com.carrotsearch.examples.randomizedrunner

Class Test004MoreRandomness

java.lang.Object

com.carrotsearch.examples.randomizedrunner.Test004MoreRandomness

public class Test004MoreRandomness
extends Object

Randomness is entwined everywhere in RandomizedRunner. An instance of Random is of course available from a RandomizedContext, but even tests themselves are randomized, or to be more precise: their order of execution is shuffled.

In this example we have two classes that contain three methods (they're nested under a single suite class for simplicity). Every execution of class Test004MoreRandomness.OrderRandomized will be different, shuffling test methods around (and the random numbers written to the output). We can "pin" the execution order by forcing the master random seed using Seed annotation on the class (or a system property SysGlobals.SYSPROP_RANDOM_SEED). Doing so also fixes all derivative random generators in all tests - this is shown in Test004MoreRandomness.OrderRandomizedButFixed, every execution of this class will be identical (and will emit identical pseudo-random numbers).

All this is meant for one purpose: help in reproducing a failed randomized test case. Once a test case fails, make sure you write down the random seed number that caused the failure and add appropriate Seeds annotation on the method that failed like so:

 @Seeds({
   @Seed("012345"),
   @Seed()
 })
 

where 012345 is the replaced by the seed that caused the failure. This makes the test methods run with a fixed seed once and then with a random seed again, easily creating a new regression test so that the bug does not reoccur in the future. An example of that is shown in Test004MoreRandomness.OrderRegression.regression(). Also note how RandomizedRunner modifies test method names for such "expanded" methods, appending the random seed as a parameter. This is needed to avoid duplicate test Description objects (a design flaw in JUnit). We will see these parameters again in the example concerning parameterized tests.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Test004MoreRandomness.OrderRandomized
static class	Test004MoreRandomness.OrderRandomizedButFixed
static class	Test004MoreRandomness.OrderRegression

Constructor Summary

Constructors

Constructor and Description
Test004MoreRandomness()

Method Summary

Methods inherited from class java.lang.Object

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

Constructor Detail

Test004MoreRandomness

public Test004MoreRandomness()