Invalid Data

Invalid data refers to any input that does not conform to the expected format, type, range, or rules defined in the software requirements or specifications. Invalid data is deliberately used in testing to evaluate the system’s ability to handle errors, exceptions, and unexpected input scenarios gracefully and securely.

Testing with invalid data helps identify weaknesses in a system’s validation mechanisms, error handling, and robustness. It ensures that the application behaves predictably and securely when faced with improper or malicious input, preventing crashes, data corruption, or vulnerabilities.

Types of Invalid Data:

1. Incorrect Format: Inputs that deviate from the expected format, such as entering letters where numbers are required or using an invalid date format (e.g., “abcd” in a numeric field or “31/02/2023” as a date).
2. Out-of-Range Values: Inputs outside the permissible range, such as a negative number where only positive values are allowed or an excessively large value that exceeds the field’s capacity.
3. Empty or Null Values: Missing inputs or explicitly null values in required fields, such as submitting a form without filling in mandatory fields.
4. Special Characters and Escape Sequences: Inputs containing characters that may disrupt normal processing, such as <script> tags in text fields or SQL injection payloads.
5. Boundary Violations: Data that tests the system’s limits, such as entering more characters than allowed in a field or exceeding file upload size limits.
6. Invalid Combinations: Inputs that are valid individually but invalid when combined, such as selecting incompatible options in a form.