Rename the key action tests

There are actions that relate to editing the input too, which I also want to
test, but I'm not minded to lump them all in the same file. So here I'm
renaming to make it clear these tests are just about movement. The editing
ones will come next in their own file.

tests/input/test_input_key_movement_actions.py

@@ -0,0 +1,159 @@
+"""Unit tests for Input widget position movement actions."""
+
+from textual.app import App, ComposeResult
+from textual.widgets import Input
+
+
+class InputTester(App[None]):
+    """Input widget testing app."""
+
+    def compose(self) -> ComposeResult:
+        for value, input_id in (
+            ("", "empty"),
+            ("Shiny", "single-word"),
+            ("Curse your sudden but inevitable betrayal", "multi-no-punctuation"),
+            (
+                "We have done the impossible, and that makes us mighty.",
+                "multi-punctuation",
+            ),
+            ("Long as she does it quiet-like", "multi-and-hyphenated"),
+        ):
+            yield Input(value, id=input_id)
+
+
+async def test_input_home() -> None:
+    """Going home should always land at position zero."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_home()
+            assert input.cursor_position == 0
+
+
+async def test_input_end() -> None:
+    """Going end should always land at the last position."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_end()
+            assert input.cursor_position == len(input.value)
+
+
+async def test_input_right_from_home() -> None:
+    """Going right should always land at the next position, if there is one."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_cursor_right()
+            assert input.cursor_position == (1 if input.value else 0)
+
+
+async def test_input_right_from_end() -> None:
+    """Going right should always stay put if doing so from the end."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_cursor_right()
+            assert input.cursor_position == len(input.value)
+
+
+async def test_input_left_from_home() -> None:
+    """Going left from home should stay put."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_cursor_left()
+            assert input.cursor_position == 0
+
+
+async def test_input_left_from_end() -> None:
+    """Going left from the end should go back one place, where possible."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_cursor_left()
+            assert input.cursor_position == (len(input.value) - 1 if input.value else 0)
+
+
+async def test_input_left_word_from_home() -> None:
+    """Going left one word from the start should do nothing."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_cursor_left_word()
+            assert input.cursor_position == 0
+
+
+async def test_input_left_word_from_end() -> None:
+    """Going left one word from the end should land correctly.."""
+    async with InputTester().run_test() as pilot:
+        expected_at: dict[str | None, int] = {
+            "empty": 0,
+            "single-word": 0,
+            "multi-no-punctuation": 33,
+            "multi-punctuation": 47,
+            "multi-and-hyphenated": 26,
+        }
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_cursor_left_word()
+            assert input.cursor_position == expected_at[input.id]
+
+
+async def test_input_right_word_from_home() -> None:
+    """Going right one word from the start should land correctly.."""
+    async with InputTester().run_test() as pilot:
+        expected_at: dict[str | None, int] = {
+            "empty": 0,
+            "single-word": 5,
+            "multi-no-punctuation": 6,
+            "multi-punctuation": 3,
+            "multi-and-hyphenated": 5,
+        }
+        for input in pilot.app.query(Input):
+            input.action_cursor_right_word()
+            assert input.cursor_position == expected_at[input.id]
+
+
+async def test_input_right_word_from_end() -> None:
+    """Going right one word from the end should do nothing."""
+    async with InputTester().run_test() as pilot:
+        for input in pilot.app.query(Input):
+            input.action_end()
+            input.action_cursor_right_word()
+            assert input.cursor_position == len(input.value)
+
+
+async def test_input_right_word_to_the_end() -> None:
+    """Using right-word to get to the end should hop the correct number of times."""
+    async with InputTester().run_test() as pilot:
+        expected_hops: dict[str | None, int] = {
+            "empty": 0,
+            "single-word": 1,
+            "multi-no-punctuation": 6,
+            "multi-punctuation": 10,
+            "multi-and-hyphenated": 7,
+        }
+        for input in pilot.app.query(Input):
+            hops = 0
+            while input.cursor_position < len(input.value):
+                input.action_cursor_right_word()
+                hops += 1
+            assert hops == expected_hops[input.id]
+
+
+async def test_input_left_word_from_the_end() -> None:
+    """Using left-word to get home from the end should hop the correct number of times."""
+    async with InputTester().run_test() as pilot:
+        expected_hops: dict[str | None, int] = {
+            "empty": 0,
+            "single-word": 1,
+            "multi-no-punctuation": 6,
+            "multi-punctuation": 10,
+            "multi-and-hyphenated": 7,
+        }
+        for input in pilot.app.query(Input):
+            input.action_end()
+            hops = 0
+            while input.cursor_position:
+                input.action_cursor_left_word()
+                hops += 1
+            assert hops == expected_hops[input.id]
+
+
+# TODO: more tests.