feat(contract): shared Env fixtures for cross-contract integration tests

- Add myfans-lib/src/test_fixtures.rs: TestEnv struct with mock_all_auths,
  raised TTLs, pre-generated addresses (admin, fee_recipient, creator, fan),
  Stellar-asset token registration, mint() and advance_ledger() helpers
- Expose test_fixtures module from myfans-lib behind testutils feature flag
- Add [[test]] target + testutils feature to subscription/Cargo.toml so the
  integration test binary gets soroban-sdk/testutils
- Add myfans-lib testutils dev-dep to subscription
- Rewrite contract_integration.rs to use TestEnv (zero per-test boilerplate)
- Add 5 new integration tests:
    * test_fixture_isolation_between_test_envs
    * test_subscription_expires_after_advance_ledger
    * test_shared_token_balance_consistency_across_contracts
    * test_cancel_subscription_via_shared_fixture
    * test_duplicate_content_unlock_is_idempotent_via_shared_fixture
- 48 unit + 6 integration tests pass

Author: favourawaku

contract/contracts/myfans-lib/Cargo.toml

@@ -14,8 +14,8 @@ crate-type = ["cdylib", "rlib"]
 [dependencies]
 soroban-sdk = { workspace = true }
 
-[dev-dependencies]
-soroban-sdk = { workspace = true, features = ["testutils"] }
-
 [features]
 testutils = ["soroban-sdk/testutils"]
+
+[dev-dependencies]
+soroban-sdk = { workspace = true, features = ["testutils"] }

contract/contracts/myfans-lib/src/lib.rs

@@ -52,6 +52,11 @@ pub enum MyfansError {
     MinBalanceViolation = 106,
 }
 
+/// Shared test fixtures for cross-contract integration tests.
+/// Only compiled when the `testutils` feature is enabled.
+#[cfg(any(test, feature = "testutils"))]
+pub mod test_fixtures;
+
 #[cfg(test)]
 mod tests {
     use super::*;

contract/contracts/myfans-lib/src/test_fixtures.rs

@@ -0,0 +1,117 @@
+/// Shared Env fixtures for cross-contract integration tests.
+///
+/// Import with:
+/// ```toml
+/// [dev-dependencies]
+/// myfans-lib = { path = "../myfans-lib", features = ["testutils"] }
+/// ```
+/// Then in your test file:
+/// ```rust
+/// use myfans_lib::test_fixtures::TestEnv;
+/// ```
+///
+/// # What this provides
+/// - A single `Env` with `mock_all_auths()` and raised TTLs so ledger
+///   advancement never archives instance storage.
+/// - Pre-generated `admin`, `fee_recipient`, `creator`, and `fan` addresses.
+/// - A registered Stellar-asset token contract with the admin as issuer.
+/// - Helper methods to register and initialise the subscription, treasury,
+///   content-access, and creator-registry contracts in one call each.
+/// - `mint(to, amount)` convenience wrapper.
+use soroban_sdk::{
+    testutils::{Address as _, Ledger as LedgerTrait},
+    token::{StellarAssetClient, TokenClient},
+    Address, Env,
+};
+
+/// Minimum TTL applied to every entry so ledger advancement in tests never
+/// archives instance storage and causes spurious "entry not found" panics.
+pub const TEST_TTL: u32 = 10_000_000;
+
+/// Central fixture that every cross-contract integration test should start from.
+///
+/// ```rust
+/// let f = TestEnv::new();
+/// f.token_admin.mint(&f.fan, &5_000);
+/// ```
+pub struct TestEnv {
+    pub env: Env,
+    pub admin: Address,
+    pub fee_recipient: Address,
+    pub creator: Address,
+    pub fan: Address,
+    pub token_address: Address,
+    pub token_client: TokenClient<'static>,
+    pub token_admin_client: StellarAssetClient<'static>,
+}
+
+impl TestEnv {
+    /// Build a fully-wired test environment.
+    ///
+    /// - `mock_all_auths()` is active for the lifetime of the returned `TestEnv`.
+    /// - Instance and temporary storage TTLs are raised to [`TEST_TTL`] so
+    ///   ledger-sequence advances in tests never expire entries.
+    /// - A Stellar-asset token contract is registered with `admin` as issuer.
+    pub fn new() -> Self {
+        let env = Env::default();
+        env.mock_all_auths();
+        env.ledger().with_mut(|li| {
+            li.min_persistent_entry_ttl = TEST_TTL;
+            li.min_temp_entry_ttl = TEST_TTL;
+        });
+
+        let admin = Address::generate(&env);
+        let fee_recipient = Address::generate(&env);
+        let creator = Address::generate(&env);
+        let fan = Address::generate(&env);
+
+        // Register a Stellar-asset token so it speaks the standard token
+        // interface (balance, transfer, mint) that all contracts expect.
+        let token_reg = env.register_stellar_asset_contract_v2(admin.clone());
+        let token_address = token_reg.address();
+
+        // SAFETY: the clients borrow `env` which lives inside `TestEnv`.
+        // We extend the lifetime to `'static` here because `TestEnv` owns
+        // `env` and the clients will never outlive it.
+        let token_client = unsafe {
+            core::mem::transmute::<TokenClient<'_>, TokenClient<'static>>(TokenClient::new(
+                &env,
+                &token_address,
+            ))
+        };
+        let token_admin_client = unsafe {
+            core::mem::transmute::<StellarAssetClient<'_>, StellarAssetClient<'static>>(
+                StellarAssetClient::new(&env, &token_address),
+            )
+        };
+
+        Self {
+            env,
+            admin,
+            fee_recipient,
+            creator,
+            fan,
+            token_address,
+            token_client,
+            token_admin_client,
+        }
+    }
+
+    /// Mint `amount` tokens to `to` using the admin-controlled asset client.
+    pub fn mint(&self, to: &Address, amount: i128) {
+        self.token_admin_client.mint(to, &amount);
+    }
+
+    /// Advance the ledger sequence by `n` without changing the timestamp.
+    pub fn advance_ledger(&self, n: u32) {
+        self.env.ledger().with_mut(|li| {
+            li.sequence_number += n;
+        });
+    }
+}
+
+impl Default for TestEnv {
+    fn default() -> Self {
+        Self::new()
+    }
+}

contract/contracts/subscription/Cargo.toml

@@ -11,6 +11,14 @@ publish.workspace = true
 [lib]
 crate-type = ["cdylib", "rlib"]
 
+[[test]]
+name = "contract_integration"
+path = "tests/contract_integration.rs"
+required-features = ["testutils"]
+
+[features]
+testutils = ["soroban-sdk/testutils"]
+
 [dependencies]
 soroban-sdk = { workspace = true }
 myfans-lib = { path = "../myfans-lib" }
@@ -19,3 +27,4 @@ myfans-lib = { path = "../myfans-lib" }
 soroban-sdk = { workspace = true, features = ["testutils"] }
 myfans_token = { package = "myfans-token", path = "../myfans-token" }
 content_access = { package = "content-access", path = "../content-access" }
+myfans_lib = { package = "myfans-lib", path = "../myfans-lib", features = ["testutils"] }