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Testing fundamentals

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Testing fundamentals Objectives Testing is a process of executing a program with the intent of finding an error. A good test case is one that has a high probability ... – PowerPoint PPT presentation

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Title: Testing fundamentals


1
Testing fundamentals
  • Objectives
  • Testing is a process of executing a program with
    the intent of finding an error.
  • A good test case is one that has a high
    probability of finding an as yet undiscovered
    error
  • A successful test is one that uncovers an as yet
    undiscovered error
  • Note Testing cannot show an absence of defects,
    it can only show that software defects are
    present.

2
White Box Testing
  • White box testing is a test case design method
    that uses the control structure of the procedural
    design to derive test cases.
  • Will guarantee that all independent paths within
    a module have been exercised at least once,
  • Exercise all logical decisions on their true and
    false sides,
  • Execute all loops at their boundaries and within
    their operational bounds
  • And exercise internal data structures to ensure
    their valididty

3
Why spend time on details and not requirement
satisfaction
  • Logic errors and incorrect assumptions are
    inversely proportional to the probability that a
    program path will be executed.
  • Errors tend to creep into our work when we design
    and implement function, conditions or control
    that are out of the mainstream. Everyday
    processing tends to be well understood while
    special case processing tends to fall into the
    cracks
  • We often believe that a logical path is not
    likely to be executed when in fact, it may be
    executed on a regular basis. That is, our
    unconscious assumptions about flow of control and
    data may lead us to make design errors that are
    uncovered only once path testing begins
  • Typographical errors are random. When a program
    is translated into programming language source
    code, it is likely that some typing errors will
    occur. Many will be uncovered by syntax checking
    mechanisms but others will go undetected until
    testing begins. It is as likely that a type will
    exist on an obscure logical path as on a
    mainstream path

4
Example of cyclomatic complexity testing
1
1 do while records remain in file
read record 2 if record field 1 0 3
than process record store buffer counter 4
else if record field 20 5 than reset
counter 6 else process record store in
file 7a endif 7b enddo 8 end
2
4
6
3
5
7a
7b
8
5
Other types of white box testing
  • Condition testing
  • If else, Boolean
  • Loop testing
  • Simple loop
  • Skip the loop entirely
  • Only one pass through the loop
  • Two passes through the loop
  • M pass through the loop where mltn
  • N-1, n, n1 passes through the loop
  • Nested loop(if we attempt the simple loop
    infinite test)
  • Start at the innermost loop, set all loops to
    minimum values.
  • Conduct simple loop tests for the innermost loop
    while holding the outer loops at their minimum
    values
  • Work outwards, conducting test for the next
    loop.(values typical
  • Continue until all loops have been tested

6
Black box testing
  • Focus on the functional requirements of the
    software. The software engineer derives sets of
    input conditions that will fully exercise all
    functional requirements for a program.
  • Attempts to find
  • Incorrect or missing functions,
  • Interface errors
  • Errors in data structures or external database
    access
  • Performance errors
  • Initialization and termination errors
  • Unlike white box testing, which is performed
    early in the testing process, black bos testing
    tend to be applied during later stages of testing

7
Test are designed to answer the following
questions
  • How is functional validity tested
  • What classes of input will make good test cases
  • Is the system particularly sensitive to certain
    input values
  • How are the boundaries of data class isolated
  • what data rates and data volume can the system
    tolerate
  • What effect will specific combinations of data
    have on system operations

8
Black box test cases
  • Boundary value analysis
  • Cause effect (if event occurs what reaction
    expected)
  • Comparison testing (realtime nuclear, aircraft)
    dev by dif teams results compared

9
Pressman p 639
  • Alpha testing
  • Beta testing
  • Recovery testing
  • security testing
  • Stress testing
  • Performance tesing
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