Reduce nesting of macrotest test cases

test_suite/tests/expand/generic_enum.rs

@@ -0,0 +1,9 @@
+use serde::{Serialize, Deserialize};
+
+#[derive(Serialize, Deserialize)]
+pub enum GenericEnum<T, U> {
+    Unit,
+    NewType(T),
+    Seq(T, U),
+    Map { x: T, y: U },
+}