com.carrotsearch.examples.randomizedrunner

Class Test003UsingRandomness

java.lang.Object

org.junit.Assert

com.carrotsearch.randomizedtesting.RandomizedTest

com.carrotsearch.examples.randomizedrunner.Test003UsingRandomness

public class Test003UsingRandomness
extends RandomizedTest

So far we haven't really used the Random provided by RandomizedRunner. The idea behind randomized tests is to, for each test execution:

• cover a possibly different execution path of the tested component,
• cover a different data (input) passed to the tested component,
• execute in a different "environment" if there is environment variability.

Let's see this on a simple example of a method that adds two integers (Test003UsingRandomness.Adder.add(int, int)). We can test this method using a "fixed" test case as shown in fixedTesting() but this test will always execute in an identical way (which is good if you're looking for regression coverage but bad if you want to expand your tested domain).

A randomized test, on the other hand, will pick parameters from a larger spectrum of values and assert on the method's contract. Here, we can make sure the sum is always larger or equal than the arguments given two positive arguments. This assertion will fail quite often because of integer overflows as shown in randomizedTesting() (re-run the test a few times if it doesn't fail the first time).

While the above example is trivial most of the bugs in code stem from similar subtleties (possibly resulting from more complex interactions). In many cases the "contract" that we can assert on can be stated as "throw no-exception" given valid arguments. An example of that is in method expectNoException(). At first glance this method will work most of the time, but try passing Integer.MIN_VALUE as a random number and see what will happen.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Test003UsingRandomness.Adder

Field Summary

Fields inherited from class com.carrotsearch.randomizedtesting.RandomizedTest

ISO8859_1, SYSPROP_MULTIPLIER, US_ASCII, UTF16, UTF32, UTF8

Constructor Summary

Constructors

Constructor and Description
Test003UsingRandomness()

Method Summary

Methods

Modifier and Type	Method and Description
void	expectNoException()
void	fixedTesting()
void	randomizedTesting()

Methods inherited from class com.carrotsearch.randomizedtesting.RandomizedTest

$, $$, assumeFalse, assumeFalse, assumeNoException, assumeNoException, assumeNotNull, assumeTrue, assumeTrue, atLeast, atMost, between, closeAfterSuite, closeAfterTest, frequently, getContext, getRandom, globalTempDir, isNightly, iterations, multiplier, newServerSocket, newTempDir, newTempDir, newTempFile, newTempFile, randomAsciiOfLength, randomAsciiOfLengthBetween, randomBoolean, randomByte, randomDouble, randomFloat, randomFrom, randomFrom, randomGaussian, randomInt, randomInt, randomIntBetween, randomLocale, randomLong, randomRealisticUnicodeOfCodepointLength, randomRealisticUnicodeOfCodepointLengthBetween, randomRealisticUnicodeOfLength, randomRealisticUnicodeOfLengthBetween, randomShort, randomTimeZone, randomUnicodeOfCodepointLength, randomUnicodeOfCodepointLengthBetween, randomUnicodeOfLength, randomUnicodeOfLengthBetween, rarely, scaledRandomIntBetween, sleep, systemPropertyAsBoolean, systemPropertyAsDouble, systemPropertyAsFloat, systemPropertyAsInt, systemPropertyAsLong

Methods inherited from class org.junit.Assert

assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertArrayEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertEquals, assertFalse, assertFalse, assertNotNull, assertNotNull, assertNotSame, assertNotSame, assertNull, assertNull, assertSame, assertSame, assertThat, assertThat, assertTrue, assertTrue, fail, fail

Methods inherited from class java.lang.Object

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

Constructor Detail

Test003UsingRandomness

public Test003UsingRandomness()

Method Detail

fixedTesting

public void fixedTesting()

randomizedTesting

public void randomizedTesting()

expectNoException

public void expectNoException()