Test Wasm execution for alloc test contract (#1452)

### What
Add Wasm-based testing for the allocation contract alongside the native
tests.

### Why
Testing both native and Wasm implementations ensures the contract
behaves consistently regardless of execution environment. Makes sure
that the alloc functionality works correctly in the actual Wasm VM,
which the contract is built to the wasm target for.

Author: leighmcculloch

tests/alloc/src/lib.rs

@@ -21,19 +21,4 @@ impl Contract {
     }
 }
 
-#[cfg(test)]
-mod test {
-    use soroban_sdk::{vec, Env};
-
-    use crate::{Contract, ContractClient};
-
-    #[test]
-    fn test_add() {
-        let e = Env::default();
-        let contract_id = e.register(Contract, ());
-        let client = ContractClient::new(&e, &contract_id);
-
-        let list = client.num_list(&5);
-        assert_eq!(list, vec![&e, 0, 1, 2, 3, 4])
-    }
-}
+mod test;

tests/alloc/src/test.rs

@@ -0,0 +1,43 @@
+#![cfg(test)]
+use soroban_sdk::{testutils::EnvTestConfig, vec, Env};
+
+use crate::{Contract, ContractClient};
+
+mod imported {
+    soroban_sdk::contractimport!(
+        file = "../../target/wasm32-unknown-unknown/release/test_alloc.wasm"
+    );
+}
+
+macro_rules! tests {
+    ($context:ident, $contract:expr) => {
+        mod $context {
+            use super::*;
+
+            #[test]
+            fn test() {
+                let e = Env::new_with_config(EnvTestConfig {
+                    // Disable test snapshots because the tests in this repo will run across
+                    // multiple hosts, and this test uses a wasm file that won't build consistently
+                    // across different hosts.
+                    capture_snapshot_at_drop: false,
+                });
+                let contract_id = e.register($contract, ());
+                let client = ContractClient::new(&e, &contract_id);
+
+                let list = client.num_list(&50);
+                assert_eq!(
+                    list,
+                    vec![
+                        &e, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
+                        20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38,
+                        39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49,
+                    ]
+                )
+            }
+        }
+    };
+}
+
+tests!(native, Contract);
+tests!(wasm, imported::WASM);