Unit Testing Bartosz Walter Software Engineering Lecture XXX.

Unit TestingUnit Testing

Bartosz Walter<[email protected]>

Software Engineering Lecture XXX

AgendaAgenda

1. JUnit – a unit testing library for Java2. Guidelines for creating test cases3. Smells in tests4. Implementation tasks

Schemat klas jUnitSchemat klas jUnit

TestCase

Test

TestSuiteTestResult

RomanNumberTest

TestCaseTestCase

MyTestvoid testXXXX()

void tearDown()

void setUp()

junit.framework.TestCase

void testYYYY()

void testZZZZ()

void testWWWW()

void testXXXX()

void testYYYY()

void testZZZZ()

MyTest(name)

StudentTest.java

Klasa i jej klasa testowaKlasa i jej klasa testowa

+ testComputeLevel()

+ testGetAge()

+ testGetName()

+ tearDown()

+ setUp()

+ computeLevel()

+ getAge()

+ getName()

Student.java

Utworzenie instancji klasy Student

Usunięcie instancji klasy Student

– Student student

TestCaseTestCase

MyTestvoid testXXXX()

void tearDown()

void setUp()

junit.framework.TestCase

void testYYYY()

void testZZZZ()

void testWWWW()

void testXXXX()

void testYYYY()

void testZZZZ()

MyTest(name)

Simplest test possible...Simplest test possible...

void tearDown()

void setUp()

void testSimple()

public void setUp() { rn1 = new RomanNumber(5); rn2 = new RomanNumber(20);}

public void testSimple()throws Exception {

String str = rn1.toString(); assertEquals(str, "V");

}

public void tearDown() { rn1 = null; rn2 = null;}

RomanNumberTest(name)public RomanNumberTest(name){ super(name);}

Failure vs. errorFailure vs. error

Failure: anticipated violation of the test assertion signals that the test actually fails

Error: unanticipated exception caught by the test runner the test could not be run properly

Failure vs. errorFailure vs. error

public void testNonexistentFileRead() throws IOException { try { File file = new File("doesNotExist.txt"); FileReader reader = new FileReader(file); assertEquals('a', (char) reader.read()); fail("Read from a nonexistent file?!"); } catch (FileNotFoundException success) {} }

public void testExistingFileRead() throws IOException { // exists.txt created in setup(), perhaps File file = new File("exists.txt"); FileReader reader = new FileReader(file);

assertEquals('a', (char) reader.read()); }

Basic functionality of a Basic functionality of a TestCaseTestCase

Groups of methods: equality tests

void assertEquals([msg], expected, actual) identity tests

void assertSame([msg], expected, actual) void assertNotSame ([msg], expected, actual)

boolean tests void assertTrue([msg], condition) void assertFalse([msg], condition)

null tests void assertNull([msg], object) void assertNotNull([msg], object)

unconditional failure void fail([msg])

Creating Creating TestSuiteTestSuites staticallys statically

public class RomanNumberTest extends TestCase {

public RomanNumberTest(String name) { super(name); }

// testing methods public void testSimpleConv() {} public void testAddition() {}

public static Test suite() { TestSuite suite = new TestSuite(); suite.addTest(new MyTest("testSimpleConv")); suite.addTest(new MyTest("testAddition")); return suite; } }

Creating Creating TestSuiteTestSuites dynamicallys dynamically

public class RomanNumberTest extends TestCase {

public RomanNumberTest(String name) { super(name); }

// testing methods public void testSimpleConv() {} public void testAddition() {}

public static Test suite() { TestSuite suite = new TestSuite(); suite.addTestSuite(MyTest.class) return suite; } }

Guidelines for creating Guidelines for creating TestCaseTestCasess

Don't use constructor for initializing the TestCase

junit.framework.AssertionFailedError: Cannot instantiate test case: test1

at junit.framework.Assert.fail(Assert.java:143) at junit.framework.TestSuite$1.runTest(TestSuite.java:178)at junit.framework.TestCase.runBare(TestCase.java:129) at junit.framework.TestResult$1.protect

(TestResult.java:100) ...

public class SomeTest extends TestCase { public SomeTest (String testName) { super (testName); // Perform test set-up }}

Guidelines for creating Guidelines for creating TestCaseTestCasess

Don't use constructor for initializing the TestCase

public class SomeTest extends TestCase { public SomeTest (String testName) { super (testName); } public void setUp() { // Perform test set-up }}

java.lang.IllegalStateException: Oopsat bp.DTC.setUp(DTC.java:34) at junit.framework.TestCase.runBare(TestCase.java:127)at junit.framework.TestResult$1.protect(

TestResult.java:100) ...

Guidelines for creating TestCasesGuidelines for creating TestCases

Don't assume the order in which tests within a TestCase are executedAvoid writing TestCases with side effects

public class SomeTestCase extends TestCase {

public SomeTestCase (String testName) { super (testName); }

public void testDoThisFirst () { }

public void testDoThisSecond () { } }


Don't assume the order in which tests within a TestCase are executedAvoid writing TestCases with side effects

public class SomeTestCase extends TestCase { public void testDoThisFirst () { }

public void testDoThisSecond () { }

public static Test suite() { suite.addTest(new SomeTestCase("testDoThisFirst";)); suite.addTest(new SomeTestCase("testDoThisSecond";)); return suite; } }


Avoid using hardcoded resourcesWrite self-contained testsPlace tests in the same packages as source code

public class SomeTestCase extends TestCase { public void setUp () { FileInputStream inp ("C:\\TestData\\dataSet1.dat"); // .. }}


