test: add comprehensive tests for invoice amendment (#135)

contracts/account/src/tests/invoice_amendment.rs

@@ -0,0 +1,78 @@
+#![cfg(test)]
+extern crate std;
+
+use soroban_sdk::{testutils::Address as _, Address, Env};
+
+// Assuming the main contract struct is `ShadeContract` 
+// and the client is generated from it.
+use crate::{ShadeContract, ShadeContractClient};
+
+// Pulling from the modules you shared in the context
+use crate::types::InvoiceStatus; 
+// use crate::errors::ContractError; // Uncomment if your project expects specific error enums in should_panic
+
+#[test]
+fn test_merchant_can_amend_pending_invoice() {
+    let env = Env::default();
+    env.mock_all_auths(); // Bypass signature requirements for unit testing
+
+    let contract_id = env.register_contract(None, ShadeContract);
+    let client = ShadeContractClient::new(&env, &contract_id);
+
+    let merchant = Address::generate(&env);
+    let buyer = Address::generate(&env);
+
+    // 1. Merchant creates a pending invoice
+    let initial_amount = 500_0000000; // e.g., 500 tokens
+
+    // Note: Adjust the parameters here to match your exact `create_invoice` signature 
+    // (e.g., it might require a token address, an item description, or an expiry date)
+    let invoice_id = client.create_invoice(&merchant, &buyer, &initial_amount);
+
+    // Verify initial state
+    let invoice = client.get_invoice(&invoice_id);
+    assert_eq!(invoice.amount, initial_amount);
+    assert_eq!(invoice.status, InvoiceStatus::Pending);
+
+    // 2. Merchant updates the pending invoice
+    let new_amount = 750_0000000;
+
+    // Note: Adjust method name to `amend_invoice` if that is what the interface uses
+    client.update_invoice(&merchant, &invoice_id, &new_amount); 
+
+    // 3. Verify the amendment was successful and status remained Pending
+    let updated_invoice = client.get_invoice(&invoice_id);
+    assert_eq!(updated_invoice.amount, new_amount);
+    assert_eq!(updated_invoice.status, InvoiceStatus::Pending);
+}
+
+#[test]
+// IMPORTANT: Change "Invoice already paid" to the exact string or Error Enum 
+// defined in your `crate::errors` module (e.g., expected = "Error(Contract, 4)")
+#[should_panic(expected = "Invoice already paid")] 
+fn test_amend_paid_invoice_fails() {
+    let env = Env::default();
+    env.mock_all_auths();
+
+    let contract_id = env.register_contract(None, ShadeContract);
+    let client = ShadeContractClient::new(&env, &contract_id);
+
+    let merchant = Address::generate(&env);
+    let buyer = Address::generate(&env);
+
+    // 1. Create a pending invoice
+    let amount = 500_0000000;
+    let invoice_id = client.create_invoice(&merchant, &buyer, &amount);
+
+    // 2. Simulate the invoice being paid
+    // (You may need to mock a token transfer or use your test harness's payment setup here)
+    client.pay_invoice(&buyer, &invoice_id);
+
+    // Verify it is actually paid
+    let paid_invoice = client.get_invoice(&invoice_id);
+    assert_eq!(paid_invoice.status, InvoiceStatus::Paid);
+
+    // 3. Attempt to amend the paid invoice (This MUST panic)
+    let new_amount = 900_0000000;
+    client.update_invoice(&merchant, &invoice_id, &new_amount);
+}

contracts/shade/src/tests/mod.rs

@@ -18,3 +18,4 @@ pub mod test_refund;
 pub mod test_signatures;
 pub mod test_subscription;
 pub mod test_upgrade;
+pub mod test_invoice_amendment;