diff --git a/tests/css/test_mega_stylesheet.css b/tests/css/test_mega_stylesheet.css
new file mode 100644
index 000000000..13005ead9
--- /dev/null
+++ b/tests/css/test_mega_stylesheet.css
@@ -0,0 +1,227 @@
+/*
+ * The idea with this stylesheet is that it should contain as many valid
+ * ways of styling things as possible. So, as time goes on, feel free to add
+ * something to here. Be creative. Do the wildest things you can think of.
+ */
+
+* {}
+* * {}
+* * * {}
+* > * {}
+* > * > * {}
+
+/**********************************************************************/
+
+A {}
+A A {}
+A A A {}
+A > A {}
+A > A > A {}
+
+A1 {}
+A1 A1 {}
+A1 A1 A1 {}
+A1 > A1 {}
+A1 > A1 > A1 {}
+
+A {}
+A A1 {}
+A A1 A1 {}
+A > A1 {}
+A > A1 > A1 {}
+
+A1 {}
+A1 A {}
+A1 A A {}
+A1 > A {}
+A1 > A > A {}
+
+/**********************************************************************/
+
+A {}
+A, A {}
+A,A {}
+A, A, A {}
+A,A,A {}
+A , A , A {}
+A
+,
+A
+,
+A
+{
+
+}
+
+A1 {}
+A1, A1 {}
+A1,A1 {}
+A1, A1, A1 {}
+A1,A1,A1 {}
+A1 , A1 , A1 {}
+A1
+,
+A1
+,
+A1
+{
+
+}
+
+/**********************************************************************/
+
+.A {}
+.A .A {}
+.A .A .A {}
+.A > .A {}
+.A > .A > .A {}
+
+.A1 {}
+.A1 .A1 {}
+.A1 .A1 .A1 {}
+.A1 > .A1 {}
+.A1 > .A1 > .A1 {}
+
+.A1 {}
+.A1 .A {}
+.A1 .A .A {}
+.A1 > .A {}
+.A1 > .A > .A {}
+
+.A {}
+.A .A1 {}
+.A .A1 .A1 {}
+.A > .A1 {}
+.A > .A1 > .A1 {}
+
+/**********************************************************************/
+
+.A {}
+.A.A {}
+.A.A.A {}
+
+.A1 {}
+.A1.A1 {}
+.A1.A1.A1 {}
+
+.A1 {}
+.A1.A {}
+.A1.A.A {}
+
+.A {}
+.A.A1 {}
+.A.A1.A1 {}
+
+/**********************************************************************/
+
+#A {}
+#A #A {}
+#A #A #A {}
+#A > #A {}
+#A > #A > #A {}
+
+#A1 {}
+#A1 #A1 {}
+#A1 #A1 #A1 {}
+#A1 > #A1 {}
+#A1 > #A1 > #A1 {}
+
+#A1 {}
+#A1 #A {}
+#A1 #A #A {}
+#A1 > #A {}
+#A1 > #A > #A {}
+
+#A {}
+#A #A1 {}
+#A #A1 #A1 {}
+#A > #A1 {}
+#A > #A1 > #A1 {}
+
+/**********************************************************************/
+
+A:foo {}
+A:foo:bar {}
+A
+:foo {}
+A
+:foo:bar {}
+A
+:foo
+:bar {}
+A:foo-bar {}
+A
+:foo-bar {}
+
+A :foo {}
+A :foo :bar {}
+A :foo-bar {}
+
+.A:foo {}
+.A:foo:bar {}
+.A
+:foo {}
+.A
+:foo:bar {}
+.A
+:foo
+:bar {}
+.A:foo-bar {}
+.A
+:foo-bar {}
+
+#A:foo {}
+#A:foo:bar {}
+#A
+:foo {}
+#A
+:foo:bar {}
+#A
+:foo
+:bar {}
+#A:foo-bar {}
+#A
+:foo-bar {}
+
+A1.A1.A1:foo {}
+A1.A1#A1:foo {}
+A1:foo.A1:foo#A1:foo {}
+
+/**********************************************************************/
+
+$foo:;
+$foo:1;
+$fo1:1;
+$1:1;
+$-:1;
+$--:1;
+$--------------------------------------------------:1;
+$-1:1;
+$--1:1;
+$--------------------------------------------------1:1;
+$_1:1;
+$__1:1;
+$__________________________________________________1:1;
+
+/**********************************************************************/
+A{}
+A {
+}
+A {} A {} A {}
+A{}A{}A{}
+A {
+} A {} A {
+}
+A
+{}
+A
+{
+
+}
+
+/**********************************************************************
+ * Don't change or remove this. This class is looked for in the unit
+ * test code to make sure that everything parsed.
+ */
+.---we-made-it-to-the-end--- {
+}
diff --git a/tests/css/test_mega_stylesheet.py b/tests/css/test_mega_stylesheet.py
new file mode 100644
index 000000000..6cfaf2868
--- /dev/null
+++ b/tests/css/test_mega_stylesheet.py
@@ -0,0 +1,11 @@
+from pathlib import Path
+
+from textual.css.stylesheet import Stylesheet
+
+
+def test_mega_stylesheet() -> None:
+    """It should be possible to load a known-good stylesheet."""
+    mega_stylesheet = Stylesheet()
+    mega_stylesheet.read(Path(__file__).parent / "test_mega_stylesheet.css")
+    mega_stylesheet.parse()
+    assert ".---we-made-it-to-the-end---" in mega_stylesheet.css