[Enhancement] Enable flow-based test scenarios

docs/manual_installation.md

@@ -177,6 +177,7 @@ cd seedsigner
 ```bash
 # Takes 1hr 45min on a Pi Zero 1.3
 pip install -r requirements.txt
+pip install -r requirements-raspi.txt
 ```
 
 #### `pyzbar`

requirements-raspi.txt

@@ -0,0 +1,3 @@
+picamera==1.13
+RPi.GPIO==0.7.0
+spidev==3.5

requirements.txt

@@ -1,10 +1,7 @@
 embit==0.7.0
 numpy==1.21.1
-picamera==1.13
 Pillow==8.2.0
 -e git+https://github.com/seedsigner/pyzbar.git@c3c237821c6a20b17953efe59b90df0b514a1c03#egg=pyzbar
 qrcode==7.3.1
-RPi.GPIO==0.7.0
 six==1.16.0
-spidev==3.5
 urtypes @ git+https://github.com/selfcustody/urtypes.git@7fb280eab3b3563dfc57d2733b0bf5cbc0a96a6a

src/seedsigner/controller.py

@@ -32,6 +32,23 @@ def __repr__(self):
 
 
 
+class StopFlowBasedTest(Exception):
+    """
+        This is a special exception that is only raised by the test suite to stop the
+        Controller's main loop. It should not be raised by any other code.
+    """
+    pass
+
+
+class FlowBasedTestException(Exception):
+    """
+        This is a special exception that is only raised by the test suite.
+        It should not be raised by any other code.
+    """
+    pass
+
+
+
 class Controller(Singleton):
     """
         The Controller is a globally available singleton that maintains SeedSigner state.
@@ -185,7 +202,13 @@ def clear_back_stack(self):
         self.back_stack = BackStack()
 
 
-    def start(self) -> None:
+    def start(self, initial_destination: Destination = None) -> None:
+        """
+            The main loop of the application.
+
+            * initial_destination: The first View to run. If None, the MainMenuView is
+            used. Only used by the test suite.
+        """
         from .views import MainMenuView, BackStackView
         from .views.screensaver import OpeningSplashScreen
 
@@ -218,7 +241,10 @@ def run(self):
                 View_cls(**init_args).run()
         """
         try:
-            next_destination = Destination(MainMenuView)
+            if initial_destination:
+                next_destination = initial_destination
+            else:
+                next_destination = Destination(MainMenuView)
             while True:
                 # Destination(None) is a special case; render the Home screen
                 if next_destination.View_cls is None:
@@ -240,10 +266,24 @@ def run(self):
                 print(f"back_stack: {self.back_stack}")
 
                 try:
+                    # Instantiate the View class and run it
                     print(f"Executing {next_destination}")
                     next_destination = next_destination.run()
+
+                except StopFlowBasedTest:
+                    # This is a special exception that is only raised by the test suite
+                    # to stop the Controller loop and exit the test.
+                    return
+
+                except FlowBasedTestException as e:
+                    # This is a special exception that is only raised by the test suite.
+                    # Re-raise so the test suite can handle it.
+                    raise e
+
                 except Exception as e:
                     # Display user-friendly error screen w/debugging info
+                    import traceback
+                    traceback.print_exc()
                     next_destination = self.handle_exception(e)
 
                 if not next_destination:

src/seedsigner/models/settings_definition.py

@@ -217,7 +217,7 @@ class SettingsEntry:
     visibility: str = SettingsConstants.VISIBILITY__GENERAL
     type: str = SettingsConstants.TYPE__ENABLED_DISABLED
     help_text: str = None
-    selection_options: List[str] = None
+    selection_options: list[tuple[str | int], str] = None
     default_value: Any = None
 
     def __post_init__(self):