Test Case Design Techniques:

1. Equivalence Partitioning:
This technique divides the input data of a software application into partitions of equivalent data. Test cases are then designed to cover each partition with representative values. For instance, if an input field accepts numbers from 1 to 100, equivalence partitioning suggests selecting one valid input (e.g., 50) and one invalid input from each partition (e.g., 0, 101) to ensure comprehensive testing.

2. Boundary Value Analysis (BVA):
BVA complements Equivalence Partitioning by focusing on boundary values. Test cases are designed using the minimum, maximum, and just inside/outside boundaries of input ranges. This helps identify errors that are likely to occur at the edges of input domains. For example, if a field accepts values from 1 to 10, test cases would include inputs like 1, 10, 2, and 9.

3. Decision Table Testing:
Decision tables are used to test software behavior based on different combinations of input conditions. This technique is effective for testing complex business rules and logic-driven functionalities. Test cases are derived from all possible combinations of inputs and their corresponding actions or outcomes.

4. State Transition Testing:
State transition testing is particularly useful for systems with different states or modes. Test cases are designed to cover transitions between these states, ensuring that the software behaves as expected when moving from one state to another. This technique helps identify issues related to state transitions, such as incorrect sequencing or missing transitions.

5. Pairwise Testing (Combinatorial Testing):
Pairwise testing aims to reduce the number of test cases required for exhaustive testing by covering all possible pairs of input parameters. It is based on the observation that many faults are triggered by interactions between pairs of input values rather than individual values. Pairwise testing helps achieve a balance between test coverage and test efficiency.

6. Use Case Testing:
Use case testing involves designing test cases based on the functional requirements specified in use cases. Test cases are derived from scenarios outlined in use case diagrams, ensuring that the software meets user expectations and fulfills intended business processes.

These are some of the most prominent test case design techniques widely discussed and utilized in functional testing forums and communities. Each technique has its strengths and weaknesses, and the choice of technique depends on factors such as the nature of the software under test, available resources, and testing objectives.