Question

Code Analysis (1)

public int countPositive(int[] x) {
//Effects: If x == null throw NullPointerException
//Else return the number of positive (non-zero) elements in x
int count = 0;
for (int i = 0; i < ; i++) {
if (x[i] >= 0) {
count++;
}
}
return count;
}
// Test Input: x = [-4, 2, 0, 2]
// Expected output = 2

If possible, identify a test case that executes the fault, but does not result in an error state

A.) Test input: x = [0, 0, 0]; Expected output = 0

B.) Test input: x = [-4, 1, 5]; Expected output = 2

C.) Test input: x = [0, 4, 7]; Expected output = 2

D.) No test case possible

Answer 1

The best test case that exposes the fault in the code without resulting in an incorrect output is option A, where the input array x = [0, 0, 0] leads to an expected output of 0. Despite the fault considering zeros as positive, the expected count of positive numbers remains accurate.

Step-by-step explanation:

The code is supposed to count the number of positive (non-zero) elements in an array, but there’s a fault: the if statement checks for x[i] >= 0, which incorrectly includes zero as a positive number. Thus, the correct behavior of the method should only consider numbers greater than zero as positive.

To identify a test case that exposes this fault without creating an error state (incorrect output), we must find a set of numbers where the inclusion of zero does not change the expected count of positive numbers. Looking at the options provided, the best fit for this requirement is:

Option A: Test input x = [0, 0, 0]; Expected output = 0. In this test case, even though the method incorrectly counts zero as positive, the expected result (counting the actual positives) is still zero – which is correct despite the fault in the code.