//Test Cases

Id accountId = '0016F00002AHDKV';
String accountIdInString = '0016F00002AHDKV';

//Case 1 : Pass Id value to String parameter
System.debug(IdMapExample.getDataUsingKeyWithString(accountId));
//Result : It will work properly and return a value as passed 15 digit Id value will be converted to 18 digit format.

//Case 2 : Pass String value to String parameter
System.debug(IdMapExample.getDataUsingKeyWithString(accountIdInString));
//Result : It will remain in 15 digit format but map we have created will have keys in 18 digit format and this case will fail
//         and will return null

//Case 3: Pass Id value to Id parameter
System.debug(IdMapExample.getDataUsingKeyWithId(accountId));
//Result: This will work as expected, passed 15 digit Id value will be converted to 18 digit format.

//Case 4: Pass String value to Id parameter
System.debug(IdMapExample.getDataUsingKeyWithId(accountIdInString));
//Result: This will work as well, passed 15 digit String value will be converted to 18 digit format.