Developing an ObjectOriented Software Testing and Maintenance Environment

1
Developing an Object-Oriented Software Testing
and Maintenance Environment
2
Summary of Problems In OO Testing

• The Understanding Problem
• The Complex Independency Problem
• The Object state Behavior Problem
• The tool support Problem

3
The Understanding Problem

• Problem introduced by encapsulation and
  information-hiding features.
• This feature results in delocalized plan
• A delocalized plan have several member functions
  from possibly several object classes invoked to
  achieve an intended functionality.
• Let us show this by an example ? InterViews
  Library
• Rectangles ? Member functions
• Edges ? Function invocations from left to
  right

4

• Table summarizes the number of invocation chains
  of different lengths for InterViews library.

By a chain of member functions calling in
sequence we mean that the first function calls
the second, which calls the third and so
forth. Strategy The tester has to understand
the sequences of member functions and semantics
of the classes prior to preparing any test cases
or modifying the intended functionality.
5
The complex Dependency Problem

• Caused by complex relationships(
  inheritance,aggregation etc) that exist in an OO
  program.
• It is difficult to understand that a given class
  in a large OO program if that class depends upon
  many other classes.
• A tested may not know where to start testing an
  OO library.
• It is extremely costly to construct test-stubs
• It is impossible to predict and test all
  possible used of a template class.
• It is difficult to identify and test the effect
  of polymorphism and dynamic binding.
• It is difficult to identify the changes impact in
  OO maintenance since the impact may be ripple
  throughout the program.

6
The State Behavior Testing Program

• Effect of an operation on an object depends upon
  the state of object and may change the state of
  an object.
• Let us try to understand this problem with an
  example of a coin box of a vending machine
  implemented in C.
• It accepts only quarters and allows vending when
  two quarters are received.
• It keeps track of total quarters received,
  current quarters received and whether vending
  machine is enabled or not.
• Functions mainly consists of
• Adding a quarter
• Returning the current quarters
• Resetting the coin box to initial state
• Vending

7
(No Transcript)
8

• Check the errors in the code? If a customer
  requests that two quarters be returned after
  inserting two quarters , he gets a free drink.
• This error is only located if we apply object
  state behavior testing method.
• Approach
• From the source code , we derive the
  state-dependent behavior of the objects.
• Represent this information on OSD, object state
  diagram.
• Generate the test cases and test data from OSD
• Observe the output

9
The Tool Support Problem

• CASE tools to support OO testing and maintenance
  are still using conventional testing and
  maintenance methods.
• Tool support is crucial in the maintenance phase.
• OO testing is tedious process. Ripple effects are
  common in OO programming.
• Identification of changes and impact of changes
• Generation and / or reuse of test cases and test
  data sets
• Retesting only the parts that are changed and/ or
  affected.

10
Results of Efforts to Solve The Problems

• An OO test model and Reverse Engineering approach
  to recover the designs of C programs
• A three level schema and algorithm for data flow
  testing of OO programs
• Definition and identification of class firewalls
  and test strategy for regression testing of C
  programs
• A program based method for object state behavior
  testing
• A scenario based method for integration and
  acceptance testing
• Part of these Results are implemented in an
  integrated object-oriented testing and
  maintenance (OOTM) environment

11
OOTM

• Three Diagrams are extracted from code using
  reverse engineering approach.
• Object Relation Diagram ( ORD )
• Block Branch Diagram ( BBD )
• Object State Diagram (OSD )
• An ORD represents the inheritance, aggregation,
  association, instantiations, uses, and nested
  relationships.
• A BBD represents the control structure of a
  member functions so that tester know which data
  is used and or updated. It can be used to prepare
  functional test cases, structural test cases, and
  test harness in member functions.

12

• An OSD is like a state chart and represents the
  state behavior of the objects. To reduce
  complexity , we construct the a state machine for
  each state-dependent data member of a class. The
  state behavior of a class is represented by the
  aggregation of the data members state machines.

13
Fig ORD for a subset of InterViews Library
14
Fig Class firewall for subset of Interviews
Library
15
Use of Firewall tool

• Before making actual changes, a developer can use
  the tool to identify the impact of the planned
  changes and estimate the efforts in terms of
  number of test stubs and test cases needed to
  retest the affected classes.
• After making the changes, a regression tester can
  use the tool to identify the actual changes and
  their impact. The tool can also compute the
  optimal test order to retest the affected classes

16
A nonflat state machine for the incorrect coin
Box class
17
Test Tree showing the execution sequence of a
COSD.
18
Usefulness of OO Test Model

• It helps the tester and maintainer understand the
  structure of and relations between the components
  of an OO program.
• It provides the tester and maintainer a
  systematic method to perform OOTM.
• It facilitates the definition and analysis of OO
  testing criteria.
• It facilitates the development of various
  algorithm and capabilities for OOTM