1. Short URL Generation

a. Correct short URL generation

Description: Check that a long URL is converted to a short URL.
Input: Valid long URL (e.g. http://example.com/very-long-url).
Expected result: A valid short URL (e.g. http://short.ly/abc123).

b. Unique short URL generation

Description: Make sure different long URLs create different short URLs.
Input: Several long URLs.
Expected result: Each long URL has a unique short URL.

c. Handling repeated URLs

Description: Make sure the same long URL returns the same short URL.
Input: Same long URL many times.
Expected result: Same short URL every time.

2. URL Expansion

a. Correct URL expansion

Description: Check that a short URL expands to the long URL.
Input: Valid short URL.
Expected result: Correct long URL.

b. Handling non-existing URLs

Description: Check when the short URL does not exist.
Input: Invalid short URL.
Expected result: Error message (e.g. “URL not found”).

3. URL Validation

a. Invalid long URL

Description: Check invalid long URLs.
Input: Bad long URL (e.g. htp://invalid-url).
Expected result: Error message.

4. Edge Cases

a. Very long URL

Description: Test a very long URL.
Input: More than 2000 characters.
Expected result: System handles it or returns error.

b. Empty URL

Description: Test an empty URL.
Input: “”.
Expected result: Error saying URL cannot be empty.

5. Redirection

a. Correct redirection

Description: Check that short URL redirects to long URL.
Input: Valid short URL.
Expected result: User goes to correct long URL.