diff --git a/crates/miyabi-core/src/cache.rs b/crates/miyabi-core/src/cache.rs
index fea85a7..1d33f67 100644
--- a/crates/miyabi-core/src/cache.rs
+++ b/crates/miyabi-core/src/cache.rs
@@ -237,4 +237,214 @@ mod tests {
         assert_eq!(key1, key2);
         assert_ne!(key1, key3);
     }
+
+    #[test]
+    fn test_cache_entry_creation() {
+        let entry = CacheEntry::new("test_value", Duration::from_secs(60));
+        assert_eq!(entry.value, "test_value");
+        assert!(!entry.is_expired());
+    }
+
+    #[test]
+    fn test_cache_entry_expired() {
+        let entry = CacheEntry::new("test_value", Duration::from_millis(0));
+        std::thread::sleep(Duration::from_millis(10));
+        assert!(entry.is_expired());
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_insert_with_custom_ttl() {
+        let cache = TTLCache::new(Duration::from_secs(3600)); // default 1 hour
+
+        // Insert with shorter custom TTL
+        cache.insert_with_ttl("key1", "value1", Duration::from_millis(50)).await;
+        assert_eq!(cache.get(&"key1").await, Some("value1"));
+
+        sleep(Duration::from_millis(100)).await;
+        assert_eq!(cache.get(&"key1").await, None);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_remove() {
+        let cache = TTLCache::new(Duration::from_secs(3600));
+
+        cache.insert("key1", "value1").await;
+        assert_eq!(cache.get(&"key1").await, Some("value1"));
+
+        let removed = cache.remove(&"key1").await;
+        assert_eq!(removed, Some("value1"));
+        assert_eq!(cache.get(&"key1").await, None);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_remove_nonexistent() {
+        let cache: TTLCache<String, String> = TTLCache::new(Duration::from_secs(3600));
+        let removed = cache.remove(&"nonexistent".to_string()).await;
+        assert_eq!(removed, None);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_stats() {
+        let cache = TTLCache::new(Duration::from_millis(100));
+
+        cache.insert("key1", "value1").await;
+        cache.insert("key2", "value2").await;
+
+        let stats = cache.stats().await;
+        assert_eq!(stats.total_entries, 2);
+        assert_eq!(stats.active_entries, 2);
+        assert_eq!(stats.expired_entries, 0);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_stats_with_expired() {
+        let cache = TTLCache::new(Duration::from_millis(50));
+
+        cache.insert("key1", "value1").await;
+        cache.insert_with_ttl("key2", "value2", Duration::from_secs(3600)).await;
+
+        sleep(Duration::from_millis(100)).await;
+
+        let stats = cache.stats().await;
+        assert_eq!(stats.total_entries, 2);
+        assert_eq!(stats.expired_entries, 1);
+        assert_eq!(stats.active_entries, 1);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_clear() {
+        let cache = TTLCache::new(Duration::from_secs(3600));
+
+        cache.insert("key1", "value1").await;
+        cache.insert("key2", "value2").await;
+
+        let stats = cache.stats().await;
+        assert_eq!(stats.total_entries, 2);
+
+        cache.clear().await;
+
+        let stats = cache.stats().await;
+        assert_eq!(stats.total_entries, 0);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_multiple_types() {
+        let cache: TTLCache<i32, String> = TTLCache::new(Duration::from_secs(3600));
+
+        cache.insert(1, "one".to_string()).await;
+        cache.insert(2, "two".to_string()).await;
+
+        assert_eq!(cache.get(&1).await, Some("one".to_string()));
+        assert_eq!(cache.get(&2).await, Some("two".to_string()));
+    }
+
+    #[test]
+    fn test_llm_cache_key_without_temperature() {
+        let key1 = LLMCacheKey::new("prompt", "model", None);
+        let key2 = LLMCacheKey::new("prompt", "model", None);
+        let key3 = LLMCacheKey::new("prompt", "model", Some(0.5));
+
+        assert_eq!(key1, key2);
+        assert_ne!(key1, key3);
