Start Input unit tests for actions that modify the text

tests/input/test_input_key_modification_actions.py

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+"""Unit tests for Input widget value modification actions."""
+
+from textual.app import App, ComposeResult
+from textual.widgets import Input
+
+
+TEST_INPUTS: dict[str | None, str] = {
+    "empty": "",
+    "multi-no-punctuation": "Curse your sudden but inevitable betrayal",
+    "multi-punctuation": "We have done the impossible, and that makes us mighty.",
+    "multi-and-hyphenated": "Long as she does it quiet-like",
+}
+
+
+class InputTester(App[None]):
+    """Input widget testing app."""
+
+    def compose(self) -> ComposeResult:
+        for input_id, value in TEST_INPUTS.items():
+            yield Input(value, id=input_id)
+
+
+async def test_delete_left_from_home() -> None:
+    """Deleting left from home should do nothing."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_delete_left()
+            assert input.cursor_position == 0
+            assert input.value == TEST_INPUTS[input.id]
+
+
+async def test_delete_left_from_end() -> None:
+    """Deleting left from home should do remove the last character (if there is one)."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_delete_left()
+            assert input.cursor_position == len(input.value)
+            assert input.value == TEST_INPUTS[input.id][:-1]
+
+
+async def test_delete_left_word_from_home() -> None:
+    """Deleting word left from home should do nothing."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_delete_left_word()
+            assert input.cursor_position == 0
+            assert input.value == TEST_INPUTS[input.id]
+
+
+async def test_delete_left_word_from_end() -> None:
+    """Deleting word left from end should remove the expected text."""
+    async with InputTester().run_test() as pilot:
+        expected: dict[str | None, str] = {
+            "empty": "",
+            "multi-no-punctuation": "Curse your sudden but inevitable ",
+            "multi-punctuation": "We have done the impossible, and that makes us ",
+            "multi-and-hyphenated": "Long as she does it quiet-",
+        }
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_delete_left_word()
+            assert input.cursor_position == len(input.value)
+            assert input.value == expected[input.id]
+
+
+async def test_delete_left_all_from_home() -> None:
+    """Deleting all left from home should do nothing."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_delete_left_all()
+            assert input.cursor_position == 0
+            assert input.value == TEST_INPUTS[input.id]
+
+
+async def test_delete_left_all_from_end() -> None:
+    """Deleting all left from end should empty the input value."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_delete_left_all()
+            assert input.cursor_position == 0
+            assert input.value == ""