Testing and debugging what slips through General Developer Topics Question

look at the following code (VB.NET)

Code:

        Dim VarKey1 As Byte
        Dim VarKey2 As Byte
        Dim VarKey3 As Byte

        'Generate new random keys
        Randomize()
        VarKey1 = CByte(255 * Rnd() + 1)
        VarKey2 = CByte(255 * Rnd() + 1)
        VarKey3 = CByte(255 * Rnd() + 1)

There is one helava big bug in that code .... and it has the probability of 1:85 in happening ....

In development and testing we executed the complete function about 1000 times already...

Today we were doing a quick speed test, just to see what sort of execution times the code has.. We recursivly called the function 1000 times,and on the 50th execution we hit a problem... "Overflow Error" ....
Look at the code again ... do you see it ???? ....

255 + 1 = 256 = More than a byte,the right code is: 254 * Rnd() + 1 ...

funny thing is this error did not occur on any of the 1000 previous executions, but as soon as we pushed it a little the crack opened up ...

Some bug's need you to push the code HARD to find them ...

Gremmy...