diff --git a/contracts/campaign/src/test.rs b/contracts/campaign/src/test.rs
index 2e1299e..ade4787 100644
--- a/contracts/campaign/src/test.rs
+++ b/contracts/campaign/src/test.rs
@@ -57,3 +57,17 @@ fn test_time_window_validation() {
     let result = client.try_register(&participant2);
     assert!(result.is_err());
 }
+
+#[test]
+fn test_register_participant_twice_returns_false() {
+    let env = Env::default();
+    let contract_id = env.register_contract(None, CampaignContract);
+    let client = CampaignContractClient::new(&env, &contract_id);
+    let admin = Address::generate(&env);
+    let participant = Address::generate(&env);
+    client.initialize(&admin);
+
+    env.mock_all_auths();
+    assert!(client.register(&participant));
+    assert!(!client.register(&participant));
+}
diff --git a/contracts/rewards/src/test.rs b/contracts/rewards/src/test.rs
index f910be1..2156730 100644
--- a/contracts/rewards/src/test.rs
+++ b/contracts/rewards/src/test.rs
@@ -54,11 +54,13 @@ fn test_metadata() {
 }
 
 #[test]
+fn test_claim_more_than_balance_errors() {
 fn test_batch_credit() {
     let env = Env::default();
     let contract_id = env.register_contract(None, RewardsContract);
     let client = RewardsContractClient::new(&env, &contract_id);
     let admin = Address::generate(&env);
+    let user = Address::generate(&env);
     let user_a = Address::generate(&env);
     let user_b = Address::generate(&env);
     client.initialize(
@@ -68,6 +70,13 @@ fn test_batch_credit() {
     );
 
     env.mock_all_auths();
+    let result = client.try_claim(&user, &1);
+    assert!(result.is_err());
+    assert_eq!(client.balance(&user), 0);
+}
+
+#[test]
+fn test_credit_overflow_errors() {
     let recipients = soroban_sdk::vec![
         &env,
         (user_a.clone(), 50u64),
@@ -86,6 +95,7 @@ fn test_batch_credit_is_atomic_on_overflow() {
     let contract_id = env.register_contract(None, RewardsContract);
     let client = RewardsContractClient::new(&env, &contract_id);
     let admin = Address::generate(&env);
+    let user = Address::generate(&env);
     let user_a = Address::generate(&env);
     let user_b = Address::generate(&env);
     client.initialize(
@@ -95,6 +105,23 @@ fn test_batch_credit_is_atomic_on_overflow() {
     );
 
     env.mock_all_auths();
+    client.credit(&admin, &user, &u64::MAX);
+
+    let result = client.try_credit(&admin, &user, &1);
+    assert!(result.is_err());
+    assert_eq!(client.balance(&user), u64::MAX);
+}
+
+#[test]
+fn test_uninitialized_access_returns_defaults() {
+    let env = Env::default();
+    let contract_id = env.register_contract(None, RewardsContract);
+    let client = RewardsContractClient::new(&env, &contract_id);
+    let user = Address::generate(&env);
+
+    assert_eq!(client.metadata(), (symbol_short!("Trivela"), symbol_short!("TVL")));
+    assert_eq!(client.balance(&user), 0);
+    assert_eq!(client.total_claimed(), 0);
     client.credit(&admin, &user_a, &10);
     client.credit(&admin, &user_b, &u64::MAX);