[e2e] Improve su related tests

e2e-tests/resources/broker.resource

@@ -108,19 +108,23 @@ Log In With Remote User Through CLI: Local Password
     Match Text    ${username}@ubuntu:~$    120
 
 
-Try Changing Username In sudo su Log In
-    Hid.Type String    sudo su
+Check That su To Local User Goes To Local Broker
+    Hid.Type String    su ubuntu
     Hid.Keys Combo    Return
-    Try Navigating Back to User Selection
-    Cancel Operation
+    Match Text    Password:    120
+    Hid.Type String    ubuntu    # The password for the local user is the same as the username in our test setup
+    Hid.Keys Combo    Return
+    Match Text    ubuntu@ubuntu:~$    120
 
 
-Try Changing Username In su Log In
+Check That Username Cannot Be Changed When Using su
     [Arguments]    ${username}
     Hid.Type String    su ${username}
     Hid.Keys Combo    Return
     Try Navigating Back to User Selection
     Cancel Operation
+    Match Text    su: Critical error - immediate abort    120
+
 
 Try Navigating Back to User Selection
     # First screen is the autoselected local password mode

e2e-tests/resources/utils.resource

@@ -118,6 +118,11 @@ Close Terminal In Sudo Mode
     Close Focused Window
 
 
+Clear Terminal
+    Hid.Type String    clear
+    Hid.Keys Combo    Return
+
+
 Log Out From Terminal Session
     Match Text    @ubuntu    120
     # We are in a machinectl session, so we need to ^] thrice to exit properly
@@ -176,7 +181,7 @@ Launch App
 
 
 Cancel Operation
-    Hid.Keys Combo    Control_L    C
+    Hid.Keys Combo    Control_L    c
     Match Text    @ubuntu    15
 
 

e2e-tests/tests/login.robot

@@ -33,3 +33,13 @@ Test login with CLI
     # Log in with remote user with local password
     Open Terminal In Sudo Mode
     Log In With Remote User Through CLI: Local Password    ${username}    ${local_password}
+    Log Out From Terminal Session
+    Close Terminal In Sudo Mode
+
+    # Try to change username during su login, it should not be possible
+    Open Terminal
+    Check That Username Cannot Be Changed When Using su    ${username}
+    Clear Terminal
+
+    # Check that `su` to a local user goes to the local broker, not authd.
+    Check That su To Local User Goes To Local Broker