JUnit Testing Framework Overview for Better Code Quality

JUnit Test Options JUnit Testing Framework TestRunners Test Cases and Test Suites Test Fixtures Objectives:

What is Unit Testing? • Writing tests for small, discretely-defined portions of code • Run and Analyze the Tests • Make it part of Development Process • Run on a Regular Basis • Result is better confidence in the quality of Code

Why Unit Test? • Increase Robustness of your Code • Reduce the time and cost of delivering a system • Measure your progress of development • Early discovery of regressions • Identify unintended side effects • Focus your development effort

What is JUnit? • Open source framework for unit testing written by Erich Gamma and Kent Beck. • Assertions for testing expected results • Test fixtures for sharing common test data • Test suites for easily organizing and running tests • Based on Annotations • Textual test runner • org.junit.runner.JUnitCore

JUnit Goals • Provide a framework that encourages developers to write tests • Overcome the “lack of time” argument • Use familiar tools • Create tests that retain their value over time • Test should be reusable by others • Leverage existing tests to create new ones • Test Fixtures

Writing Testing Code • Debugger Statements • Runtime Expressions • Print Statements • Test Scripts • Tests as Objects • Familiar to Developers • Established Methodology

Writing a Test Case • Steps for running a Test Case using JUnit • Define a class to contain test methods • Annotate test methods with @Test • To check a value, call assertTrue() and pass a boolean that is true if the test succeeds

Simple Test Case import java.util.*; import org.junit.Test; import static org.junit.Assert.*; public class MathTest { @Test public void addition() { double result= 3 + 2; assertTrue(result == 5.0); } }

Alternative Ways to Execute the Test • Test Suite import org.junit.runner.*; import org.junit.runners.*; import static org.junit.runners.Suite.*; @RunWith(value=Suite.class) @SuiteClasses(value={MathTest.class}) public class AllTests { ... // this class can be empty }

TestCase Lifecycle • Methods marked with @Before • Invoked prior to each test • Methods marked with @After • Invoked after each test • For each test method in a TestCase class, the JUnit framework performs these basic steps: • Create a new instance of the TestCase class • Invoke @Before method(s) of the TestCase • Invoke the test method • Invoke @After method(s) of the TestCase • Release the reference to the TestCase instance, which then becomes garbage

Class Scoped set-up and tear-down • static methods marked with @BeforeClass • Run exactly once before all the test methods in the class run • static methods marked with @AfterClass • Run exactly once after all the test methods in the class run • For expensive initializations and clean-ups • Database connections • Network connections • Instead of re-creating before each and every test, create it only once and tear it down once • Test cases can run much faster

Fixtures • Used to establish baseline testing environment • Can be shared by many different tests and test cases. • To create a fixture: • Create a TestCase class • Add an instance variable for each part of the fixture • Provide @Before method to initialize the variables • Provide @After method to release any permanent resources you allocated in initialization

Fixture Example import java.util.*; import org.junit.*; import static org.junit.Assert.*; public class MathTest { protected double fVal1; protected double fVal2; @Before public void setUp() { fVal1 = 2.0; fVal2 = 3.0; } @Test public void addition() { double result= fVal1 + fVal2; assertTrue(result == 5.0); } }

Test Code • Contained within test cases • Test methods must be public, must take no arguments, and must return void. • Typically named testXXX public void testEmptyCollection(){} public void testOneItemCollection(){}

Determining Success or Failure • Part of testing is to run and analyze the test to determine success or failure • Assert Methods throw AssertionError • assertEquals() • assertTrue() • assertNotNull() • Several overloaded versions in org.junit.Assert • Uncaught exceptions are captured by test runner

Testing Exceptions • Use annotation to declare expected exceptions • If exception is not thrown (or a different exception is thrown), the test will fail. @Test(expected=ArithmeticException.class) public void divideByZero() { int n = 2/0; }

Ignored Tests • Use annotation to declare ignored tests • For excessively complex or slow tests not currently required @Ignore public void testInternet() { // screenscrape all web pages }

Timed Tests • Use annotation to declare timeout parameter • If test takes longer than the specified number of milliseconds to run, the test fails. @Test(timeout=500) public void retrieveData() { // database access }

Test Design • Create Repeatable Tests • Run Unit Test after code modification • Guard against regressions • “code a little, test a little” • Write tests as you develop • Write tests to help you debug • Constantly check your tests against your code

What to test • Critical Areas of your code • Parts that are most likely to break • get/set methods? • Forwarding methods? • JSP with no business logic? • Refactored Code • Code that changes the value of an object or creates some kind of side effect.

Test Suite • Runs more than one test at the same time • Programmatic container for TestCase classes • Runs test cases as a logical group • Can contain other TestSuites

Creating a Test Suite import org.junit.runner.*; import org.junit.runners.*; import static org.junit.runners.Suite.*; @RunWith(value=Suite.class) @SuiteClasses(value={MathTest.class, AnotherTest.class}) public class AllTests { @BeforeClass public static void… ... @AfterClass public static void… }

Test Runner - JUnitCore • Executes tests • Text output • Period (.) indicates passed test • .E indicates failed test • .I indicates ignored test • JUnitCore will run any number of test classes java –classpath .;junit-4.4.jar org.junit.runner.JUnitCore TestA TestB TestC

Test Runner Output • Text Output

Summary • Test Options • JUnit Testing Framework • TestRunners • Test Cases and Test Suites • Test Fixtures

JUnit Testing Framework Overview for Better Code Quality

Télécharger la présentation

Plus de contenu associé