f make tests a bit more clear as to the paths hit

Author: TheBlueMatt

lightning/src/routing/router.rs

@@ -2372,17 +2372,20 @@ mod tests {
 	}
 
 	#[test]
-	fn overflow_unannounced_path_test_a() {
+	fn overflow_unannounced_path_test_liquidity_underflow() {
 		// Previously, when we had a last-hop hint connected directly to a first-hop channel, where
 		// the last-hop had a value-overflowing fee, we'd panic.
 		// This was due to us adding the first-hop from us unconditionally, causing us to think
 		// we'd built a path (as our node is in the "best candidate" set), when we had not.
+		// In this test, we previously hit a subtraction underflow due to having less available
+		// liquidity at a hop than 0.
 		assert!(do_unannounced_path_test(Some(21_000_000_0000_0000_000), 0, 21_000_000_0000_0000_000, 21_000_000_0000_0000_000).is_err());
 	}
 
 	#[test]
-	fn overflow_unannounced_path_test_b() {
-		// This tests for the same case as above, but with a slightly different codepath.
+	fn overflow_unannounced_path_test_feerate_overflow() {
+		// This tests for the same case as above, except instead of hitting a subtraction
+		// underflow, we hit a case where the fee charged at a hop overflowed.
 		assert!(do_unannounced_path_test(Some(21_000_000_0000_0000_000), 50000, 21_000_000_0000_0000_000, 21_000_000_0000_0000_000).is_err());
 	}