Unit Testing with JUnit and Clover

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• Unit Testing with JUnit and Clover

Based on material from Daniel Amyot JUnit Web
site
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JUnit (http//www.junit.org)

• A unit test framework for Java
• Authors Erich Gamma, Kent Beck
• Part of XUnit family (HTTPUnit, Cactus), CppUnit
• Essential part of the eXtreme Programming
  methodology, but can be used independently
• Used for regression testing as well, but not for
  system testing
• Integrated to Eclipse, but can be used standalone

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eXtreme Programming (XP) and unit testing

• In XP, a test shall
• Be written first
• before any code
• Executed
• will likely fail!
• Then
• Implementation code should be written that would
  be the minimum code required to get the test to
  pass and no extra functionality.
• Once the code is written, re-execute the test and
  it should pass.
• When needed, refactor the code mercilessly.
• Improve performance, maintainability, readability

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Common XP day
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Some benefits of JUnit (and Test-Driven
Development)

• Testing is a Good Thing
• Immediate gratification with build iterations
• Start with The Simplest Thing That Could
  Possibly Work.
• Green bar addiction!
• Break the cycle of more pressure means fewer
  tests
• Whenever you are tempted to type something into a
  print statement or a debugger expression, write
  it as a test instead.
• Martin Fowler
• Reduce code captivity
• If others can test it, others can work on it.

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What is a JUnit test?

• A test script is just a collection of small
  Java methods.
• General idea is to create a few Java objects, do
  something interesting with them, and then
  determine if the objects have the correct
  properties.
• What is added? Assertions!
• A package of methods that checks various
  properties
• equality of variables
• identity of objects
• The assertions are used to determine the test
  case verdict.

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A JUnit test case

• / Test of copy method, class
  ProblemBase.Value /
• public void testCopy()
• System.out.println("testCopy")
• Value v1 new Value( )
• v1.setName( "X" )
• Value v2 v1.copy( )
• v1.setName( "Y" )
• String expected "X"
• String actual v2.getName( )
• Assert.assertEquals( expected, actual )

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A JUnit test case

• / Test of copy method, class
  ProblemBase.Value /
• public void testCopy()
• System.out.println("testCopy")
• Value v1 new Value( )
• v1.setName( "X" )
• Value v2 v1.copy( )
• v1.setName( "Y" )
• String expected "X"
• String actual v2.getName( )
• Assert.assertEquals( expected, actual )

Method signature no parameters
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A JUnit test case

• / Test of copy method, class
  ProblemBase.Value /
• public void testCopy()
• System.out.println("testCopy")
• Value v1 new Value( )
• v1.setName( "X" )
• Value v2 v1.copy( )
• v1.setName( "Y" )
• String expected "X"
• String actual v2.getName( )
• Assert.assertEquals( expected, actual )

Objective create a duplicate object, instead of
copying reference
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A JUnit test case

• / Test of copy method, class
  ProblemBase.Value /
• public void testCopy()
• System.out.println("testCopy")
• Value v1 new Value( )
• v1.setName( "X" )
• Value v2 v1.copy( )
• v1.setName( "Y" )
• String expected "X"
• String actual v2.getName( )
• Assert.assertEquals( expected, actual )

Check for a condition that should not be violated
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A JUnit test class

• import junit.framework.
• // Each test class must extend the Junit
• // TestCase class
• public class CopyTest extends TestCase
• // Must provide a constructor with String
• // argument
• public CopyTest(String name)
• super(name)
• // Insert your test cases here. setup(),
• // tearDown() and main() methods can also be
• // added.

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Assertions and verdicts

• Assertions are defined in the special JUnit class
  Assert
• If the assertions are true, the method continues
  executing.
• If any assertion is false, the method stops
  executing, and the result for the test case will
  be fail.
• If any other exception is thrown during the
  method, the result for the test case will be
  error.
• If no assertions were violated for the entire
  method, the test case will pass.
• The Assert class name is often not required
• assertEquals( expected, actual )

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Assertion methods

• Assertion methods can verify
• Objects are identical, or not identical
• Objects are null or non-null
• Equality of objects
• via or equals() depending on type
• Boolean conditions are true or false
• There is also an unconditional failure method.

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JUnit execution (with failures)
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JUnit execution (success!)
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JUnit plugin for Eclipse
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JUnit framework
TestResult
fTests
Your tests here.
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Some benefits of this framework

• No major difference between a test case and a
  test suite
• Both can be invoked using the run() method
• Test cases are often associated with methods, and
  test suites with classes
• Uses reflection to lean about classes and methods
• Test suite structure discovered at run time
• Test suites can invoke the test cases
  automatically
• Common setup and teardown (clean up) for all test
  cases in a test suite
• Default ones can be overriden
• Integrated to Uis, and wizard for test creations
• Simple, efficient, and automated!

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Java code coverage tool Clover

• Discovers sections of code that are not being
  adequately exercised by your (unit) tests.
• Supports method, statement, and branch coverage
• Reports its findings in multiple formats
• From project level down to individual lines of
  source code
• Historical charting of code coverage and other
  metrics
• Integrated to Eclipse and other IDEs
• http//www.thecortex.net/clover/index.html

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Clover plugin for Eclipse
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Clover coverage filters

• One can choose not to instrument certain types of
  blocks in the code (e.g. assertions and exception
  catching), in order to focus on the coverage of
  interest.

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Clover plugin caveats

• This plugin may (very likely!) not work correctly
  if you have configured your Eclipse project so
  that the Java source and output directories are
  the same.
• Use different directories for the original source
  code and instrumented source code
• When compiling your Java project with the Clover
  plugin, you must add and use a Java Development
  Kit (JDK) to your list of Installed JRE locations
  (see instructions).
• Not free software

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Fixing the Clover plugin caveats
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For more information

• JUnit Web site
• http//junit.org
• Documentation on installation and use of JUnit
• E. Gamma, K. Beck, JUnit Cookbook
• http//junit.sourceforge.net/doc/cookbook/cookbook
  .htm
• Internals of JUnit
• JUnit A Cooks Tour
• http//junit.sourceforge.net/doc/cookstour/cooksto
  ur.htm
• Clover Eclipse Plugin (with installation
  instructions)
• http//www.thecortex.net/clover/userguide/eclipse/