Testing can reveal the presence
of bugs, but cannot prove their
absence

The more bugs enter a quality assurance or
test activity, the more bugs will escape from
that activity

1. invalid
float x.0 3.0 4 5
char 3i 4 5
maxint+1 2^32 1 2
negative -3 4 5
2. valid
triangle
a. plus over flow but correct 2^31 2^31 2^31
b. quan bu bu xiang deng 18 23 9
c. deng yao 13 13 25
d. deng bian 8 8 8
not triangle
equal 10 10 20
// not equal