What test design techniques do you know and use?

Main test design techniques I use:

• Equivalence Partitioning — dividing input data into classes of equivalence to test one representative from each class.
• Boundary Value Analysis — testing values at the boundaries of ranges where errors often occur.
• Cause-Effect Graphing — constructing a graph to identify logical relationships between conditions and actions.
• Decision Tables — systematizing conditions and corresponding actions for complex logic.
• Use Case Testing — verifying functionality through real user scenarios.
• Exploratory Testing — dynamically exploring the application without pre-prepared test cases.

Example of usage:

For a form with an age field, I apply equivalence partitioning: age < 0 (incorrect), 0–120 (correct), >120 (incorrect). Then I check boundary values: 0, 1, 119, 120, 121.