refactor(test): eliminate overcomplicated state machine

In test_serial_console_login, we were implementing something that takes
three lines (send and receive data via serial) via an overcomplicated
state machine system. Eliminate the 100 lines of state machine code and
instead just... do the 3 lines of serial.tx/rx.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

tests/framework/state_machine.py

@@ -11,40 +11,10 @@
 
 from framework import utils
 from framework.microvm import Serial
-from framework.state_machine import TestState
 
 PLATFORM = platform.machine()
 
 
-class WaitTerminal(TestState):
-    """Initial state when we wait for the login prompt."""
-
-    def handle_input(self, serial, input_char) -> TestState:
-        """Handle input and return next state."""
-        if self.match(input_char):
-            serial.tx("id")
-            return WaitIDResult("uid=0(root) gid=0(root) groups=0(root)")
-        return self
-
-
-class WaitIDResult(TestState):
-    """Wait for the console to show the result of the 'id' shell command."""
-
-    def handle_input(self, unused_serial, input_char) -> TestState:
-        """Handle input and return next state."""
-        if self.match(input_char):
-            return TestFinished()
-        return self
-
-
-class TestFinished(TestState):
-    """Test complete and successful."""
-
-    def handle_input(self, unused_serial, _) -> TestState:
-        """Return self since the test is about to end."""
-        return self
-
-
 def test_serial_after_snapshot(uvm_plain, microvm_factory):
     """
     Serial I/O after restoring from a snapshot.
@@ -104,11 +74,9 @@ def test_serial_console_login(uvm_plain_any):
 
     serial = Serial(microvm)
     serial.open()
-    current_state = WaitTerminal("ubuntu-fc-uvm:")
-
-    while not isinstance(current_state, TestFinished):
-        output_char = serial.rx_char()
-        current_state = current_state.handle_input(serial, output_char)
+    serial.rx("ubuntu-fc-uvm:")
+    serial.tx("id")
+    serial.rx("uid=0(root) gid=0(root) groups=0(root)")
 
 
 def get_total_mem_size(pid):