In cases where the user can predict when an error might occur in the application, they can check for that error and explicitly raise an exception if it is found. Take the login function of a browser or mobile application as an example. If the user credentials are incorrect, the app will throw an exception saying something like "username invalid, try again" or "password incorrect, please re-enter".

The exception can be explicitly handled in a way that the actual error message can be thrown in the exception. Here is an example of the login method we wrote earlier with exception handling added to it:

@FindBy(id="myApp_exception")
protected M error;

/**
 * login - method to login to app with error handling
 *
 * @param username
 * @param password
 * @throws Exception
 */
public void login(String username,
                  String password)
                  throws Exception {

    if ( !this.username.getAttribute("value").equals("") ) {
        this.username.clear();
    }

    this.username.sendKeys(username);

    if ( !this.password.getAttribute( "value" ).equals( "" ) ) {
        this.password.clear();
    }

    this.password.sendKeys(password);

    submit.click();

    // exception handling
    if ( BrowserUtils.elementExists(error, Global_VARS.TIMEOUT_SECOND) ) {
        String getError = error.getText();
        throw new Exception("Login Failed with error = " + getError);
    }

}