Re: [Cobertura-devel] How does Cobertura count branches?

[Roger B. <ro...@ro...>]

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On 07/03/12 12:39, Kevin Bedard wrote:
> Hello.  Are branches counted by counting the newline chars in my code?
> Or does it count the statement separators?  Or other?

It works on the bytecode, not the source and does both line and branch
based coverage.  Use 'javap' on a .class file to see what the insides look
like (before you have run Cobertura on it).

The line based coverage merely checks that for any line that has
corresponding bytecode, any of that bytecode has been executed.

> If (exp1) or (exp2) then action1;

The bytecode for that line looks something like this:

  evaluate exp1
  if true goto body
  evaluate exp2
  if false goto end
  :body
  evaluate action1
  :end

If exp1 was always true then the exp2 bit is never executed.  Branch
reporting would look at the above byte code and see that there are 2 gotos
and check that they are both executed.  (I don't know exactly what it does
behind the scenes - that is the principle to make sure all the bytecode is
executed.)

> How does Cobertura report coverage on such a statement?

Look at the top of the HTML report.  There is one column for line coverage
and one column for branch coverage.

In the listing lines where all the code has been executed are shown with a
green margin.  Lines where not all branches have been taken are
highlighted in a pinkish red.

Roger
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