fix: add stub for CircuitPython storage module

matrixbox_simulator/device/cpstubs/storage.py

@@ -0,0 +1,36 @@
+"""Stand-in for CircuitPython's `storage`. The simulated filesystem has no
+USB host competing for it, so it starts writable from code's point of view
+and USB drive toggling is a no-op.
+
+https://docs.circuitpython.org/en/latest/shared-bindings/storage/
+"""
+
+
+class VfsFat:
+    def __init__(self, readonly: bool = False) -> None:
+        self.readonly = readonly
+        self.label = "CIRCUITPY"
+
+
+_root_mount = VfsFat()
+
+
+def getmount(mount_path: str) -> VfsFat:
+    return _root_mount
+
+
+def remount(
+    mount_path: str,
+    readonly: bool = False,
+    *,
+    disable_concurrent_write_protection: bool = False,
+) -> None:
+    getmount(mount_path).readonly = readonly
+
+
+def disable_usb_drive() -> None:
+    pass
+
+
+def enable_usb_drive() -> None:
+    pass

tests/test_storage_stub.py

@@ -0,0 +1,13 @@
+from matrixbox_simulator.device.cpstubs import storage
+
+
+def test_root_mount_starts_writable() -> None:
+    assert storage.getmount("/").readonly is False
+
+
+def test_remount_updates_readonly_flag() -> None:
+    storage.remount("/", True)
+    assert storage.getmount("/").readonly is True
+
+    storage.remount("/", False)
+    assert storage.getmount("/").readonly is False