net.jqwik.api.statistics

Class Statistics

java.lang.Object

net.jqwik.api.statistics.Statistics

@API(status=MAINTAINED,
     since="1.2.3")
public class Statistics
extends java.lang.Object

This class serves as a container for static methods to collect statistical data about generated values within a property method and to check coverage of that data.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Statistics.StatisticsFacade

Method Summary

Modifier and Type	Method and Description
static void	collect(java.lang.Object... values) Call this method to record an entry for statistical data about generated values.
static void	coverage(java.util.function.Consumer<StatisticsCoverage> checker) Perform coverage checking for successful property on statistics for values collected with collect(Object...)
static StatisticsCollector	label(java.lang.String label) Call this method to get a labeled instance of StatisticsCollector.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

collect

public static void collect(java.lang.Object... values)

Call this method to record an entry for statistical data about generated values. As soon as this method is called at least once in a property method, the statistical data will be reported after the property has finished.

Usually you call collect(Object[]) method with all arbitraries (parameters passed to test) and than you use coverage(Consumer) method to ensure that certain count of some value has been tried.

NOTE: you can give descriptive name to some collections using label(String) method. Usually you make multiple label+collect calls, i.e. for each passed arbitrary parameter. This way you can provide parameters with descriptive names/labels.

Complete documentation is found at the jqwik documentation page for Checking Coverage of Collected Statistics.

Simple example:

 @Property(generation = GenerationMode.RANDOMIZED)
 void labeledStatistics(@ForAll @IntRange(min = 1, max = 10) Integer anInt) {
        String range = anInt < 3 ? "small" : "large";
        Statistics.label("range").collect(range);
        Statistics.label("value").collect(anInt);

        Statistics.label("range).coverage(
                coverage -> coverage.check("small").percentage(p -> p > 20.0)
         );
        Statistics.label("value").coverage(
                coverage -> coverage.check(0).count(c -> c > 0)
         );
 }
 

Parameters:

values - Can be anything. The list of these values is considered a key for the reported table of frequencies. Constraints:

• There must be at least one value
• The number of values must always be the same in a single property
• Values can be null

Throws:

java.lang.IllegalArgumentException - if one of the constraints on values is violated

See Also:

label(String)

label

public static StatisticsCollector label(java.lang.String label)

Call this method to get a labeled instance of StatisticsCollector.

Parameters:

label - The label will be used for reporting the collected statistical values

See Also:

javadoc of the collect(Object...) method for example usage

coverage

@API(status=EXPERIMENTAL,
     since="1.2.3")
public static void coverage(java.util.function.Consumer<StatisticsCoverage> checker)

Perform coverage checking for successful property on statistics for values collected with collect(Object...)

Sample usage:

 Statistics.coverage(coverage -> coverage.check("small").percentage(p -> p > 20.0));
 Statistics.coverage(coverage -> coverage.check(0).count(c -> c > 0));
 

Parameters:

checker - Code that consumes a StatisticsCoverage object

See Also:

javadoc of the collect(Object...) method for example usage