+        assert!(key1.temperature.is_none());
+        assert!(key3.temperature.is_some());
+    }
+
+    #[test]
+    fn test_llm_cache_key_different_models() {
+        let key1 = LLMCacheKey::new("prompt", "claude-3-sonnet", Some(0.7));
+        let key2 = LLMCacheKey::new("prompt", "claude-3-opus", Some(0.7));
+
+        assert_ne!(key1, key2);
+        assert_eq!(key1.model, "claude-3-sonnet");
+        assert_eq!(key2.model, "claude-3-opus");
+    }
+
+    #[test]
+    fn test_api_cache_key_creation() {
+        let key1 = ApiCacheKey::new("/api/v1/messages", "{\"prompt\":\"test\"}");
+        let key2 = ApiCacheKey::new("/api/v1/messages", "{\"prompt\":\"test\"}");
+        let key3 = ApiCacheKey::new("/api/v1/messages", "{\"prompt\":\"different\"}");
+
+        assert_eq!(key1.endpoint, "/api/v1/messages");
+        assert_eq!(key1, key2);
+        assert_ne!(key1, key3);
+    }
+
+    #[test]
+    fn test_api_cache_key_different_endpoints() {
+        let key1 = ApiCacheKey::new("/api/v1/messages", "{}");
+        let key2 = ApiCacheKey::new("/api/v2/messages", "{}");
+
+        assert_ne!(key1, key2);
+    }
+
+    #[test]
+    fn test_create_llm_cache() {
+        let cache = create_llm_cache();
+        // Default TTL is 1 hour
+        assert_eq!(cache.default_ttl, Duration::from_secs(3600));
+    }
+
+    #[test]
+    fn test_create_api_cache() {
+        let cache = create_api_cache();
+        // Default TTL is 30 minutes
+        assert_eq!(cache.default_ttl, Duration::from_secs(1800));
+    }
+
+    #[test]
+    fn test_cache_stats_serialization() {
+        let stats = CacheStats {
+            total_entries: 100,
+            expired_entries: 10,
+            active_entries: 90,
+        };
+
+        let json = serde_json::to_string(&stats).unwrap();
+        assert!(json.contains("100"));
+        assert!(json.contains("10"));
+        assert!(json.contains("90"));
+
+        let deserialized: CacheStats = serde_json::from_str(&json).unwrap();
+        assert_eq!(deserialized.total_entries, 100);
+    }
+
+    #[tokio::test]
+    async fn test_ttl_cache_concurrent_access() {
+        let cache = Arc::new(TTLCache::new(Duration::from_secs(3600)));
+        let cache_clone = cache.clone();
+
+        let handle = tokio::spawn(async move {
+            for i in 0..10 {
+                cache_clone.insert(i, i * 2).await;
+            }
+        });
+
+        handle.await.unwrap();
+
+        for i in 0..10 {
+            assert_eq!(cache.get(&i).await, Some(i * 2));
+        }
+    }
+
+    #[tokio::test]
+    async fn test_llm_cache_full_workflow() {
+        let cache = create_llm_cache();
+        let key = LLMCacheKey::new("Hello, world!", "claude-3-sonnet", Some(0.7));
+
+        // Miss
+        assert!(cache.get(&key).await.is_none());
+
+        // Insert
+        cache.insert(key.clone(), "Response from LLM".to_string()).await;
+
+        // Hit
+        let cached = cache.get(&key).await;
+        assert_eq!(cached, Some("Response from LLM".to_string()));
+
+        // Different key misses
+        let different_key = LLMCacheKey::new("Different prompt", "claude-3-sonnet", Some(0.7));
+        assert!(cache.get(&different_key).await.is_none());
+    }
 }
diff --git a/crates/miyabi-core/src/error_policy.rs b/crates/miyabi-core/src/error_policy.rs
index 10831a5..7f47921 100644
--- a/crates/miyabi-core/src/error_policy.rs
+++ b/crates/miyabi-core/src/error_policy.rs
@@ -288,4 +288,249 @@ mod tests {
         breaker.reset().await;
         assert_eq!(breaker.state().await, CircuitState::Closed);
     }
+
+    #[test]
+    fn test_fallback_strategy_default() {
+        let strategy = FallbackStrategy::default();
+        match strategy {
+            FallbackStrategy::AcceptPartialSuccess { min_successful } => {
+                assert_eq!(min_successful, 1);
+            }
+            _ => panic!("Expected AcceptPartialSuccess"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_partial_success() {
