 <p>There is difference between 1 and 0.1: your first case shows whole number while second case shows fractional.</p> <p>So if you test 10-20 range with value of 9.9 you may get error of data type (fractional instead of whole, or float instead of byte). By doing that, instead of testing range you test data type. This test is also important but different from the boundary analysis.</p>