4.1  Function Coverage

The headers of a test are not just there for decoration; three properties are enforced when a test, say, (*$X foo is compiled, where X is T, R, Q,... :

• foo exists; that is to say, it is defined in the scope of the module where the testappears – though one can play with pragmas to relax this condition somewhat. At the very least, it has to be defined somewhere. Failure to conform results in an Error: Unbound value foo.
• foo is referenced in each statement of the test: for T and Q, that means "each line". For R, that means "once somewhere in the test’s body". Failure to conform results in a Warning 26: unused variable foo, which will be treated as an error if -warn-error +26 is passed to the compiler. It goes without saying that this is warmly recommended.
• the test possesses at least one statement.

Those two conditions put together offer a strong guarantee that, if a function is referenced in a test header, then it is actually tested at least once. The list of functions referenced in the headers of extracted tests is written by qtest into qtest.targets.log. Each line is of the form

foo.ml   42    foo

where foo.ml is the file in which the test appears, as passed to extract, and 42 is the line number where the test pragma appears in foo.ml. Note that a same function can be listed several times for the same source file, if several tests involve it (say, two times if it has both a simple test and a random one). The exact number of statements involving foo in each test is currently not taken into account in the logs.