test_cover.pl -- Clause cover analysis

The purpose of this module is to find which part of the program has been used by a certain goal. Usage is defined in terms of clauses that have fired, separated in clauses that succeeded at least once and clauses that failed on each occasion.

This module relies on the SWI-Prolog tracer hooks. It modifies these hooks and collects the results, after which it restores the debugging environment. This has some limitations:

• The performance degrades significantly (about 10 times)
• It is not possible to use the debugger during coverage analysis
• The cover analysis tool is currently not thread-safe.

The result is represented as a list of clause-references. As the references to clauses of dynamic predicates cannot be guaranteed, these are omitted from the result.

bug

- Relies heavily on SWI-Prolog internals. We have considered using a meta-interpreter for this purpose, but it is nearly impossible to do 100% complete meta-interpretation of Prolog. Example problem areas include handling cuts in control-structures and calls from non-interpreted meta-predicates.

To be done

- Provide detailed information organised by predicate. Possibly annotate the source with coverage information.

 show_coverage(:Goal) is semidet

 show_coverage(:Goal, +Modules:list(atom)) is semidet

Report on coverage by Goal. Goal is executed as in once/1. Report the details of the uncovered clauses for each module in the list Modules

 assert_cover(+Port, +Frame) is det[private]

Assert coverage of the current clause. We monitor two ports: the unify port to see which clauses we entered, and the exit port to see which completed successfully.

 running_static_pred(+Frame) is semidet[private]

True if Frame is not running a dynamic predicate.

 assert_entered(+Ref) is det[private]

 assert_exited(+Ref) is det[private]

Add Ref to the set of entered or exited clauses.

 covered(+Ref, +VisibleMask, +LeashMask, -Succeeded, -Failed) is det[private]

Restore state and collect failed and succeeded clauses.

 file_coverage(+Succeeded, +Failed, +Modules) is det[private]

Write a report on the clauses covered organised by file to current output. Show detailed information about the non-coverered clauses defined in the modules Modules.

 clause_source(+Clause, -File, -Line) is det[private]

clause_source(-Clause, +File, -Line) is det[private]

 detailed_report(+Uncovered:list(clause), +Modules:list(atom)) is det[private]

Undocumented predicates

The following predicates are exported, but not or incorrectly documented.

 show_coverage(Arg1, Arg2)