How do you implement exception handling in Robot Framework?

Robot Framework provides several ways to handle exceptions, allowing you to gracefully manage errors and prevent your tests from abruptly stopping. Here's a breakdown of the common techniques:

1. Run Keyword And Expect Error:

Purpose: This keyword is used to intentionally expect an error to occur. It's useful for testing error handling scenarios in your application.
How it works: You provide the keyword that you expect to raise an error and the expected error message (or a pattern to match the message). If the keyword raises the expected error, the test continues; otherwise, it fails.
Example :

***Test Cases***
Verify Invalid Login
    Run Keyword And Expect Error    Invalid username or password    Login User    invalid_user    wrong_password
    Log    Error message was expected

2. Run Keyword And Ignore Error:

Purpose: This keyword executes a keyword and ignores any errors that occur. The test will continue even if the keyword fails.
How it works: It runs the specified keyword, and if an error occurs, it's caught and logged, but the test execution continues. This can be useful for situations where you want to try an action but don't want the test to fail if it doesn't succeed (e.g., trying to close a window that might not be open).
Example :

***Test Cases***
Attempt to Close Window
    Run Keyword And Ignore Error    Close Window
    Log    Window closing attempted

3. TRY / EXCEPT Blocks:

Purpose: These blocks provide a more structured way to handle exceptions, similar to try-except blocks in Python.
How it works: You define a block of code within TRY, and if any keyword within that block raises an exception, the execution jumps to the corresponding EXCEPT block. You can have multiple EXCEPT blocks to handle different types of exceptions or error messages.
Example :

***Test Cases***
Handle Database Connection
    TRY
        Connect to Database
        Query Database
    EXCEPT    Database connection failed
        Log    Failed to connect to the database
    EXCEPT    Database query error
        Log    Error during database query
    ELSE
        Log    Database operations successful
    FINALLY
        Disconnect from Database  # Always disconnect, even if there were errors

4. Assertions:

Purpose: While not strictly exception handling, assertions are crucial for verifying expected outcomes and detecting errors. If an assertion fails, it raises an exception, which can then be handled using the techniques above.
Examples :

Should Be Equal    ${actual_value}    ${expected_value}
Element Should Be Visible    login_button

5. Fatal Error:

Purpose: This is a special type of exception that stops the entire test execution. It's used for critical errors that make it impossible to continue testing.
How it works: If a keyword raises a Fatal Error, Robot Framework will stop the test run immediately.
Example: (This is usually raised by libraries or custom keywords in critical situations).

from robot.api.exceptions import FatalError

def my_keyword():
    if some_critical_error:
        raise FatalError("Critical error occurred!")