Test cases for string inputs [closed]

Answer 1

ReDos vulnerabilities if a Regular Expression is used

http://msdn.microsoft.com/en-us/magazine/ff646973.aspx

Answer 2

• localization concerns regarding number formats (decimals / commas)
• behavior sensitivity of special characters (for example supporting single quotes, but still being capable of parsing a name like Jim O'malley)
• escape character, and ending a string with the escape character - for example if your escape character is ^, and the user inputs something like See above^
• new lines in a string intended as single-line.

the list is endless though because it really depends on how you intend to use the string, and where it came from.