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quick_check

For a description of this example, please see the comments in the quick_check.lgt and tests.lgt source files.

For more information on QuickCheck-based testing see the documentation of the lgtunit tool.

See also the testing and `tests_dsl examples.

Print Logtalk, Prolog backend, and kernel versions (if running as a notebook):

%versions

Start by loading the sample properties used to use QuickCheck interactively at the top-level interpreter:

logtalk_load(quick_check(loader)).

Ensure that QuickCheck warnings are printed:

set_logtalk_flag(report, warnings).

Check that reversing a list twice gives back the same list:

lgtunit::quick_check(reverse_2_twice_prop(+list)).

Check the same_length_2_prop/1 property by running the default number of random tests:

lgtunit::quick_check(same_length_2_prop(+list)).

Check the same_length_3_prop/1 property by running 25 random tests:

lgtunit::quick_check(same_length_3_prop(+list), [n(25)]).

Try a broken property, broken_nth1_3_prop/1, to check returning of a counter-example that falsifies the property:

lgtunit::quick_check(broken_nth1_3_prop(+list), [n(25)]).

<!--

quick check test failure (at test 1 after 0 shrinks):
broken_nth1_3_prop([]) false. -->
The alternative `lgtunit::quick_check/3` predicate returns results in reified form:
```
lgtunit::quick_check(same_length_2_prop(+list), Result, []).
```

```
lgtunit::quick_check(broken_nth1_3_prop(+list), Result, [n(250)]).
```


Defining a predicate specifying a property of the predicate that we want to test is not always necessary; for example assuming that the predicate length/2 is defined in user:
```
lgtunit::quick_check(length(+list, -integer)).
```


The template of the quick_check/1-3 predicates can also use the (::)/2 and (<<)/2 control constructs:
```
lgtunit::quick_check(list::length(+list, -integer)).
```

```
lgtunit::quick_check(list<<length(+list, -integer)).
```


When using a backend Prolog system supporting modules, the template argument of the quick_check/1-3 predicates can be an explicitly module-qualified template; for example, assuming a system providing a lists module defining the de facto standard length/2 predicate:
```
use_module(library(lists)).
```

```
lgtunit::quick_check(lists:length(+list, -integer)).
```