error，fault, failure

1, findLast()

(1) The fault is that the state of the loop should be:

 

for(int i = x.length-1;i >= 0;i--)

Because if the expected index is in x[0], when i=0 the loop will not be execute because it doesn’t fit the state that I > 0.

(2) We must make sure it will not execute the i>0, so let x be null,

Test case: x=null y=2

Expected: NullPointerException

Actual: NullPointerException

 

(3) execute the fault but not cause error:

Test case: x = [1,2,5] y = 2

Expected: 1

     Actual: 1

(4) result error but not a failure:

Test case: x = [1,2,3] y = 5

Expected: -1

Actual: -1

To cause the error, we should let it execute the state i = 0, but I = 0 will cause the return -1, because it will be push out of the loop, at the same time ,there is no expected number in the array, so the actual result also is -1.

2,lastZero()

 

(1) The question says that finding the last zero, so we should start with the last index in the array, so for(int i = x.length – 1;i>=0;i--)

(2) Whatever the case is ,the int i=0 will be execute at first.

(3) Test case: x = [2,1,4]

Expected: i = -1

Actual: i = -1

(4)Test case: x = [0,1,2]

Expected: i = 0

Actual: I = 0