Package net.jqwik.api.statistics

Class 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.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method 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​(@Nullable
                           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)