CodeTools proposal: "JCov"

Kevin Looney kevin.looney at
Wed Feb 26 14:21:54 PST 2014

Name: JCov

Summary: A code coverage tools, used to measure test coverage on the 
Java platform.

Proposed by: Kevin Looney


This proposal is to open the JCov code coverage tool into the CodeTools 
project of OpenJDK. The goal is to provide transparency to the process 
of gathering coverage metrics during OpenJDK regression testing.

The main motivation is transparency for test coverage metrics. The 
advantage to promoting standard coverage based on JCov is that JDK 
developers will be able to use a code coverage tool that stays in 'lock 
step' with Java language and VM developments.

JCov (Java code COVerage) is a pure Java implementation of a code 
coverage tool which provides a means to measure and analyze dynamic code 
coverage of Java programs. JCov provides functionality to collect 
method, linear block and branch coverage, as well as showing uncovered 
execution paths.

Jcov is also able to show a program's source code annotated with 
coverage information. It also has features to report on the modified 
lines in a changeset. This makes it attractive to incorporate into the 
OpenJDK code review process.

 From a testing perspective, JCov is most useful to determine execution 
paths (in a Java application) that a test suite is (or is not) executing.

JCov supports applications on JDK 1.0 and higher (including JDK 8), 
CDC/CLDC 1.0 and higher, and JavaCard 3.0 and higher.

Other open source Java code coverage tools exist.  They are typically 
not suitable because:

a.) they do not support the current level of the JDK for which coverage 
is being gathered

b.) they do not provide instrumentation to support the coverage of the 
JDK itself.

c.) they do not provide a method to gather coverage data from a device 
across a network.

d.) they do not provide a method to aggregate coverage collections from 
concurrent JVMs.

kevin.looney at

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