Blue

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Blues Support for Object-Oriented Testing

• By
• James Majidian
• Christopher Nersisyan

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Agenda

• Abstract
• Introduction
• Reason for this article
• Object Oriented Testing
• Blue Environment Testing
• Conclusion
• Personal Thoughts
• Questions?

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Abstract

• Reasons for Object-Oriented testing
• Object-Oriented programming is commonly used for
  large scale projects.
• Much research has been done on design and
  implementation, but minimal research on testing.
• By taking an object-oriented approach to testing,
  this presentation will show that with appropriate
  tools the cost of testing will not be greatly
  increased.

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Introduction

• Reasons for Object-Oriented Large Scale Systems
• Excellent structuring mechanism
• Units may be implemented separately.
• Implementation hiding
• Internal structure of data may be hidden, and
  changes will not affect users of the class,
  simplifying maintenance.
• Software reuse
• Reduction in the amount of software written
  improves reliability of system since tested
  classes may be reused.

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Introduction (Contd)

• Difficulties of Object-Oriented Testing
• Advantages of Object-Oriented Programming become
  disadvantages
• Advantages
• Excellent structuring mechanism.
• Implementation Hiding.
• Disadvantages
• Large number of individual units must be tested
• State of internal data not accessible via
  interfaces
• Individual test cases must be developed for all
  units
• Test cases must call each method supported by the
  class, prompt user for parameters and display
  results of method.
• Various combinations of these method calls must
  be exercised.
• Resulting test program may be more complex and
  larger than the class being tested

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Introduction (Contd)

• Solutions for Object-Oriented Testing
• Debug print statements
• Advantages
• Prints out relevant internal data.
• Disadvantages
• Could introduce new errors.
• Large volume of output may become difficult to
  interpret.
• Symbolic debugger
• Advantages
• Insert break points and examine data.
• Disadvantages
• Adds complexity.
• May not be able to display complex link
  structures.
• Blue

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Introduction (Contd)

• What is Blue?
• Specifically designed for testing object-oriented
  applications.
• Graphical environment which supports interactive
  creation of instances of classes and interactive
  invocation of their methods.
• Ability to examine the internal state variables
  of objects.
• Allows the programmer to interactively test their
  classes without writing a single line of test
  code.
• Both an object-oriented programming language and
  development environment.

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Reason for this article

• Object Oriented programming is common method of
  programming, but limited information exists on
  testing it.
• We felt that it would be beneficial to all to
  examine one method of Object Oriented testing,
  the Blue environment.

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Object Oriented Testing

• Procedure to test a class
• Create an instance of the class
• Call of method of the object
• Examine the internal data of object
• This can be achieved by the inclusion of
  appropriate mechanisms in the program development
  environment.

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Object Oriented Testing (contd)

• Environment Mechanisms
• Mechanism 1
• Interactively create an object of any class.
• Pass parameters to object.
• Once created, interactively invoke methods.
• Results are displayed.
• Mechanism 2
• Environment provides an inspection facility
  allowing internal data to be examined.
• Results are displayed
• Characteristic of Environment
• To support passing of objects, mechanisms must
  allow an arbitrary number of objects of arbitrary
  classes to be constructed.

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Blue Environment Testing

• Project Editor
• The empty area at the bottom of the main window
  is the object bench.
• Once a class within a project has been compiled,
  objects of that class may be created.
• Interactive creation of objects is achieved by
  selecting the class and clicking the Create
  button.
• An instance is interactively created and
  available for operation.
• Invoking the creation operation on a class
  results in a normal object creation, including
  the execution of the creation routine (the
  constructor in C/Java terminology).

