What is the recommended approach for testing all combinations of inputs and preconditions?

The recommended approach for testing all combinations of inputs and preconditions involves utilizing risk analysis and priorities to focus testing efforts. This is crucial because exhaustive testing, which aims to cover every possible combination of inputs and preconditions, can be impractical and often infeasible due to the sheer number of combinations that may exist in a complex system.

By applying risk analysis, testers can identify which combinations of inputs and preconditions are most likely to result in defects or failures, thereby allowing for more efficient use of resources and time. Prioritizing testing efforts based on risk helps ensure that the areas of the application that are most critical or most prone to errors are thoroughly tested, while also managing the scope to a more manageable level.

This approach aligns with common testing principles that emphasize the importance of risk management and efficient resource allocation in the testing process, rather than attempting an exhaustive test which is often neither practical nor cost-effective.