Java Unit Test and Coverage Introduction

Java Unit Test and Coverage Introduction
Alex Su
2010/07/21

Copyright 2010 TCloud Computing Inc.

Agenda

•Test-driven development
•Junit
•Ant Integration
•Mock Object
• Mockito
•Code Coverage Analysis
•Coverage Tool
• Emma
• Cobertura
•Case Study

Trend Micro Confidential

Test-driven development

Test-driven development (TDD) is a software development
technique that relies on the repetition of a very short
development cycle

•Add a test
•Run all tests and see if the new one fails
•Write some code
•Run the automated tests and see them succeed
•Refactor code


Test-driven development - Scenario

Given/When/Then

Example 1: New lists are empty
Given a new list
Then the list should be empty.

Example 2: Lists with things in them are not empty.
Given a new list
When we add an object
Then the list should not be empty.


Test-driven development - Scenario
class ListTest {
@Test
public void shouldKnowWhetherItIsEmpty() {
List<String> list1 = new ArrayList<String>();
assertTrue(list1.isEmpty());

List<String> list2 = new ArrayList<String>();
list2.add("element");
assertFalse(list2.isEmpty());
}
}


Test-driven development


JUnit

• JUnit is a unit testing framework for the Java programming
language.

• JUnit is linked as a JAR at compile-time; the framework
resides under packages junit.framework for JUnit 3.8 and
earlier and under org.junit for JUnit 4 and later.


JUnit
• Test Runner
A Runner runs tests. You will need to subclass Runner when using
RunWith to invoke a custom runner.

• Test Fixture
A test fixture represents the preparation needed to perform one or more
tests

• Test Case
A test case defines the fixture to run multiple tests.

• Test Suite
A Test Suite is a Composite of Tests. It runs a collection of test cases.


Junit – Test Result

• Success

• Failure
A failure is when one of your assertions fails, and your JUnit
test notices and reports the fact.

• Error
An error is when some other Exception occurs--one you
haven't tested for and didn't expect, such as a
NullPointerException or an
ArrayIndexOutOfBoundsException.


Junit – Annotation

• @BeforeClass
• @AfterClass
• @Before
• @After
• @Test
• @Ignore


JUnit
public class DummyTest {
private static List<String> list;

@BeforeClass public static void beforeClass() {
list = new ArrayList<String>();
}
@AfterClass public static void afterClass() {
list = null;
}
@Before public void before() {
list.add("Alex");
}
@After public void after() {
list.remove("Alex");
}
@Test public void getElement() {
String element = list.get(0);
assertEquals(element, "Alex");
}
@Ignore("Not Ready to Run") @Test public void notRun() {
assertEquals(list.size(), 2);
}
@Test(expected = IndexOutOfBoundsException.class)
public void getElementWithException() {
list.get(1);
}
}


JUnit

@RunWith(Suite.class)
@SuiteClasses({
DummyTest1.class, DummyTest2.class})
public class DummyTestSuite {
}


JUnit
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations =
{ "classpath:appContext.xml" })
public class DummyTest {
@Resource
private DummyService dummyService;

@Test
public void createDummy() {
Dummy dummy = new Dummy();
dummy.setId(ID);
dummy.setName("Hermione Granger");
dummy.setDescription("Gryffindor");

dummyService.createDummy(dummy);

dummy = dummyService.getDummy(ID);
assertNotNull(dummy);
}
}


Junit – Ant Integration
<junit showoutput="${build.test.dir}" printsummary="on"
fork="yes" haltonfailure="false>
<classpath refid="classpath" />
<formatter type="xml" />

<batchtest todir="${build.test.dir}">
<fileset dir="${test.dir}">
<include name="**/*Test.java" />
</fileset>
</batchtest>
</junit>

<junitreport todir="${doc.test.dir}">
<fileset dir="${build.test.dir}">
<include name="**/TEST-*.xml" />
</fileset>
<report format="frames" todir="${doc.test.dir}" />
</junitreport>


Mock Object

•supplies non-deterministic results (e.g. the current
time or the current temperature);
•has states that are difficult to create or reproduce
(e.g. a network error);
•is slow (e.g. a complete database, which would
have to be initialized before the test);
•does not yet exist or may change behavior;
•would have to include information and methods
exclusively for testing purposes (and not for its
actual task).


