CSC 213

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CSC 213 Large Scale Programming

• Lecture 5
• Testing jUnit

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Todays Goal

• Discuss automated method of testing code
• Java-based approach to define test cases
• Show how to run these test cases
• How often code should be tested
• Present methods of handling failed tests
• How to find the source of the bug
• What can be done to fix bugs once they occur

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Assertions

• Tests that a boolean property holds
• Can be placed anywhere in a method
• Will be tested each time method is executed
• Can slow down performance, since always tested
• But very useful while program is incomplete
• Assertions added or removed at runtime
• Runs will test assertions if run with ea
  argument
• Otherwise assertions will not be run
• But tracking bugs source can be difficult

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Automated Testing

• Automation important for several reasons
• Allows for testing as code is written
• Keeps code in working order as it is developed
• Prevent regression failures as project continues
• Using JUnit for unit testing
• Written in Java and incorporated into Eclipse
• Simplifies process of performing checks
• Working in Java enables writing precise
  detailed tests

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Format of JUnit Test Cases

• Define test class for each class tested
• Include one method for each test case
• Helpfully, JUnit runs all tests within a class
• Eclipse can execute all test classes in a project
• Requires Java annotations for this to work
• Annotations add information to individual methods
• Annotation immediately precede method
• No spaces, blank lines, ifs, ands, or buts
• Can be odd at first, but will adapt very quickly

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Running JUnit Tests

• Begins by executing _at_BeforeClass method
• Then for each method marked _at_Test
• Run all methods marked _at_Before
• Perform any setup you would like for your tests
• Execute the one _at_Test method
• Run all methods marked _at_After
• These close files other cleanup from _at_Before
• Finally executes _at_AfterClass method

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JUnit assert____ Methods

• Actual tests performed using these methods
• assertTrue(boolean test)
• assertFalse(boolean test)
• assertSame(Object expected, Object actual)
• assertNotSame(Object expected, Object actual)
• assertNull(Object object)
• assertNotNull(Object object)
• fail()

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Other Important Tests

• When working properly, tests defined first
• Tests had better fail until the code actually
  written
• But do not want to see these as failures, yet
• Tell JUnit to skip the test with _at_Ignore
  annotation
• Also test that methods fail correctly
• Must state thrown exception in _at_Test
  annotation_at_Test(expectedMyException.class)
• Only passes test if MyException exception thrown

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My Test Failed, Now What?

• Run your tests often
• If only 1 line changes, source of bug is on that
  line
• If 1000 lines change, bug is somewhere
• Keep test cases simple
• Limit number of causes for the failure
• Trace your code by hand to find error or
• Use System.err.println to follow values
• Double-check that preconditions are met
• If not, check methods for where preconditions fail

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Daily Activity

• Finish documenting methods in the Board class and
  start writing assertions unit tests

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For Next Lecture

• Discuss automated method of testing code
• Java-based approach to define test cases
• Provide simple approach to run test cases
• Discuss range of possible tests to perform
• How often code should be tested
• Begin discussing GUIs
• How to implement in Java
• What event-driven programming is