Debugging and testing
Test the boundary around a validation rule
By SI100x · Published
Validation often fails at the edges rather than on an obviously invalid example. A boundary exercise helps you state what the rule actually allows, including values that are easy to confuse.
Try this exercise
- Choose one rule, such as a maximum message length. Write examples just below the limit, exactly at it and just above it.
- Try empty input, whitespace-only input and an unexpected type where the interface allows it. Keep the expected behavior explicit for each case.
- Check the visible error and whether the rejected value was saved. Test a valid value afterward so failure handling does not leave the form stuck.
Check your result
The client’s guidance and the server’s acceptance should agree. Do not assume that a disabled button protects an operation when the same request can reach the server by another route.
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