+        let strategy = FallbackStrategy::partial_success();
+        match strategy {
+            FallbackStrategy::AcceptPartialSuccess { min_successful } => {
+                assert_eq!(min_successful, 1);
+            }
+            _ => panic!("Expected AcceptPartialSuccess"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_lower_temperature() {
+        let strategy = FallbackStrategy::lower_temperature();
+        match strategy {
+            FallbackStrategy::RetryWithLowerTemperature { temperature_reduction } => {
+                assert_eq!(temperature_reduction, 0.2);
+            }
+            _ => panic!("Expected RetryWithLowerTemperature"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_switch_model() {
+        let strategy = FallbackStrategy::switch_to_claude();
+        match strategy {
+            FallbackStrategy::SwitchModel { fallback_model } => {
+                assert_eq!(fallback_model, "claude-sonnet-4-5-20250929");
+            }
+            _ => panic!("Expected SwitchModel"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_wait_for_human() {
+        let strategy = FallbackStrategy::wait_for_human();
+        match strategy {
+            FallbackStrategy::WaitForHumanIntervention { timeout } => {
+                assert_eq!(timeout, Duration::from_secs(24 * 60 * 60));
+            }
+            _ => panic!("Expected WaitForHumanIntervention"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_skip_task() {
+        let strategy = FallbackStrategy::SkipTask;
+        assert!(matches!(strategy, FallbackStrategy::SkipTask));
+    }
+
+    #[test]
+    fn test_circuit_state_equality() {
+        assert_eq!(CircuitState::Closed, CircuitState::Closed);
+        assert_eq!(CircuitState::Open, CircuitState::Open);
+        assert_eq!(CircuitState::HalfOpen, CircuitState::HalfOpen);
+        assert_ne!(CircuitState::Closed, CircuitState::Open);
+        assert_ne!(CircuitState::Open, CircuitState::HalfOpen);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_default() {
+        let breaker = CircuitBreaker::default();
+        assert_eq!(breaker.state().await, CircuitState::Closed);
+        assert_eq!(breaker.failure_threshold, 5);
+        assert_eq!(breaker.success_threshold, 2);
+        assert_eq!(breaker.timeout, Duration::from_secs(60));
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_default_config() {
+        let breaker = CircuitBreaker::default_config();
+        assert_eq!(breaker.failure_threshold, 5);
+        assert_eq!(breaker.success_threshold, 2);
+        assert_eq!(breaker.timeout, Duration::from_secs(60));
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_success_closes_circuit() {
+        let breaker = CircuitBreaker::new(2, 2, Duration::from_millis(10));
+
+        // Open the circuit
+        for _ in 0..2 {
+            let _ = breaker
+                .call(|| {
+                    Box::pin(async {
+                        Result::<(), std::io::Error>::Err(std::io::Error::other("error"))
+                    })
+                })
+                .await;
+        }
+        assert_eq!(breaker.state().await, CircuitState::Open);
+
+        // Wait for timeout
+        tokio::time::sleep(Duration::from_millis(20)).await;
+
+        // First success puts it in half-open
+        let result = breaker
+            .call(|| Box::pin(async { Ok::<i32, std::io::Error>(42) }))
+            .await;
+        assert!(result.is_ok());
+
+        // Second success should close
+        let result = breaker
+            .call(|| Box::pin(async { Ok::<i32, std::io::Error>(42) }))
+            .await;
+        assert!(result.is_ok());
+
+        assert_eq!(breaker.state().await, CircuitState::Closed);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_consecutive_failures() {
+        let breaker = CircuitBreaker::new(3, 2, Duration::from_secs(60));
+
+        // Record one failure