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Blue Environment Testing (contd)

• Object Creation Dialogue
• Appears after create operation is invoked
• Allows user to enter routine parameters.
• At the top of this dialogue, the interface of the
  creation routine is displayed, with its header
  and comment.
• Further down is a text field for entering
  parameter values.
• Under the parameters is another field to provide
  a name for the object to be created.
• The large empty area in the middle of the
  dialogue provides a list of previously used
  parameters. It is provided for convenience during
  testing of a class.
• Previously made calls can be easily repeated by
  selecting a parameter combination from the list.

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Blue Environment Testing (contd)

• An object on the Object Bench
• Once the OK button is clicked in the dialogue the
  object is created and displayed on the object
  bench.
• The object is then available to the user for
  direct interaction.

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Blue Environment Testing (contd)

• Calling a routine on an object
• Clicking on the object with the right mouse
  button displays a menu that includes all
  interface routines of that object.
• Also included in the menu are two special
  operations available for all objects inspect and
  remove.

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Blue Environment Testing (contd)

• Symbols in the routine menu indicate whether a
  routine has parameters or return values.
• If the routine has parameters, a parameter
  dialogue similar to the one seen at the creation
  of the object is displayed
• On the click of the OK button the routine is
  executed and, if the routine returns results, the
  result values are displayed in another dialogue.

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Blue Environment Testing (contd)

• How interactive creation helps
• There is no need to complete all classes in a
  project before the first tests can be performed.
• Each class can be tested as soon as some of its
  routines have been completed.
• No need to write special purpose test code.

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Blue Environment Testing (contd)

• Composition
• During the interactive testing of the system,
  objects accessible on the object bench may be
  composed.
• i.e. one object may be passed as a parameter to
  the routine of another object.

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Blue Environment Testing (contd)

• Inspection of Objects
• Inspect operation
• Allows viewing of instance data of objects that
  dont provide accessor functions.
• Results are displayed graphically.
• Get places object on object bench to be examined
  later.
• Inspect opens another dialogue for Instance
  variable inspection.
• Inspections allow users to observe the effect of
  routine execution of internal data.

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Blue Environment Testing (contd)

• Record Facility
• Textually records all interactive object
  creations, method invocations, return values,
  text input and text output.
• This helps with test documentation.

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Blue Environment Testing (contd)

• Pedagogical Benefits
• Blue environment was initially developed as a
  teaching environment for first year students.
• Benefits as a teaching aid
• Incremental development
• No need to syntactically complete a whole
  application
• As soon as one class or routine is completed it
  can be compiled, and objects can be created,
  executed, and tested.
• Leads to greater motivation and earlier error
  detection (which is also beneficial for
  professional development).
• Class/object distinction.
• Allowing the direct creation of and interaction
  with objects greatly facilitates understanding.
• If a student has a class Person and creates
  three different people with different names, the
  role of the class and the role of each object
  becomes much more directly understandable.
• Programming without I/O
• Allows a clearer understanding of the abstraction
  concepts if routine calls are taught before
  language exceptions
• Interface/implementation distinction
• Testing support
• As was the goal of Blue, good testing is
  supported much better than in conventional
  systems.

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Blue Environment Testing (contd)

• Implementation
• A shell Blue class will be created and its
  constructor will hold the interactive call.
• When the shell class is compiled and executed,
  the interactive calls will be performed.
• This shell class will store the interval objects
  values and this data will be shown in the result
  dialogue box.

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Blue Environment Testing (contd)

• Interactive call under testing.

• Blue Shell Source Code

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Conclusion

• Object Oriented programming has great advantages
  to software development, but creates difficulties
  in testing.
• Blue has been designed to aid in testing Object
  Oriented programs, by reducing special purpose
  test code.
• Blue supports incremental testing to occur early
  in the project, aiding the stability of the
  application.
• Blue was created to aid teaching languages, and
  should be available online today.

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Personal Thoughts

• Its simplicity seems more detrimental than
  beneficial.
• Blue may be an effective tool for simple unit
  testing, but seems too elementary for industry
  use.
• First year students taught in the Blue
  environment may have trouble transitioning to
  actual programming environments.

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Any Questions?