test_cover.pl -- Clause coverage 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 for which the head unification succeeded. For each clause we count how often it succeeded and how often it failed. In addition we track all call sites, creating goal-by-goal annotated clauses.

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.

show_coverage(:Goal) is semidet

show_coverage(:Goal, +Options) is semidet

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

Report on coverage by Goal. Goal is executed as in once/1. Options processed:

modules(+Modules)

Provide a detailed report on Modules. For backwards compatibility this is the same as providing a list of modules in the second argument.

annotate(+Bool)

Create an annotated file for the detailed results. This is implied if the ext or dir option are specified.

ext(+Ext)

Extension to use for the annotated file. Default is `.cov`.

dir(+Dir)

Dump the annotations in the given directory. If not given, the annotated files are created in the same directory as the source file. Each clause that is related to a physical line in the file is annotated with one of:

###	Clause was never executed.
++N	Clause was entered N times and always succeeded
--N	Clause was entered N times and never succeeded
+N-M	Clause has succeeded N times and failed M times
+N*M	Clause was entered N times and succeeded M times

All call sites are annotated using the same conventions, except that --- is used to annotate subgoals that were never called.

line_numbers(Boolean)

If true (default), add line numbers to the annotated file.

color(Boolean)

Controls using ANSI escape sequences to color the output in the annotated source. Default is true.

report_hook(+Succeeded, +Failed) is semidet[multifile]

This hook is called after the data collection. It is passed a list of objects that have succeeded as well as a list of objects that have failed. The objects are one of

ClauseRef: The specified clause
call_site(ClauseRef, PC, PI): A call was make in ClauseRef at the given program counter to the predicate indicated by PI.

Undocumented predicates

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

show_coverage(Arg1, Arg2)