Unit TestingUnit Testing

TopicsTopics

• Motivation• JUnit framework• Basic JUnit tests – static methods• Ensure exceptions thrown• @Before and @BeforeClass –

instance methods• Test floating point values

JUnit MotivationJUnit Motivation• Goal: relieve human from task of comparing

expected and actual values

public class Utilities {public static int calcPerimeter(int length, int width)

{ return 2 * (length + width); }

public static void main(String [] args) { // Ensure output is 16 System.out.println(Utilities.calcPerimeter(2,6)); }

}

Test-Driven Development (TDD)Test-Driven Development (TDD)

1. Add a test (or tests) for an new unit of functionality (unit === method)

2. Run prior tests, see new test fail– may write stubs so code compiles

3. Implement new functionality4. Run tests, see them succeed5. Refactor – clean code rocks!6. Repeat

Tests FirstTests First

• Some “easy” examples– How would you test a function to

calculate the area of a triangle?– How would you test a function to

calculate the circumference of a circle?– How would you test a function that

calculates wind chill?

JUnit FrameworkJUnit Framework• Test Case. Method that runs one or more

tests. • Test Suite. Collection of tests run at the

same time. Includes one or more test cases/methods.

• Test Runner. Utility used to run a test suite. – In Eclipse, shows a graphical presentation. – May also be a command-line version (Ruby).

• JUnit framework available from http://junit.org

Packages in JavaPackages in Java

• A package is a way to bundle classes by functionality

Customers don’t really want to see all your test code!

Create a PackageCreate a Package

In Eclipse:• Create a Java project, click on src• Select new package icon• Enter an appropriate name• For this example, create a package

named windchill*• Select the package, create a new

class named MyTempConverter

* for distribution, you’d want to ensure uniquehttp://www.efsavage.com/blog/posts/java_package_conventions/

More on PackagesMore on Packages

• The package statement must be the first line in the file, e.g.:package windchill;

public class MyTempConverter {

…

}

• Each package has its own directory (in the file structure)

TDD Example: WindchillTDD Example: Windchill

See the formula and chart:http://www.nws.noaa.gov/om/windchill/index.shtml

Windchill formula:• 35.74 + 0.6215T - 35.75V (**0.16) + 0.4275TV(**0.16)

The TempConverter classThe TempConverter class

• First we create the “failing” methods – so that our tests will at least compile

package windchill;

public class MyTempConverter {

public static long windChill(int speed, int temperature){ return -1;}

}

Why does it make sense for this method to be static?

Adding the testsAdding the tests

• Create a package for your tests• Add your test classes to the package

– Select the test package– Create a new class of type JUnit Test

Case

Eclipse and JUnitEclipse and JUnit

1. Select JUnit Test Case 2. Select JUnit Test Case

We’ll use JUnit 4Pick a meaningful name

click

Eclipse and JUnit continuedEclipse and JUnit continued

Dialog for class to test:You must type in packageThen you’ll see possible classes

Eclipse prompts for libraryEclipse prompts for library

Build PathBuild PathIf Eclipse creates a JUnit test for you, you’ll be prompted to add library.To add a library later:

Right-click on project name (in package explorer)Select Build PathSelect Add Libraries

Select JUnit 4

JUnit v4JUnit v4

• New Java Feature: annotations• Places a “marker” in code that is

interpreted by another tool• For JUnit, marker/annotation is @Test• No need to extend TestCase (JUnit3)• Must import org.junit.*;

Some windchill testsSome windchill testspackage tests;

import junit.framework.Assert;

import static org.junit.Assert.*;

import Windchill.MyTempConverter;

public class TestWindchillCalcs {

@Test

public void testWindchill()

{

long expected = -11;

long actual = MyTempConverter.windChill(5, 0);

assertEquals(expected, actual);

// local variables not needed

assertEquals(3, MyTempConverter.windChill(10, 15));}

}

The TempConverter classThe TempConverter class

• Now add code so that the tests pass

package Windchill;

public class MyTempConverter {

public static long windChill(int speed, int temperature){ double newTemp = 35.74 + 0.6215*temperature - 35.75 * Math.pow(speed, 0.16) + 0.4275 * temperature * Math.pow(speed,0.16); return Math.round(newTemp);}

public static void main(String[] args) { System.out.println(MyTempConverter.windChill(10, 30));

}

}

Run as JUnit TestRun as JUnit Test

JUnit ExecutionJUnit Execution

All is well!

