Given the following fragment of code, how many tests are required for 100% decision coverage?

Question

if width > length
    then
    biggest_dimension = width
    if height > width
        then
        biggest_dimension = height
    end_if
else
    biggest_dimension = length
    if height > length
        then
        biggest_dimension = height
    end_if
end_if

Given the following fragment of code, how many tests are required for 100% decision coverage? According to my calculation the answer should be 6 as I am calcualting true and false for each if condition but the actual answer is 4. can someone tell me how it got as 4?

Answer 1

I hope this will help you understand why the answer is 4.

100% Decision coverage

The code traverses 4 paths/decisions for 100% Decision coverage.

This happens when the decision statements are nested. In this case

"height > width" with execute only if "width > length" is true.

"height > length" with execute only if "width > length" is false.

Hence the minimum number of test cases required to cover 100% decision testing is 4.

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Edit: As per Polina's request I'm adding explanation for 100% Statement Coverage.

For this same piece of code you can achieve 100% Statement Coverage with just 2 sets of inputs,

Case 1.

Height = 10
Width = 8
Length = 5

In this case,

• if width > length will be true. Hence next statement biggest_dimension = width will be executed.
• if height > width will also be true. Hence next statement biggest_dimension = height will be executed.

Case 2.

Height = 7
Width = 5
Length = 6

In this case,

• if width > length will be false. Hence next statement biggest_dimension = length will be executed.
• if height > length will be true. Hence next statement biggest_dimension = height will be executed.

So you need a minimum of 2 tests for 100% Statement Coverage.