Download presentation
Presentation is loading. Please wait.
Published byKeaton Plock Modified over 9 years ago
1
1 Unit Testing with JUnit CS 3331 Fall 2009 Kent Beck and Eric Gamma. Test Infected: Programmers Love Writing Tests, Java Report, 3(7):37-50, 1998. Available from: http://junit.sourceforge.net/doc/testinfected/testing.htm
2
2 Unit Testing Introduction Conventional approach Unit testing with JUnit More on JUnit
3
3 Testing in General Testing A way of showing the correctness of software Phases Unit testing To test each module (unit, or component) independently Mostly done by developers of the modules Integration and system testing To test the system as a whole Often done by separate testing or QA team Acceptance testing To validate system functions for (and by) customers or user
4
4 What Is Unit Testing? Definition Testing is the process of showing that a program works for certain inputs. A unit is a module or a small set of modules. In Java, a unit is a class or interface, or a set of them, e.g., An interface and 3 classes that implement it, or A public class along with its helper classes. Unit testing is testing of a unit.
5
5 Question Do you get more confidence by running more test data?
6
6 Why Unit Testing? Code isn’t right if it’s not tested. Practical Most programmers rely on testing, e.g., Microsoft has 1 tester per developer. You could get work as a tester. Divide-and-conquer approach Split system into units. Debug unit individually. Narrow down places where bugs can be. Don’t want to chase down bugs in other units.
7
7 Why Unit Testing? (Cont.) Support regression testing So can make changes to lots of code and know if you broke something. Can make big changes with confidence.
8
8 How to Do Unit Testing Build systems in layers Starts with classes that don’t depend on others. Continue testing building on already tested classes. Benefits Avoid having to write (test) stubs. When testing a module, ones it depends on are reliable.
9
9 Question How does low coupling help testing? How does high coupling hurt it?
10
10 Program to Test public final class IMath { /** * Returns an integer approximation to the square root of x. */ public static int isqrt(int x) { int guess = 1; while (guess * guess < x) { guess++; } return guess; }
11
11 Conventional Testing /** A class to test the class IMath. */ public class IMathTestNoJUnit { /** Runs the tests. */ public static void main(String[] args) { printTestResult(0); printTestResult(1); printTestResult(2); printTestResult(3); printTestResult(4); printTestResult(7); printTestResult(9); printTestResult(100); } private static void printTestResult(int arg) { System.out.print(“isqrt(“ + arg + “) ==> “); System.out.println(IMath.isqrt(arg)); }
12
12 Conventional Test Output Isqrt(0) ==> 1 Isqrt(1) ==> 1 Isqrt(2) ==> 2 Isqrt(3) ==> 2 Isqrt(4) ==> 2 Isqrt(7) ==> 3 Isqrt(9) ==> 3 Isqrt(100) ==> 10 What does this say about the code? Is it right? What’s the problem with this kind of test output?
13
13 Solution? Automatic verification by testing program Can write such a test program by yourself, or Use a testing tool such as JUnit. JUnit A simple, flexible, easy-to-use, open-source, and practical unit testing framework for Java. Can deal with a large and extensive set of test cases. Refer to www.junit.org.
14
14 Testing with JUnit import junit.framework.*; /** A JUnit test class to test the class IMath. */ public class IMathTest extends TestCase { /** Tests isqrt. */ public void testIsqrt() { assertEquals(0, IMath.isqrt(0)); // line 23 assertEquals(1, IMath.isqrt(1)); assertEquals(1, IMath.isqrt(2)); assertEquals(1, IMath.isqrt(3)); assertEquals(2, IMath.isqrt(4)); assertEquals(2, IMath.isqrt(7)); assertEquals(3, IMath.isqrt(9)); assertEquals(10, IMath.isqrt(100)); }
15
15 Testing with JUnit (Cont.) /** Returns the test suite for this test class. */ public static Test suite() { return new TestSuite(IMathTest.class); } /** Run the tests. */ public static void main(String[] args) { junit.textui.TestRunner.run(suite()); // junit.swingui.TestRunner.run(suite()); }
16
16 Compilation and Output $ javac IMath.java IMathTest.java $ java IMathTest.F Time: 0.02 There was 1 failure: 1)testIsqrt(IMathTest)junit.framework.AssertionFailedError: expected: but was: at IMathTest.testIsqrt(IMathTest.java:23) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMeth... at sun.reflect.Delegating... at IMathTest.main(IMathTest.java:17) FAILURES!!! Tests run: 1, Failures: 1, Errors: 0 Question: Is this better? Why?