Avoid using hardcoded resourcesWrite self-contained testsPlace tests in the same packages as source code

public class SomeTestCase extends TestCase { public void setUp () { InputStream inp = class.getResourceAsStream (this.getClass (), "dataSet1.dat"); }}


Avoid time/locale-sensitive tests

Date date = DateFormat.getInstance().parse("dd/mm/yyyy");

Calendar cal = Calendar.getInstance();Cal.set(yyyy, mm-1, dd);Date date = Calendar.getTime();

Locale locale = Locale.getDefault();


Use JUnit assert/fail methods for throwing ExceptionsDon't catch exceptions unless they are expected to be thrown

public void exampleTest() { try { // do some testing } catch (SomeApplicationException ex) { fail ("Caught SomeApplicationException exception"); }}


public void testIndexOutOfBoundsException() {

ArrayList emptyList = new ArrayList();

try { Object o = emptyList.get(0); fail("IndexOutOfBoundsException expected"); } catch (IndexOutOfBoundsException success) { } }

If the test should pass on exception thrown, catch the exception within the test and place fail() if it is not thrown


public void exampleTest () throws SomeApplicationException { // do some test}

Use JUnit assert/fail methods for throwing ExceptionsDon't catch exceptions unless they are expected to be thrown


Beware of floating-point comparison errors

assertEquals ("The result is different from what is expected", result, expected);

assertEquals ("The result is different from what is expected", 0.05 + 0.05, 1/10.0);

assertEquals ("The result is definitely different from what is expected ", result, expected, delta);

assertEquals ("The result is definitely different from what is expected", 0.05 + 0.05, 1/10.0, 0.01);


Testing protected and private methods

Protected: Place the tests in the same package as the classes

under test.

Private: avoid use Java Reflection to call a private method


Organizing files in catalog

| +--src | | | +--com | | | +--xyz | | | +--SomeClass.java +--test | +--com | +--xyz | +--SomeClassTest.java

com.xyz.SomeClass

com.xyz.SomeClassTest

Task 1Task 1

Write tests for existing code of RomanNumber class

RomanNumberRomanNumber

class RomanNumber { // initialize with an Arabic year public RomanNumber(int number); // initialize with a Roman year public RomanNumber(String number); // return the Roman value public String toRoman(); // return the Arabic value public int toArabic(); // return a Collection of legal Roman symbols public static Collection getRomanSymbols();}

Task 2Task 2

Implement RomanNumber class using test-first approach.

Testing firstTesting first

TestCase: INPUT: 1, EXPECTED: "I"

Implementation:String toArabic(int num) { return "I";}


TestCase: INPUT: 2, EXPECTED: "II"

Implementation:String toArabic(int num) { if (num == 1) return "I"; else return "II";}


TestCase: INPUT: 3, EXPECTED: "III"

Implementation:String toArabic(int num) { if (num == 1) return "I"; else if (num == 2) return "II"; else return "III";}


TestCase: INPUT: 3, EXPECTED: "III"

Implementation:String toArabic(int num) { while (num-- > 0) result += "I"; return result;}

Refactoring


TestCase: INPUT: 4, EXPECTED: "IV"

Implementation:String toArabic(int num) { if (num < 4) while (num-- > 0) result += "I"; return result; } return "IV";}


TestCase: INPUT: 5, EXPECTED: "V"

Implementation:String toArabic(int num) { if (num < 4) while (num-- > 0) result += "I"; return result; } else if (num == 4) { return "IV"; } else { return "V"; }}


TestCase: INPUT: 6, EXPECTED: "VI"

Implementation:String toArabic(int num) { if (num < 4) while (num-- > 0) result += "I"; return result; } else if (num == 4) { return "IV"; } else if (num == 5) { return "V"; } else return "VI";}


TestCase: INPUT: 8, EXPECTED: "VIII"

Implementation:String toArabic(int num) { if (num < 4) while (num-- > 0) result += "I"; return result; } else if (num == 4) { return "IV"; } else { result = "V"; while (num-- > 5) result += "I"; return result; }}

Refactoring


TestCase: INPUT: 9, EXPECTED: "IX"

Implementation:String toArabic(int num) { // 1..4.. else if (num < 9) { result = "V"; while (num-- > 5) result += "I"; return result; } else { return "IX"; }}


TestCase: INPUT: 10, EXPECTED: "X"

Implementation:String toArabic(int num) { // 1..4.. else if (num < 9) { result = "V"; while (num-- > 5) result += "I"; return result; } else (num == 9) { return "X"; } else { return "IX";}


TestCase: INPUT: 1976, EXPECTED: "MCMLXXVI"

Implementation:private class ConvSymbols {int arabic, String roman}{{1,I}, {4,IV}, {5,V}, {9,IX}, {10,X}, {40,XL}, ...}

String toArabic(int num) { for (int i = 0; i < sizeof(symbols); i++) { Symbol sym = symbols[i]; while (num >= symbol.arabic) { num -= symbol.arabic; result += symbol.roman; } }}

Refactoring

BibliographyBibliography

1. JUnit, http://www.junit.org/

2. Test Infected – Programmers love writing tests, http://junit.sourceforge.net/doc/testinfected/testing.htm

3. JUnit Cook's Tour, http://junit.sourceforge.net/doc/cookstour/cookstour.htm

4. Unit-testing Tools, http://www.xprogramming.com/software.htm

Q&AQ&A

Unit Testing Bartosz Walter Software Engineering Lecture XXX.

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