Test one ?

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Test Case 1: Input Validation

Input: An empty string or a string containing only whitespace characters.

Expected Output: An error message indicating that the input is invalid.

Test Case 2: Correct Input

Input: "Hello, World!"

Expected Output: The output should be the same as the input: "Hello, World!"

Test Case 3: Input with Different Case

Input: "hElLo, wOrLd!"

Expected Output: The output should ignore case and be the same as the input: "hElLo, wOrLd!"

Test Case 4: Input with Non-Alphanumeric Characters

Input: "Hello, world!?!?!."

Expected Output: The output should remove all non-alphanumeric characters and be: "HelloWorld"

Test Case 5: Input with Special Characters

Input: "Hello, wöٍrld!"

Expected Output: The output should remove all special characters and be: "HelloWorld"

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