Error! Look at failure trace for explanation

Can also test for expected exceptionsCan also test for expected exceptionspackage Windchill;

public class BadInputException extends RuntimeException {public BadInputException() {}

public BadInputException(String msg){ super(msg); }}

@Test (expected = BadInputException.class)public void testWindchillLowSpeed() throws BadInputException{ long actual = MyTempConverter.windChill(4, 10);}

public static long windChill(int speed, int temperature){if (speed < 5) throw new BadInputException("Windchill not valid if speed < 5");double newTemp = 35.74 + 0.6215*temperature - 35.75 * Math.pow(speed, 0.16) + 0.4275 * temperature * Math.pow(speed,0.16);return Math.round(newTemp);}

Exception class

JUnit test

Discuss with a partnerDiscuss with a partner

• When would we need the throws clause on the test?

• What happens if the (expected) phrase is removed?

Testing instance methodsTesting instance methods• When testing a class that has instance methods

(most often), the test will need to create an instance

• @BeforeClass and @AfterClass annotated methods will be run exactly once during your test run - at the very beginning and end of the test as a whole, before anything else is run. In fact, they're run before the test class is even constructed, which is why they must be declared static.

• The @Before and @After methods will be run before and after every test case, so will probably be run multiple times during a test run

Example to illlustrate @BeforeExample to illlustrate @Before

package game;

public class Location {

private int x, y;

public void move(int dx, int dy)

{

x += dx;

y += dy;

}

// Also has constructors and getters

}

Test it – see @Before messageTest it – see @Before messagepublic class TestLocation {

private Location location;

@Before

public void setUp(){

System.out.println("In @Before"); location = new Location();

}

@Test

public void testMove() {

location.move(5, 10);

assertEquals(5, location.getX());

assertEquals(10, location.getY());

}

@Test

public void testMove2() {

location.move(5, 10);

assertEquals(5, location.getX());

assertEquals(10, location.getY());

location.move(5, 10);

assertEquals(10, location.getX());

assertEquals(20, location.getY());

}

}

Example of @BeforeClassExample of @BeforeClass• Assume the board set up is complex, and

you don’t need to reset between tests.

package game;

public class Board { private String gameStatus;

public void init() { gameStatus = "Long game set up is done!"; } public String getGameStatus() { return gameStatus; }

}

The @BeforeClass testThe @BeforeClass testimport game.Board;

public class TestBoard {

static Board board;

@BeforeClass

public static void setUpBeforeClass() throws Exception {

System.out.println("In @BeforeClass");

board = new Board();

board.init();

}

@Test

public void test1() {

assertEquals(board.getGameStatus(), "Long game set up is done!");

}

@Test

public void test2() {

assertEquals(board.getGameStatus(), "Long game set up is done!");

}

}

}

@BeforeClass not run for each test instance – just the entire test suite – so variables must be static

This is an advanced detail – will not be covered on tests, BUT may be helpful in your projects

Testing floating pointsTesting floating points• Remember that floating point values should not be

compared exactly. public class MyConverter {

public static double INCHES_TO_METERS = 0.0254;

public static double englishToMeters(int feet, int

inches)

{

return 0;

//int totalInches = feet * 12 + inches;

//return totalInches * INCHES_TO_METERS;

}

}

The testThe test• Use a tolerance

public class TestConversions {

public static double EPSILON = .0001;

@Test

public void testFeetToMeters()

{

double expected = 0.0508;

double actual = MyConverter.englishToMeters(0, 2);

assertEquals(expected, actual, EPSILON);

expected = 0.3556;

actual = MyConverter.englishToMeters(1, 2);

assertEquals(expected, actual, EPSILON);

}

What tests could you write for…What tests could you write for…

• A chess game• A linked list library• String library• UPC code

Advanced TopicAdvanced Topic• The static import construct allows unqualified access to static members

import static org.junit.Assert.assertEquals;

@Test

public void testMove3() {

location.move(5, 10);

assertEquals(5, location.getX());

assertEquals(10, location.getY());

}