Mock Object - Mockito

•Argument matchers
•Verifying exact number of invocations / at least x /
never
•Verification in order
•Shorthand for mocks creation - @Mock annotation
•Stubbing consecutive calls
•Spying on real objects
•Aliases for behavior driven development


Mock Object - Mockito
public class ListTest {
private List<String> mockedList;

@Before
public void initMocks() {
mockedList = mock(List.class);

given(mockedList.get(0)).willReturn("first", "second");
given(mockedList.get(1)).willThrow(new
IndexOutOfBoundsException());
}

@Test
public void getList() {
assertEquals("first", mockedList.get(0));
assertEquals("second", mockedList.get(0));
}

@Test(expected = IndexOutOfBoundsException.class)
public void getListWithException() {
mockedList.get(1);
}
}


Code Coverage Analysis

•Finding areas of a program not exercised by a set
of test cases.
•Creating additional test cases to increase coverage.
•Determining a quantitative measure of code
coverage, which is an indirect measure of quality.
•Identifying redundant test cases that do not
increase coverage.



•Basic Metrics
•Statement Coverage(Line)
•Basic Block Coverage
•Decision Coverage(Branch)
•Condition Coverage
•Multiple Condition Coverage
•Condition/Decision Coverage
•Modified Condition/Decision Coverage
•Path Coverage



•Statement Coverage(Line)
•Basic Block Coverage
•Decision Coverage(Branch)
•Condition Coverage
•Multiple Condition Coverage

boolean a = true, b = true;
if(a && b) {
System.out.println("true");
} else {
System.out.println("false");
}



•Condition/Decision Coverage(C/DC)
•Modified Condition/Decision Coverage(MC/DC)

boolean a = true, b = true;
if(a && b) {
} else {
}

if(a || b) {
} else {
}



•Path Coverage

Y
A = 3 and X = 5 A>1
A = 0 and X = 3

A = 0 and X = 0 N X=0
A = 2 and X = 0

A=2 Y
or
X>1

N X = 20

print x



•Other Metrics
•Function Coverage
•Data Flow Coverage
•Loop Coverage
•Race Coverage
•Relational Operator Coverage


Coverage Tool

•Instrumentation
• Source code instrumentation
• Bytecode instrumentation
• Runtime instrumentation


Coverage Tool

Possible feature Runtime Bytecode Source code

Gathers method coverage yes yes yes

Gathers statement coverage line only yes yes

Gathers branch coverage indirectly yes yes
Can work without source yes yes no
Requires separate build no no yes

Requires specialised runtime yes not accurate no

View coverage data inline
not accurate yes yes
with source

Source level directives to
no no yes
control coverage gathering

Runtime performace high impact variable variable
Container friendly no not accurate yes


Coverage Tool

•Reports are filterable so you can tell what needs to
be evaluated for code coverage.
•offline and on-the-fly instrumentation.
•Ant integration.
•JUnit integration.


Coverage Tool - Emma

•Last update : 2005-06-13
•Stats on both class and method coverage
•Partial/fractional line coverages is unique trait -
shown in yellow when there are multiple
conditions in a conditional block
•Stricter code coverage.
•Integration with Eclipse available -
http://www.eclemma.org/
•Better documentation than cobertura.
•Instrumentation process is faster than cobertura.
•Standalone library and does not have any external
dependencies.
•Common public license 1.0 friendlier that GPL.

