headless driver and tests

src/textual/drivers/headless_driver.py

@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+
+from ..driver import Driver
+
+
+class HeadlessDriver(Driver):
+    """A do-nothing driver for testing."""
+
+    def start_application_mode(self) -> None:
+        pass
+
+    def disable_input(self) -> None:
+        pass
+
+    def stop_application_mode(self) -> None:
+        pass

tests/test_auto_refresh.py

@@ -0,0 +1,30 @@
+from time import time
+
+from textual.app import App
+
+
+class RefreshApp(App[float]):
+    def __init__(self):
+        self.count = 0
+        super().__init__()
+
+    def on_mount(self):
+        self.start = time()
+        self.auto_refresh = 0.1
+
+    def _automatic_refresh(self):
+        self.count += 1
+        super()._automatic_refresh()
+
+    def refresh(self, *, repaint: bool = True, layout: bool = False) -> None:
+        super().refresh(repaint=repaint, layout=layout)
+        if self.count == 3:
+            self.exit(time() - self.start)
+
+
+def test_auto_refresh():
+    app = RefreshApp()
+
+    elapsed = app.run(quit_after=0.5, headless=True)
+    assert elapsed is not None
+    assert elapsed >= 0.3 and elapsed < 0.31