chore: add arbitrary order macro for more resilient subsystem tests

node/subsystem-util/src/lib.rs

@@ -752,3 +752,33 @@ where
 		SpawnedSubsystem { name: Job::NAME.strip_suffix("Job").unwrap_or(Job::NAME), future }
 	}
 }
+
+/// Asserts that two patterns match, yet only one
+#[macro_export]
+macro_rules! arbitrary_order {
+	($rx:expr; $p1:pat => $e1:expr; $p2:pat => $e2:expr) => {
+		// If i.e. a enum has only two variants, `_` is unreachable.
+		match $rx {
+			$p1 => {
+				let __ret1 = { $e1 };
+				let __ret2 = match $rx {
+					$p2 => $e2,
+					#[allow(unreachable_patterns)]
+					_ => unreachable!("first pattern matched, second pattern did not"),
+				};
+				(__ret1, __ret2)
+			},
+			$p2 => {
+				let __ret2 = { $e2 };
+				let __ret1 = match $rx {
+					$p1 => $e1,
+					#[allow(unreachable_patterns)]
+					_ => unreachable!("second pattern matched, first pattern did not"),
+				};
+				(__ret1, __ret2)
+			},
+			#[allow(unreachable_patterns)]
+			_ => unreachable!("neither first nor second pattern matched"),
+		}
+	};
+}

node/subsystem-util/src/tests.rs

@@ -245,3 +245,19 @@ fn tick_tack_metronome() {
 		)
 	});
 }
+
+#[test]
+fn macro_arbitrary_order() {
+	let mut vals = vec![Some(15_usize), None];
+	let (first, second) = arbitrary_order!(vals.pop().unwrap(); Some(fx) => fx; None => 0);
+	assert_eq!(first, 15_usize);
+	assert_eq!(second, 0_usize);
+}
+
+#[test]
+fn macro_arbitrary_order_swapped() {
+	let mut vals = vec![None, Some(11_usize)];
+	let (first, second) = arbitrary_order!(vals.pop().unwrap(); Some(fx) => fx; None => 0);
+	assert_eq!(first, 11_usize);
+	assert_eq!(second, 0);
+}