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.

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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

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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
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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

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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

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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

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Pressman p 639

• Alpha testing
• Beta testing
• Recovery testing
• security testing
• Stress testing
• Performance tesing