Lecture 6 Software Testing and jUnit

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Lecture 6Software Testing and jUnit

• CS140
• Dick Steflik

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Definition

• Software testing can be stated as the process of
  validating and verifying that a computer
  program/application/product
• meets the requirements that guided its design and
  development,
• works as expected
• can be implemented with the same characteristics
• and satisfies the needs of stakeholders.

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Motivation

• a study by NIST in 2002 reports that software
  bugs cost the US economy 59.5 billion annually
• In a study by Cambridge UK , Judge Business
  School the global cost is 312 billion

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It is commonly believed that the earlier a defect
is found, the cheaper it is to fix it. The
following table shows the cost of fixing the
defect depending on the stage it was found.11
For example, if a problem in the requirements is
found only post-release, then it would cost
10100 times more to fix than if it had already
been found by the requirements review.
11. McConnell, Steve (2004). Code Complete (2nd
ed.). Microsoft Press. p. 29. ISBN 0-7356-1967-0.
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Testing Methods

• Static Testing
• reviews , walkthroughs, inspections
• Dynamic
• methodologies that actually use / run the code
• White Box Testing
• testing the internal structures of the software
  rather than the functionality exposed to the end
  user
• Black Box Testing
• tester has no knowledge of how the software works
  (black box) and only applies inputs and checks
  outputs
• Gray Box Testing
• involves having knowledge of internal data
  structures and algorithms for purposes of
  designing tests, while executing those tests at
  the user, or black-box level. The tester is not
  required to have full access to the software's
  source code

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Testing Levels

• Unit Testing
• component testing. In OO environments (C, Java,
  Eiffle) this usually the class level.
• Integration Testing
• Testing to verify the interfaces between
  components against a software design
• System Testing
• testing a completely integrated system to verify
  it meets its requirements
• Acceptance Testing
• Testing by the customer at delivery time.

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Unit Test

• Usually done by the developers while they are
  developing the software
• Can involve both static and dynamic methods
• By keeping automated testing code, programmers
  can verify that they haven't broken something
  along the way.
• Software to manage these tests are often called
  code-driven testing frameworks.

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xUnit

• Unit testing framework developed by Kent Beck for
  the Smalltalk language originally known as Sunit
  (1998)
• Ported to Java as JUnit and C and C as CppUnit

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xUnit Architecture

• All xUnit Frameworks share a commmon architecture
• Test Runner - is an executable program that runs
  tests implemented using an xUnit framework and
  reports the test results
• Test case - is the most elemental class. All unit
  tests are inherited from here
• Test fixture - the set of preconditions or state
  needed to run a test. The developer should set up
  a known good state before the tests, and return
  to the original state after the tests
• Test suites - a set of tests that all share the
  same fixture. The order of the tests shouldn't
  matter
• Test execution test setup , test run , test
  tear down
• Test formatter formats the test outputs into
  useable format
• Assertions - a function or macro that verifies
  the behavior (or the state) of the unit under
  test. Usually an assertion expresses a logical
  condition that is true for results expected in a
  correctly running system under test (SUT).
  Failure of an assertion typically throws an
  exception, aborting the execution of the current
  test.

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Sample Junit Fixture
import org.junit. public class TestFoobar
_at_BeforeClass public static void setUpClass()
throws Exception // Code executed before
the first test method _at_Before public void
setUp() throws Exception // Code executed
before each test _at_Test public void
testOneThing() // Code that tests one
thing _at_Test public void testAnotherThing()
// Code that tests another thing
_at_Test public void testSomethingElse()
// Code that tests something else _at_After
public void tearDown() throws Exception
// Code executed after each test _at_AfterClass
public static void tearDownClass() throws
Exception // Code executed after the last
test method
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References

• http//en.wikipedia.org/wiki/Software_testing
• http//en.wikipedia.org/wiki/Junit
• http//junit.org/
• http//www.tutorialspoint.com/junit/