Coverage Tool - Cobertura

• Last update : 2010-03-03
• GPL'd version of JCoverage (which is commercial).
• Prettier reports.
• Branch/block and line coverages only - no class or
method level coverage.
• How many times a line has been executed
• <cobertura-check> where one can specify percentage
of coverage that's a MUST or else build fails.
• Data merge feature - good for QA labs... for merging
coverage data to prepare historical trend graphs.
• Depends on other third party libraries.
• Integration with Eclipse available -
http://ecobertura.johoop.de/


Coverage Tool – Comparsion(Exception)

• Source Code
String str = "abc";
System.out.println(str.substring(5));

•Decompile Result
String str = "abc";


Coverage Tool - Comparsion(Exception)

• Emma
boolean aflag[] = ($VRc != null ? $VRc : $VRi())[3];
String s = "abc";
System.out.println(s.substring(5));
aflag[0] = true;



• Cobertura
boolean flag = false;
int __cobertura__branch__number__ = -1;
TouchCollector.touch("tcloud.dummy.service.CoverageTestMain", 25);
String str = "abc";



• Clover
__CLR3_0_217a17agbtkjkdv.R.inc(1571);
String str = "abc";


Coverage Tool – Comparsion(Loop)

•Source Code
List<String> list = new ArrayList<String>();
for(String element : list) {
System.out.println(element);
}

• Decompile result
String element;
for(Iterator iterator = list.iterator(); iterator.hasNext(); System.out.println(element))
element = (String)iterator.next();


Coverage Tool - Comparsion(Loop)

• Emma
boolean aflag[] = ($VRc != null ? $VRc : $VRi())[4];
List list = new ArrayList();
Iterator iterator = list.iterator();
aflag[0] = true;
do
{
aflag[2] = true;
if(iterator.hasNext())
{
String s = (String)iterator.next();
System.out.println(s);
aflag[1] = true;
} else
{
break;
}
} while(true);
aflag[3] = true;



• Cobertura
boolean flag = false;
int __cobertura__branch__number__ = -1;
Iterator iterator = list.iterator();
do
{
__cobertura__line__number__ = 37;
__cobertura__branch__number__ = 0;
{
if(__cobertura__branch__number__ >= 0)
{

TouchCollector.touchJump("tcloud.dummy.service.CoverageTestMain", __cobertura__line__number__, __cobertura__branch__numb
er__, false);
__cobertura__branch__number__ = -1;
}
String element = (String)iterator.next();
} else
{
if(__cobertura__line__number__ == 37 && __cobertura__branch__number__ == 0)
{

TouchCollector.touchJump("tcloud.dummy.service.CoverageTestMain", __cobertura__line__number__, __cobertura__branch__numb
er__, true);
__cobertura__branch__number__ = -1;
}
return;
}
} while(true); Trend Micro Confidential


• Clover
__CLR3_0_2145145gbu63tpg.R.inc(1462);
__CLR3_0_2145145gbu63tpg.R.inc(1463);
__CLR3_0_2145145gbu63tpg.R.inc(1464);
String element;
for(Iterator iterator = list.iterator(); iterator.hasNext();
System.out.println(element))
{
element = (String)iterator.next();
__CLR3_0_2145145gbu63tpg.R.inc(1465);
}



• Clover with decompile result
Iterator iterator;
__CLR3_0_2166166gbu71moi.R.inc(1535);
__CLR3_0_2166166gbu71moi.R.inc(1536);
__CLR3_0_2166166gbu71moi.R.inc(1537);
__CLR3_0_2166166gbu71moi.R.inc(1538);
iterator = list.iterator();
_L4:
{
__CLR3_0_2166166gbu71moi.R.iget(1539);
} else
{
__CLR3_0_2166166gbu71moi.R.iget(1540);
return;
}
if(true) goto _L2; else goto _L1
_L1:
break; /* Loop/switch isn't completed */
_L2:
__CLR3_0_2166166gbu71moi.R.inc(1541);
String element = (String)iterator.next();
if(true) goto _L4; else goto _L3
_L3:

Case Study


THANK YOU!


Java Unit Test and Coverage Introduction

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