Test Writing: Swap Section

Created By: Rohith Sanjay

/ Version: 2024.10.1

Write a method called swapSection that takes in 3 arguments in this order: an array of ints, a start index (int), and an end index (also an int). The problem "swaps" pairs of elements in a section of the array array, from the start index (inclusive) to the end index (also inclusive), and returns the swapped/modified array. If you need to swap an odd number of elements, do not change the last element (only swap the pairs before it). Here are some examples:

In the following examples, the swapped elements are in bold.

Example 1 (even length; entire array): Array: [1, 2, 3, 4, 5, 6], startIndex: 0, endIndex: 5. Your method should return the array [2, 1, 4, 3, 6, 5]. Note how each pair is being reversed/swapped (e.g. [1, 2] turns into [2, 1]).

Example 2 (odd length; entire array): Array: [1, 2, 3, 4, 5], startIndex: 0, endIndex: 4. Your method should return [2, 1, 4, 3, 5]. Note how the last element is not being swapped, because it's not part of a pair.

Example 3 (even length; sub-array): Array: [1, 2, 3, 4, 5, 6], startIndex: 1, endIndex: 4. Your method should return the array [1, 3, 2, 5, 4, 6]. In this case, only the sub-array (elements of index 1 through 4) are being swapped. Thus, we swap the pairs only in that sub-array, and keep the rest of the array the same.

Example 4 (odd length; sub-array): Array: [1, 2, 3, 4, 5, 6], startIndex: 1, endIndex: 3. Your method should return the array [1, 3, 2, 4, 5, 6]. Here, we are interested in indices 1, 2, and 3 (3 elements, an odd number), so we do NOT change the last of the 3 elements (only the first pair).

Special Cases:

1. The passed array can be null! In this case, just return the original array (which is null) with no changes. *
2. The start and end index can be invalid! Specifically, if the start index is higher than the end index, if the start/end indices are larger than the array's length, or if they are negative, then you should just return the original array with no changes.

Hints:

1. Declare a new array of the same size as the original array's length. Populate (fill up) this array one element at a time, and then return this array at the end.
2. When you're populating the array to be returned, you may have to set both element i and element i+1, because you're swapping one pair at a time.
3. Remember: the start and end indices are inclusive for your search bounds!

Test Design Challenge

You're challenge is to write tests for this problem described above.

• Provide a method named test that accepts no arguments and does not return a value.
• If the implementation of the class described above is incorrect, your test method should throw an exception.
• If it is correct, do not throw an exception.
• You may want to use Java's assert method