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Introduction

Emma is an open source code coverage tool. In our case, Emma enables code coverage by instrumenting the target code. The instrumentation process involves Emma looking at the class or jar files and adding its own layer between the JVM and the code normally called.

During the Instrumenting process, metadata is created per class. This metadata is stored in files locally. In our situation, we generate one meta file per webapp.
The instrumented code has an extra port open, which can accept commands from Emma such as return coverage information or reset coverage information that resides in memory.

To generate a full report Emma requires:

  1. the code has been compiled with the debug option on
  2. the source code is available,
  3. session data is available in a local file,
  4. a relevant metadata file exists.

Command line recipe

Prerequisite

  • The highest version (build 2.1.5320) emma jar file needs to be downloaded from Emma home. The jar needs to be placed in {$JAVA_HOME}/jre/lib/ext or added to the classpath of the following commands. This is also true for the JAVA_HOME seen by the Sakai server.
  • the source code is available for report generation
    Note: I have written a simple Perl script that copies all the source code into one directory
    structure instead of being scattered under the java/src directories. This allows report generation for all reports to point to the same source code directory.
  • Javac compiles the source code with debug option on
    Note: Running maven pack-demo compiles with debug on by default

Instrument code

Once emma.jar sits in the appropriate directory then the following command should bring up the help information for EMMA:

{$JAVA_HOME}/bin/java emma

Resulting output
emma usage: emma <command> command options,
  where <command> is one of:

   run     application runner same as 'emmarun' tool;
   instr   offline instrumentation processor;
   ctl     remote control processor;
   merge   offline data file merge processor.
   report  offline report generator;

  use '<command> -h' to see usage help for a given command

EMMA v2.1, build 5320 (stable)

Note: Any older version than that mentioned in the results will not function correctly for our needs.
Note: I have written some example only Perl code that looks for Web-INF/classes directories and
then generates a bash script that runs Emma and generates a metadata file, one per Webapp

Generate report

Reset in memory coverage session data

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