.. Continuing the Beginners Guide to Software Testing series

The following basic techniques are employed during black box testing:

  • Equivalence Class
  • Boundary Value Analysis
  • Error Guessing

Equivalence Class:

  • For each piece of the specification, generate one or more equivalence Class
  • Label the classes as “Valid” or “Invalid”
  • Generate one test case for each Invalid Equivalence class
  • Generate a test case that covers as many Valid Equivalence Classes as possible

Equivalence Class

An input condition for Equivalence Class:

  • A specific numeric value
  • A range of values
  • A set of related values
  • A Boolean condition


Equivalence classes can be defined using the following guidelines:

  • If an input condition specifies a range, one valid and two invalid equivalence class are defined.
  • If an input condition requires a specific value, one valid and two invalid equivalence classes are defined.
  • If an input condition specifies a member of a set, one valid and one invalid equivalence classes are defined.
  • If an input condition is Boolean, one valid and one invalid classes are defined.

Boundary Value Analysis

  • Generate test cases for the boundary values.
  • Minimum Value, Minimum Value + 1, Minimum Value -1
  • Maximum Value, Maximum Value + 1, Maximum Value – 1

Error Guessing.

  • Generating test cases against to the specification.

Go back to Test Design Techniques

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