unit-test-json-serialization

SKILL.md

Unit testing JSON serialization and deserialization with Spring's @JsonTest and Jackson.

Covers serialization/deserialization of POJOs, custom serializers/deserializers, field name mappings with @JsonProperty, and null handling using JacksonTester for type-safe assertions

Includes patterns for testing nested objects, lists, date/time formatting, and polymorphic types with @JsonTypeInfo

Provides Maven and Gradle setup, best practices for avoiding circular references and null inclusion issues, and troubleshooting guidance for common Jackson configuration problems

Uses @JsonTest annotation for lightweight JSON-focused test context without full Spring application startup

Unit Testing JSON Serialization with @JsonTest

Overview

Provides patterns for unit testing JSON serialization and deserialization using Spring's @JsonTest and Jackson. Covers POJO mapping, custom serializers, field name mappings, nested objects, date/time formatting, and polymorphic types.

When to Use

Testing JSON serialization/deserialization of DTOs

Verifying custom Jackson serializers/deserializers

Validating @JsonProperty, @JsonIgnore, and field name mappings

Testing date/time format handling (LocalDateTime, Date)

Testing null handling and missing fields

Testing polymorphic type deserialization

Instructions