test(#422): add unit tests for transfer holder count update

creator-keys/tests/transfer_holder_count.rs

@@ -0,0 +1,63 @@
+//! Unit tests: transfer must update holder count correctly.
+
+mod contract_test_env;
+use contract_test_env::{
+    register_creator_keys, register_test_creator, test_env_with_auths,
+    set_key_price_for_tests, set_protocol_fee_bps, compute_expected_buy_price,
+};
+use soroban_sdk::{testutils::Address as _, Address};
+
+#[test]
+fn transfer_removes_sender_from_holders_when_balance_reaches_zero() {
+    let env = test_env_with_auths();
+    let (client, _) = register_creator_keys(&env);
+    set_key_price_for_tests(&env, &client, 100i128);
+    set_protocol_fee_bps(&env, &client, 9000u32, 1000u32);
+    let creator = register_test_creator(&env, &client);
+    let sender = Address::generate(&env);
+    let recipient = Address::generate(&env);
+
+    // Buy 1 key for sender
+    let price = compute_expected_buy_price(0, 100i128);
+    client.buy_key(&creator, &sender, &price, &None);
+    let holders_before = client.get_holder_count(&creator);
+    assert!(holders_before > 0);
+
+    // Transfer all keys to recipient
+    client.transfer_key(&creator, &sender, &recipient, &1i128);
+
+    // Sender balance should be zero
+    assert_eq!(client.get_key_balance(&creator, &sender), 0);
+
+    // Holder count should reflect sender removed, recipient added (net zero change)
+    let holders_after = client.get_holder_count(&creator);
+    assert_eq!(holders_before, holders_after,
+        "Holder count unchanged: sender removed, recipient added");
+}
+
+#[test]
+fn transfer_adds_recipient_to_holders_on_first_receipt() {
+    let env = test_env_with_auths();
+    let (client, _) = register_creator_keys(&env);
+    set_key_price_for_tests(&env, &client, 100i128);
+    set_protocol_fee_bps(&env, &client, 9000u32, 1000u32);
+    let creator = register_test_creator(&env, &client);
+    let sender = Address::generate(&env);
+    let new_recipient = Address::generate(&env);
+
+    // Buy 2 keys for sender
+    let price = compute_expected_buy_price(0, 100i128);
+    client.buy_key(&creator, &sender, &price, &None);
+    let price2 = compute_expected_buy_price(1, 100i128);
+    client.buy_key(&creator, &sender, &price2, &None);
+    let holders_before = client.get_holder_count(&creator);
+
+    // Transfer 1 key to new recipient (first time they receive)
+    client.transfer_key(&creator, &sender, &new_recipient, &1i128);
+
+    // Holder count should increase by 1
+    let holders_after = client.get_holder_count(&creator);
+    assert_eq!(holders_after, holders_before + 1,
+        "New recipient added to holder count on first receipt");
+    assert_eq!(client.get_key_balance(&creator, &new_recipient), 1);
+}