project.
  • You will also have to make changes if you have multiple output folders in your project.


These are the contents of the Ant build file that you will be running.

<?xml version="1.0" encoding="UTF-8"?>
<project name="emma" basedir="../../.">

	<!-- What project are you testing? -->
	<property name="project.dir" value="${basedir}/"/>

	<!-- Where should we output the results?-->
	<property name="output.dir" value="D:/temp/emma_output"/>

	<!-- Emma? Where are you? (Emma installation directory)-->
	<property name='emma.dir' value='D:/downloads/emma-2.0.5312' />


	<!-- Where are the class files? -->
	<property name="bin" value="${project.dir}/bin"/>
	<!-- EMMA distribution directory: -->
	<path id='emma.lib' >
		<fileset dir='${emma.dir}' includes='lib/*.jar' />
	<taskdef resource='' classpathref='emma.lib' />

	<!-- Target which instruments the class files -->
	<target name="instr">
		<mkdir dir="${output.dir}"/>
			<!-- instrumentation of bin folder -->
			<instr instrpath="${bin}" mode="overwrite" outfile="${output.dir}/coverage.em"/>
		<!-- copy the emma classes into the bin folder -->
		<unjar dest="${bin}" src="${emma.dir}/lib/emma.jar" overwrite="true"/>

	<!-- This target copies your source files so they can be used for generation of
			the reports later. -->
	<property name="src.dir" value="${output.dir}/src" />
	<target name="export-src">
		<antcall target="cleanup"/>
		<mkdir dir="${src.dir}" />
		<copy todir="${src.dir}">
			<fileset dir="${project.dir}/src">
				<include name="**/*.java"/>

	<!-- Generate the report. -->
	<target name="report">
		<antcall target="export-src"/>
			<!-- creating a report -->
			<report sort="+name,+class,+method,+block" sourcepath="${src.dir}">
				<infileset dir="${output.dir}" includes="*.em, *.ec"/>
				<html outfile="${output.dir}/index.html" depth="method" columns="name,class,method,block,line"/>

	<target name="cleanup">
		<delete dir="${src.dir}" failonerror="false"/>



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