17
17 Exercise Write a JUnit test class for testing public class ForYou { /** Return the minimum of x and y. */ public static int min(int x, int y) {... } }
18
18 Exercise (Cont.) By filling in the following: import junit.framework.*; /** Test ForYou. */ public class ForYouTest extends TestCase { /** Test min. */ public void testMin() { } // the rest as before … } public class ForYou { /** Return the minimum of x and y. */ public static int min(int x, int y) {... } }
19
19 Some Terminology Definition A test data (or case) for a method M is a pair of (o, args), where o is not null and M can be sent to o, args is a tuple of arguments that can be passed to M. A test data, (o, args), for M succeeds iff o.M(args) behaves as expected. A test data, (o, args), for M fails iff it does not behave as expected. Question Why should o not be null? If M has a bug that is revealed by a test data, does that test data for M succeeds or fails?
20
20 Parts of Test Code Definition The test fixture is the set of variables used in testing. The test driver is the class that runs the tests. The test oracle for a test data is the code that decides success or failure for that test data. Question What in the code we saw so far was the test driver, and the oracle? What difference is there between JUnit testing and non-JUnit testing in what we saw before?
21
21 Basic Usage of JUnit To test a type T: 1. Write a class like: import junit.framework.*; /** A JUnit test class for the class T. */ public class TTest extends TestCase { /** Runs the tests. */ public static void main(String[] args) { junit.textui.TestRunner.run(suite()); } /** Returns the test suite for this test class. */ public static Test suite() { return new TestSuite(TTest.class); } }
22
22 Basic Usage of JUnit (Cont.) 2. Compile T.java and TTest.java $ javac T.java TTest.java 3. Run the JUnit graphical user interface on TTest $ java junit.swingui.TestRunner TTest or Run the text interface (good from makefiles) $ java TTest 4. Look at the failures and errors
23
23 Naming Convention Test methods start with “test” e.g., testIsqrt, testMin Test classes end with “Test” e.g., IMathTest, ForYouTest
24
24 Assertion Methods Method Description assertEquals(a,b)Test if a is equal to b assertFalse(a)Test if a is false assertNotSame(a, b)Test if a and b do not refer to the identical object assertNull(a)Test if a is null assertSame(a,b)Test if a and b refer to the identical object assertTrue(a)Test if a is true - Static methods defined in junit.framework.Assert - Variations taking string error messages
25
25 More on JUnit -- Test Fixture Sharing test data among test methods public class TTest extends TestCase { // other methods here … protected void setUp() throws Exception { // initialize test fixture variables. } protected void tearDown() throws Exception { // uninitialize test fixture variables. } // test fixture variables, i.e., fields shared by several test methods. }
26
26 Example public class PointTest extends TestCase { private Point p; // test fixture variable protected void setUp() { // initializes text fixture variables p = new Point(10, 10); } protected void tearDown() { } // clean up text fixture variables public void testSetX() { // tests SetX p.setX(20); assertEquals(20, p.getX()); } public void testSetY() { // tests SetY p.setY(30); assertEquals(30, p.getY()); } // template and other test methods here… }
27
27 More on JUnit -- Test Suite Definition A test suite is a set of test methods and other test suites. Test Suite Organize tests into a larger test set. Help with automation of testing.
28
28 Example public class AllTestSuite extends TestCase { /** Returns the test suite for this test class. */ public static Test suite() { TestSuite suite = new TestSuite() { public String toString() { return "Test suite for Project T"; } }; suite.addTestSuite(T1Test.class); suite.addTestSuite(T2Test.class); … suite.addTestSuite(TnTest.class); return suite; } // the rest of methods as before … }
29
29 More on JUnit? Refer to www.junit.org JUnit APIs available from the course Web page
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.