Unit Testing Jakarta Bean Validation

Unit Testing Jakarta Bean Validation

Overview

This skill provides executable patterns for unit testing Jakarta Bean Validation annotations and custom validators using JUnit 5. Covers built-in constraints (@NotNull, @Email, @Min, @Max, @Size), custom @Constraint implementations, cross-field validation, and validation groups. Tests run in isolation without Spring context.

When to Use

• Writing unit tests for Jakarta Bean Validation or JSR-380 constraints
• Testing custom @Constraint validators and constraint violation messages
• Testing bean validation logic in DTOs and request objects
• Verifying cross-field validation (e.g., password matching)
• Testing conditional validation with validation groups
• Fast validation tests without Spring Boot context

Instructions

1. Add dependencies: Include jakarta.validation-api and hibernate-validator in test scope
2. Create base test class: Build Validator once in @BeforeEach using Validation.buildDefaultValidatorFactory()
3. Test valid cases first: Verify objects pass without violations
4. Test invalid cases: Assert constraint violations include correct property path and message
5. Extract violation details: Use getPropertyPath(), getMessage(), getInvalidValue()
6. Test custom validators: See references/custom-validators.md for patterns
7. Use parameterized tests: Test multiple inputs efficiently with @ParameterizedTest
8. Group validation tests: Use validation groups for conditional rules (see references/advanced-patterns.md)

Examples

Maven Setup

<dependency>
  <groupId>jakarta.validation</groupId>
  <artifactId>jakarta.validation-api</artifactId>
</dependency>
<dependency>
  <groupId>org.hibernate.validator</groupId>
  <artifactId>hibernate-validator</artifactId>
  <scope>test</scope>
</dependency>