diff --git a/src/textual/_text_backend.py b/src/textual/_text_backend.py
index cf2bd0978..9e6cdda87 100644
--- a/src/textual/_text_backend.py
+++ b/src/textual/_text_backend.py
@@ -86,7 +86,7 @@ class TextEditorBackend:
             self.content[: self.cursor_index] + text + self.content[self.cursor_index :]
         )
         self.content = new_text
-        self.cursor_index = min(len(self.content), self.cursor_index + 1)
+        self.cursor_index = min(len(self.content), self.cursor_index + len(text))
         return True
 
     def get_range(self, start: int, end: int) -> str:
diff --git a/tests/test_text_backend.py b/tests/test_text_backend.py
new file mode 100644
index 000000000..b4b98a711
--- /dev/null
+++ b/tests/test_text_backend.py
@@ -0,0 +1,159 @@
+from textual._text_backend import TextEditorBackend
+
+CONTENT = "Hello, world!"
+
+
+def test_set_content():
+    editor = TextEditorBackend()
+    editor.set_content(CONTENT)
+    assert editor.content == CONTENT
+
+
+def test_delete_back_cursor_at_start_is_noop():
+    editor = TextEditorBackend(CONTENT)
+    assert not editor.delete_back()
+    assert editor == TextEditorBackend(CONTENT, 0)
+
+
+def test_delete_back_cursor_at_end():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.cursor_text_end()
+    assert editor.delete_back()
+    assert editor == TextEditorBackend("Hello, world", 12)
+
+
+def test_delete_back_cursor_in_middle():
+    editor = TextEditorBackend(CONTENT, 5)
+    assert editor.delete_back()
+    assert editor == TextEditorBackend("Hell, world!", 4)
+
+
+def test_delete_forward_cursor_at_start():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.delete_forward()
+    assert editor.content == "ello, world!"
+
+
+def test_delete_forward_cursor_at_end_is_noop():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.cursor_text_end()
+    assert not editor.delete_forward()
+    assert editor == TextEditorBackend(CONTENT, len(CONTENT))
+
+
+def test_delete_forward_cursor_in_middle():
+    editor = TextEditorBackend(CONTENT, 5)
+    editor.cursor_index = 5
+    assert editor.delete_forward()
+    assert editor == TextEditorBackend("Hello world!", 5)
+
+
+def test_cursor_left_cursor_at_start_is_noop():
+    editor = TextEditorBackend(CONTENT)
+    assert not editor.cursor_left()
+    assert editor == TextEditorBackend(CONTENT)
+
+
+def test_cursor_left_cursor_in_middle():
+    editor = TextEditorBackend(CONTENT, 6)
+    assert editor.cursor_left()
+    assert editor == TextEditorBackend(CONTENT, 5)
+
+
+def test_cursor_left_cursor_at_end():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    assert editor.cursor_left()
+    assert editor == TextEditorBackend(CONTENT, len(CONTENT) - 1)
+
+
+def test_cursor_right_cursor_at_start():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.cursor_right()
+    assert editor == TextEditorBackend(CONTENT, 1)
+
+
+def test_cursor_right_cursor_in_middle():
+    editor = TextEditorBackend(CONTENT, 5)
+    assert editor.cursor_right()
+    assert editor == TextEditorBackend(CONTENT, 6)
+
+
+def test_cursor_right_cursor_at_end_is_noop():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    editor.cursor_right()
+    assert editor == TextEditorBackend(CONTENT, len(CONTENT))
+
+
+def test_query_cursor_left_cursor_at_start_returns_false():
+    editor = TextEditorBackend(CONTENT)
+    assert not editor.query_cursor_left()
+
+
+def test_query_cursor_left_cursor_at_end_returns_true():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    assert editor.query_cursor_left()
+
+
+def test_query_cursor_left_cursor_in_middle_returns_true():
+    editor = TextEditorBackend(CONTENT, 6)
+    assert editor.query_cursor_left()
+
+
+def test_query_cursor_right_cursor_at_start_returns_true():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.query_cursor_right()
+
+
+def test_query_cursor_right_cursor_in_middle_returns_true():
+    editor = TextEditorBackend(CONTENT, 6)
+    assert editor.query_cursor_right()
+
+
+def test_query_cursor_right_cursor_at_end_returns_false():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    assert not editor.query_cursor_right()
+
+def test_cursor_text_start_cursor_already_at_start():
+    editor = TextEditorBackend(CONTENT)
+    assert not editor.cursor_text_start()
+    assert editor.cursor_index == 0
+
+def test_cursor_text_start_cursor_in_middle():
+    editor = TextEditorBackend(CONTENT, 6)
+    assert editor.cursor_text_start()
+    assert editor.cursor_index == 0
+
+def test_cursor_text_end_cursor_already_at_end():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    assert not editor.cursor_text_end()
+    assert editor.cursor_index == len(CONTENT)
+
+def test_cursor_text_end_cursor_in_middle():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    assert not editor.cursor_text_end()
+    assert editor.cursor_index == len(CONTENT)
+
+
+def test_insert_at_cursor_cursor_at_start():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.insert_at_cursor("ABC")
+    assert editor.content == "ABC" + CONTENT
+    assert editor.cursor_index == len("ABC")
+
+def test_insert_at_cursor_cursor_in_middle():
+    start_cursor_index = 6
+    editor = TextEditorBackend(CONTENT, start_cursor_index)
+    assert editor.insert_at_cursor("ABC")
+    assert editor.content == "Hello,ABC world!"
+    assert editor.cursor_index == start_cursor_index + len("ABC")
+
+
+def test_insert_at_cursor_cursor_at_end():
+    editor = TextEditorBackend(CONTENT, len(CONTENT))
+    assert editor.insert_at_cursor("ABC")
+    assert editor.content == CONTENT + "ABC"
+    assert editor.cursor_index == len(editor.content)
+
+def test_get_range():
+    editor = TextEditorBackend(CONTENT)
+    assert editor.get_range(0, 5) == "Hello"