private static Constructor<?> getOnlyConstructor(Class<?> testClass) {
        Constructor<?>[] constructors = testClass.getConstructors();
        if (constructors.length != 1) {
            log.warn("Test class can only have one public constructor, "
                    + "see org.junit.runners.Parameterized.TestClassRunnerForParameters.validateConstructor(List<Throwable>)");
        }
        return constructors[0];
    }
Returns the ScenarioBase instance of this rule
jgiven-junit/src/main/java/com/tngtech/jgiven/junit/JGivenMethodRule.java