Unit Test Bean Validation

Solid patterns for testing Jakarta Bean Validation constraints without spinning up Spring context. Covers the basics like @NotNull, @Email, @Min/@Max plus custom validators and cross-field validation. The setup is straightforward: build a Validator in @BeforeEach and assert against constraint violations. What I like here is the emphasis on testing both property paths and messages, not just violation counts. It includes parameterized test patterns and validation groups for conditional rules. The "most constraints ignore null by default" reminder in the pitfalls section will save you debugging time. Good for anyone writing DTOs with validation who wants fast unit tests instead of integration tests.