+        let _ = breaker
+            .call(|| {
+                Box::pin(async {
+                    Result::<(), std::io::Error>::Err(std::io::Error::other("error"))
+                })
+            })
+            .await;
+        assert_eq!(breaker.consecutive_failures().await, 1);
+
+        // Record success - should reset failures
+        let _ = breaker
+            .call(|| Box::pin(async { Ok::<(), std::io::Error>(()) }))
+            .await;
+        assert_eq!(breaker.consecutive_failures().await, 0);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_consecutive_successes() {
+        let breaker = CircuitBreaker::new(3, 2, Duration::from_secs(60));
+
+        let _ = breaker
+            .call(|| Box::pin(async { Ok::<(), std::io::Error>(()) }))
+            .await;
+        assert_eq!(breaker.consecutive_successes().await, 1);
+
+        let _ = breaker
+            .call(|| Box::pin(async { Ok::<(), std::io::Error>(()) }))
+            .await;
+        // After reaching success_threshold, successes is reset
+        assert_eq!(breaker.consecutive_successes().await, 0);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_passes_result_through() {
+        let breaker = CircuitBreaker::new(3, 2, Duration::from_secs(60));
+
+        let result = breaker
+            .call(|| Box::pin(async { Ok::<i32, std::io::Error>(42) }))
+            .await;
+
+        assert_eq!(result.unwrap(), 42);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_custom_thresholds() {
+        let breaker = CircuitBreaker::new(1, 1, Duration::from_millis(10));
+
+        // Single failure opens circuit
+        let _ = breaker
+            .call(|| {
+                Box::pin(async {
+                    Result::<(), std::io::Error>::Err(std::io::Error::other("error"))
+                })
+            })
+            .await;
+        assert_eq!(breaker.state().await, CircuitState::Open);
+    }
+
+    #[tokio::test]
+    async fn test_circuit_breaker_reset_clears_counters() {
+        let breaker = CircuitBreaker::new(3, 3, Duration::from_secs(60));
+
+        // Record some failures
+        for _ in 0..2 {
+            let _ = breaker
+                .call(|| {
+                    Box::pin(async {
+                        Result::<(), std::io::Error>::Err(std::io::Error::other("error"))
+                    })
+                })
+                .await;
+        }
+
+        assert_eq!(breaker.consecutive_failures().await, 2);
+
+        breaker.reset().await;
+
+        assert_eq!(breaker.consecutive_failures().await, 0);
+        assert_eq!(breaker.consecutive_successes().await, 0);
+        assert_eq!(breaker.state().await, CircuitState::Closed);
+    }
+
+    #[test]
+    fn test_fallback_strategy_custom_partial_success() {
+        let strategy = FallbackStrategy::AcceptPartialSuccess { min_successful: 5 };
+        match strategy {
+            FallbackStrategy::AcceptPartialSuccess { min_successful } => {
+                assert_eq!(min_successful, 5);
+            }
+            _ => panic!("Expected AcceptPartialSuccess"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_custom_model() {
+        let strategy = FallbackStrategy::SwitchModel {
+            fallback_model: "gpt-4".to_string(),
+        };
+        match strategy {
+            FallbackStrategy::SwitchModel { fallback_model } => {
+                assert_eq!(fallback_model, "gpt-4");
+            }
+            _ => panic!("Expected SwitchModel"),
+        }
+    }
+
+    #[test]
+    fn test_fallback_strategy_custom_timeout() {
+        let strategy = FallbackStrategy::WaitForHumanIntervention {
+            timeout: Duration::from_secs(3600),
+        };
+        match strategy {
+            FallbackStrategy::WaitForHumanIntervention { timeout } => {
+                assert_eq!(timeout, Duration::from_secs(3600));
+            }
+            _ => panic!("Expected WaitForHumanIntervention"),
+        }
+    }
 }