Tell us about the test design technique known as 'Error Guessing'.

Error Guessing test design technique is based on the tester's intuition, experience, and knowledge about possible defects in software. The essence is to hypothesize where and what kind of errors might occur, and to create tests aimed directly at detecting these suspected defects.

Main aspects:

• Reliance on experience: The tester uses their previous experience with similar systems, knowledge of typical programming errors, vulnerabilities, and issues that arise under certain conditions.
• Knowledge of the application: A deep understanding of the functionality, architecture, and logic of the tested application allows predicting problematic areas.
• Requirements analysis: Studying documentation and requirements can reveal ambiguities, contradictions, or missed scenarios that may lead to errors.
• Typical testing areas:
  • Boundary conditions.
  • Handling incorrect, null, or empty input data.
  • Handling exceptions and errors.
  • Working with databases (constraints, data types, relationships).
  • Behavior under high load or resource shortages.
  • Working with sessions and authorization.
  • "Negative" paths (negative scenarios).

Examples of suspected errors:

• Buffer overflow when entering a long string.
• Division by zero.
• Incorrect handling of date and time.
• Problems with concurrent access to resources.
• Memory leaks.
• Incorrect handling of special characters.

This technique is effective for quickly identifying critical defects but heavily depends on the tester's qualification and experience. It is often used in combination with formal test design techniques to ensure more comprehensive coverage.