Add test for compute_opening_fee

Author: tnull

src/lsps2/utils.rs

@@ -55,3 +55,29 @@ pub fn compute_opening_fee(
 		.and_then(|f| f.checked_div(1000000))
 		.map(|f| core::cmp::max(f, opening_fee_min_fee_msat))
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use proptest::prelude::*;
+
+	const MAX_VALUE_MSAT: u64 = 21_000_000_0000_0000_000;
+
+	fn arb_opening_fee_params() -> impl Strategy<Value = (u64, u64, u64)> {
+		(0u64..MAX_VALUE_MSAT, 0u64..MAX_VALUE_MSAT, 0u64..MAX_VALUE_MSAT)
+	}
+
+	proptest! {
+		#[test]
+		fn test_compute_opening_fee((payment_size_msat, opening_fee_min_fee_msat, opening_fee_proportional) in arb_opening_fee_params()) {
+			if let Some(res) = compute_opening_fee(payment_size_msat, opening_fee_min_fee_msat, opening_fee_proportional) {
+				assert!(res >= opening_fee_min_fee_msat);
+				assert_eq!(res as f32, (payment_size_msat as f32 * opening_fee_proportional as f32));
+			} else {
+				// Check we actually overflowed.
+				let max_value = u64::MAX as u128;
+				assert!((payment_size_msat as u128 * opening_fee_proportional as u128) > max_value);
+			}
+		}
+	}
+}