Provides unit test, integration test, and mock AI patterns for LangChain4j applications. Creates mock LLM responses, tests retrieval chains, validates RAG workflows, and implements Testcontainers-based integration tests for Java AI services. Use when unit testing AI services, integration testing Lan

LangChain4J Testing Strategies Overview Patterns for unit testing with mocks, integration testing with Testcontainers, and end to end validation of RAG systems, AI Services, and tool execution. When to Use Unit testing AI services : When you need fast, isolated tests for services using LangChain4j AiServices Integration testing LangChain4j components : When testing real ChatModel, EmbeddingModel, or RAG pipelines with Testcontainers Mocking AI models : When you need deterministic responses without calling external APIs Testing LLM based Java applications : When validating RAG workflows, tool execution, or retrieval chains Instructions 1. Unit Testing with Mocks Use mock models for fast, isolated testing. See references/unit testing.md . 2. Configure Testing Dependencies Setup Maven/Gradle dependencies. See references/testing dependencies.md . langchain4j test Guardrail assertions testcontainers Containerized testing mockito Mock external dependencies assertj Fluent assertions 3. Integration Testing with Testcontainers Test with real services. See references/integration testing.md . 4. Advanced Features Streaming, memory, error handling patterns in references/advanced testing.md . 5. Testing Workflow Follow the testing pyramid from references/workflow patterns.md : 70% Unit Tests : Fast, isolated with mocks 20% Integration Tests : Real services with health checks 10% End to End Tests : Complete workflows Troubleshooting Container fails to start : Check Docker daemon is running, verify image exists, increase timeout Model not responding : Verify baseUrl is correct, check container logs, ensure model is loaded Test timeout : Increase @Timeout duration for slow models, check container resource limits Flaky tests : Add retry logic or health checks before assertions Examples Unit Test Integration Test with Testcontainers Best Practices Use @BeforeEach / @AfterEach for test isolation Never call real APIs in unit tests; use mocks Include @Timeout for external service calls Test both success and error handling scenarios Validate response coherence and edge cases Common Patterns Mock Strategy Assertion Helpers Reference Documentation [Testing Dependencies](references/testing dependencies.md) Maven/Gradle configuration [Unit Testing](references/unit testing.md) Mock models, guardrails [Integration Testing](references/integration testing.md) Testcontainers, real services [Advanced Testing](references/advanced testing.md) Streaming, memory, error handling [Workflow Patterns](references/workflow patterns.md) Test pyramid, best practices Constraints and Warnings AI responses are non deterministic; use mocks for reliable unit tests Avoid real API calls in tests to prevent costs and rate limiting Integration tests require Docker; use container health checks RAG tests need properly seeded embedding stores Mock based tests cannot guarantee actual LLM behavior; supplement with integration tests Use test specific configuration profiles; never affect production data

langchain4j-testing-strategies