Add snapshot test.

tests/snapshot_tests/snapshot_apps/input_suggestions.py

@@ -0,0 +1,22 @@
+from textual.app import App, ComposeResult
+from textual.widgets import Input
+
+
+fruits = ["apple", "pear", "mango", "peach", "strawberry", "blueberry", "banana"]
+
+
+class FruitsApp(App[None]):
+    CSS = """
+    Input > .input--suggestion {
+        color: red;
+        text-style: italic;
+    }
+    """
+
+    def compose(self) -> ComposeResult:
+        yield Input("straw", suggestions=fruits)
+
+
+if __name__ == "__main__":
+    app = FruitsApp()
+    app.run()