From 78c6c895442a142c13afc602e8c41d7797756c7f Mon Sep 17 00:00:00 2001
From: Will McGugan <willmcgugan@gmail.com>
Date: Wed, 17 Aug 2022 09:17:39 +0100
Subject: [PATCH] added tests for screens

---
 src/textual/app.py    | 20 +++++--------
 tests/test_screens.py | 66 +++++++++++++++++++++++++++++++++++++++++++
 tests/test_view.py    |  6 ----
 3 files changed, 73 insertions(+), 19 deletions(-)
 create mode 100644 tests/test_screens.py
 delete mode 100644 tests/test_view.py

diff --git a/src/textual/app.py b/src/textual/app.py
index 19a5bf7dd..80d12510c 100644
--- a/src/textual/app.py
+++ b/src/textual/app.py
@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 import asyncio
-from datetime import datetime
 import inspect
 import io
 import os
@@ -9,9 +8,11 @@ import platform
 import sys
 import warnings
 from contextlib import redirect_stdout
+from datetime import datetime
 from pathlib import PurePath
 from time import perf_counter
 from typing import (
+    TYPE_CHECKING,
     Any,
     Generic,
     Iterable,
@@ -19,11 +20,10 @@ from typing import (
     TextIO,
     Type,
     TypeVar,
-    TYPE_CHECKING,
 )
 from weakref import WeakSet, WeakValueDictionary
 
-from ._ansi_sequences import SYNC_START, SYNC_END
+from ._ansi_sequences import SYNC_END, SYNC_START
 
 if sys.version_info >= (3, 8):
     from typing import Literal
@@ -39,30 +39,24 @@ from rich.protocol import is_renderable
 from rich.segment import Segments
 from rich.traceback import Traceback
 
-from . import actions
-from . import events
-from . import log
-from . import messages
+from . import actions, events, log, messages
 from ._animator import Animator
 from ._callback import invoke
 from ._context import active_app
-from ._event_broker import extract_handler_actions, NoHandler
+from ._event_broker import NoHandler, extract_handler_actions
 from .binding import Bindings, NoBinding
-from .css.stylesheet import Stylesheet
 from .css.query import NoMatchingNodesError
+from .css.stylesheet import Stylesheet
 from .design import ColorSystem
 from .devtools.client import DevtoolsClient, DevtoolsConnectionError, DevtoolsLog
 from .devtools.redirect_output import StdoutRedirector
 from .dom import DOMNode
 from .driver import Driver
-from .features import parse_features, FeatureFlag
+from .features import FeatureFlag, parse_features
 from .file_monitor import FileMonitor
 from .geometry import Offset, Region, Size
-from .message_pump import MessagePump
 from .reactive import Reactive
 from .renderables.blank import Blank
-from ._profile import timer
-
 from .screen import Screen
 from .widget import Widget
 
diff --git a/tests/test_screens.py b/tests/test_screens.py
new file mode 100644
index 000000000..959b27da3
--- /dev/null
+++ b/tests/test_screens.py
@@ -0,0 +1,66 @@
+import pytest
+
+from textual.app import App, ScreenStackError
+from textual.screen import Screen
+
+
+@pytest.mark.asyncio
+async def test_screens():
+
+    app = App()
+    app._set_active()
+
+    assert not app._installed_screens
+
+    screen1 = Screen(name="screen1")
+    screen2 = Screen(name="screen2")
+    screen3 = Screen(name="screen3")
+
+    # installs screens
+    app.install_screen(screen1, "screen1")
+    app.install_screen(screen2, "screen2")
+
+    # Check they are installed
+    assert app.is_screen_installed("screen1")
+    assert app.is_screen_installed("screen2")
+
+    assert app.get_screen("screen1") is screen1
+    with pytest.raises(KeyError):
+        app.get_screen("foo")
+
+    # Check screen3 is not installed
+    assert not app.is_screen_installed("screen3")
+
+    # Installs screen3
+    app.install_screen(screen3, "screen3")
+    # Confirm installed
+    assert app.is_screen_installed("screen3")
+
+    # Check screen stack is empty
+    assert app.screen_stack == []
+    # Push a screen
+    app.push_screen("screen1")
+    # Check it is on the stack
+    assert app.screen_stack == [screen1]
+    # Check it is current
+    assert app.screen is screen1
+
+    # Switch to another screen
+    app.switch_screen("screen2")
+    # Check it has changed the stack and that it is current
+    assert app.screen_stack == [screen2]
+    assert app.screen is screen2
+
+    # Push another screen
+    app.push_screen("screen3")
+    assert app.screen_stack == [screen2, screen3]
+    assert app.screen is screen3
+
+    # Pop a screen
+    assert app.pop_screen() is screen3
+    assert app.screen is screen2
+    assert app.screen_stack == [screen2]
+
+    # Check we can't pop last screen
+    with pytest.raises(ScreenStackError):
+        app.pop_screen()
diff --git a/tests/test_view.py b/tests/test_view.py
deleted file mode 100644
index 7aa51d33a..000000000
--- a/tests/test_view.py
+++ /dev/null
@@ -1,6 +0,0 @@
-import pytest
-
-from textual.layouts.grid import GridLayout
-from textual.layouts.horizontal import HorizontalLayout
-from textual.layouts.vertical import VerticalLayout
-from textual.screen import Screen