java - What are the differences between the three methods of code coverage analysis?

Question

This sonar page basically lists the various methods employed by different code coverage analysis tools:

1. Source code instrumentation(Used by Clover)
2. Offline byte code instrumentation(Used by Cobertura)
3. On-the-fly byte code instrumentation(Used by Jacoco)

What are these three methods and which one is the most efficient and why?If the answer to the question of efficiency is "it depends" , then please explain why?

Answer 1

Source code instrumentation consists in adding instructions to the source code before compiling it. These instructions are used to trace which parts of the codes have been executed.

Offline byte-code instrumentation consists in adding those same instructions, but after the compilation, directly into the byte-code.

On-the-fly byte-code instrumentation consists in adding those same instructions in the byte-code, but dynamically, at runtime, when the byte-code is loaded by the JVM.

This page has a comparison between the methods. It might be biased, since it's part of the Clover documentation.

Depending on your definition of "efficient", choose the one you like the most. I don't think you'll get enormous differences. They all do the job, and the big picture will be the same whatever the method used.