EMMA is an open-source toolkit that measures and reports the percentage of Java code covered by unit tests.
EMMA features at a glance:
- EMMA can instrument classes for coverage either offline (before they are loaded) or on the fly (using an instrumenting application classloader).
- Supported coverage types: class, method, line, basic block. EMMA can detect when a single source code line is covered only partially.
- Coverage stats are aggregated at method, class, package, and "all classes" levels.
- Output report types: plain text, HTML, XML. All report types support drill-down, to a user-controlled detail depth. The HTML report supports source code linking.
- Output reports can highlight items with coverage levels below user-provided thresholds.
- Coverage data obtained in different instrumentation or test runs can be merged together.
- Starting with build 2.1.5320 it is possible to dump or reset coverage data remotely and without a JVM exit.
- EMMA does not require access to the source code and degrades gracefully with decreasing amount of debug information available in the input classes.
- EMMA can instrument individual .class files or entire .jars (in place, if desired). Efficient coverage subset filtering is possible, too.
- Makefile and ANT build integration are supported on equal footing.
- EMMA is quite fast: the runtime overhead of added instrumentation is small (5-20%) and the bytecode instrumentor itself is very fast (mostly limited by file I/O speed). Memory overhead is a few hundred bytes per Java class.
- EMMA is 100% pure Java, has no external library dependencies, and works in any Java 2 JVM (even 1.2.x).
