Add `test_p2a_anchor_values_under_trims_and_rounds`

diff --git a/lightning/src/ln/mod.rs b/lightning/src/ln/mod.rs
index 873618b..bae5558 100644
--- a/lightning/src/ln/mod.rs
+++ b/lightning/src/ln/mod.rs
@@ -125,5 +125,7 @@ mod splicing_tests;
 #[cfg(any(test, feature = "_externalize_tests"))]
 #[allow(unused_mut)]
 pub mod update_fee_tests;
+#[cfg(test)]
+mod zero_fee_commitment_tests;
 
 pub use self::peer_channel_encryptor::LN_MAX_MSG_LEN;
diff --git a/lightning/src/ln/zero_fee_commitment_tests.rs b/lightning/src/ln/zero_fee_commitment_tests.rs
new file mode 100644
index 0000000..9d91578
--- /dev/null
+++ b/lightning/src/ln/zero_fee_commitment_tests.rs
@@ -0,0 +1,94 @@
+use crate::ln::chan_utils::shared_anchor_script_pubkey;
+use crate::ln::functional_test_utils::*;
+
+#[test]
+fn test_p2a_anchor_values_under_trims_and_rounds() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let mut user_cfg = test_default_channel_config();
+	user_cfg.channel_handshake_config.our_htlc_minimum_msat = 1;
+	user_cfg.channel_handshake_config.negotiate_anchor_zero_fee_commitments = true;
+	user_cfg.manually_accept_inbound_channels = true;
+
+	let configs = [Some(user_cfg.clone()), Some(user_cfg)];
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &configs);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	let _coinbase_tx = provide_anchor_reserves(&nodes);
+
+	let _node_a_id = nodes[0].node.get_our_node_id();
+	let _node_b_id = nodes[1].node.get_our_node_id();
+
+	const CHAN_CAPACITY: u64 = 10_000_000;
+	let chan_id = create_announced_chan_between_nodes_with_value(
+		&nodes,
+		0,
+		1,
+		CHAN_CAPACITY,
+		(CHAN_CAPACITY / 2) * 1000,
+	)
+	.2;
+
+	macro_rules! p2a_value_test {
+		([$($node_0_1_amt_msat:expr),*], $expected_p2a_value_sat:expr) => {
+			p2a_value_test!([$($node_0_1_amt_msat),*], [], $expected_p2a_value_sat)
+		};
+		([$($node_0_1_amt_msat:expr),*], [$($node_1_0_amt_msat:expr),*], $expected_p2a_value_sat:expr) => {
+			let mut node_0_1_hashes = Vec::new();
+			#[allow(unused_mut)]
+			let mut node_1_0_hashes = Vec::new();
+
+			$(
+				node_0_1_hashes.push(route_payment(&nodes[0], &[&nodes[1]], $node_0_1_amt_msat).1);
+			)*
+			$(
+				node_1_0_hashes.push(route_payment(&nodes[1], &[&nodes[0]], $node_1_0_amt_msat).1);
+			)*
+			let txn = get_local_commitment_txn!(nodes[0], chan_id);
+			assert_eq!(txn.len(), 1);
+			assert_eq!(txn[0].output.iter().find(|output| output.script_pubkey == shared_anchor_script_pubkey()).unwrap().value.to_sat(), $expected_p2a_value_sat);
+			let txn = get_local_commitment_txn!(nodes[1], chan_id);
+			assert_eq!(txn.len(), 1);
+			assert_eq!(txn[0].output.iter().find(|output| output.script_pubkey == shared_anchor_script_pubkey()).unwrap().value.to_sat(), $expected_p2a_value_sat);
+			for hash in node_0_1_hashes {
+				fail_payment(&nodes[0], &[&nodes[1]], hash);
+			}
+			for hash in node_1_0_hashes {
+				fail_payment(&nodes[1], &[&nodes[0]], hash);
+			}
+		};
+	}
+
+	p2a_value_test!([1], 1);
+	p2a_value_test!([238_000], 238);
+	p2a_value_test!([238_001], 239);
+	p2a_value_test!([240_000], 240);
+	p2a_value_test!([240_001], 240);
+	p2a_value_test!([353_000], 240);
+	p2a_value_test!([353_999], 240);
+	p2a_value_test!([354_000], 0);
+	p2a_value_test!([354_001], 1);
+
+	p2a_value_test!([1, 1], 1);
+	p2a_value_test!([1, 999], 1);
+	p2a_value_test!([1, 1000], 2);
+	p2a_value_test!([354_001], 1);
+	p2a_value_test!([354_001, 999], 1);
+	p2a_value_test!([354_001, 1000], 2);
+	p2a_value_test!([354_001, 1999], 2);
+	p2a_value_test!([354_002, 1999], 3);
+
+	p2a_value_test!([1], [1], 2);
+	p2a_value_test!([1], [999], 2);
+	p2a_value_test!([1], [1000], 2);
+	p2a_value_test!([354_001], 1);
+	p2a_value_test!([354_001], [999], 2);
+	p2a_value_test!([354_001], [1000], 2);
+	p2a_value_test!([354_001], [1999], 3);
+	p2a_value_test!([354_002], [1999], 3);
+
+	p2a_value_test!([353_000], [353_000], 240);
+	p2a_value_test!([353_001], [353_000], 240);
+	p2a_value_test!([353_000], [353_001], 240);
+	p2a_value_test!([353_001], [353_001], 240);
+}