java-testing-advanced

Advanced testing techniques for comprehensive test coverage.

Overview

This skill covers advanced testing patterns including Testcontainers for integration testing, contract testing with Pact, mutation testing with PIT, and property-based testing.

When to Use This Skill

Use when you need to:

• Test with real databases (Testcontainers)
• Verify API contracts
• Find gaps with mutation testing
• Generate test cases automatically

Quick Reference

Testcontainers

@Testcontainers
@SpringBootTest
class OrderRepositoryIT {

    @Container
    static PostgreSQLContainer<?> postgres =
        new PostgreSQLContainer<>("postgres:15")
            .withDatabaseName("test")
            .withUsername("test")
            .withPassword("test");

    @Container
    static KafkaContainer kafka =
        new KafkaContainer(DockerImageName.parse("confluentinc/cp-kafka:7.4.0"));

    @DynamicPropertySource
    static void configure(DynamicPropertyRegistry registry) {
        registry.add("spring.datasource.url", postgres::getJdbcUrl);
        registry.add("spring.kafka.bootstrap-servers", kafka::getBootstrapServers);
    }

    @Test
    void shouldPersistOrder() {
        Order saved = repository.save(new Order("item", 100.0));
        assertThat(saved.getId()).isNotNull();
    }
}

Contract Testing (Pact)

@ExtendWith(PactConsumerTestExt.class)
class UserServiceContractTest {

    @Pact(consumer = "order-service", provider = "user-service")
    public RequestResponsePact createPact(PactDslWithProvider builder) {
        return builder
            .given("user exists")
            .uponReceiving("get user request")
                .path("/users/1")
                .method("GET")
            .willRespondWith()
                .status(200)
                .body(new PactDslJsonBody()
                    .integerType("id", 1)
                    .stringType("name", "John"))
            .toPact();
    }

    @Test
    @PactTestFor(pactMethod = "createPact")
    void testGetUser(MockServer mockServer) {
        User user = client.getUser(mockServer.getUrl(), 1L);
        assertThat(user.getName()).isEqualTo("John");
    }
}

Mutation Testing (PIT)

<plugin>
    <groupId>org.pitest</groupId>
    <artifactId>pitest-maven</artifactId>
    <version>1.15.0</version>
    <configuration>
        <targetClasses>
            <param>com.example.service.*</param>
        </targetClasses>
        <mutationThreshold>80</mutationThreshold>
    </configuration>
</plugin>

Property-Based Testing

@Property
void shouldReverseListTwiceReturnsOriginal(@ForAll List<Integer> list) {
    Collections.reverse(list);
    Collections.reverse(list);
    // Original order restored
}

Testing Pyramid

     /\        E2E Tests (few)
    /  \       Contract Tests
   /----\      Integration Tests
  /------\     Unit Tests (many)

Troubleshooting

| Problem | Solution | |---------|----------| | Container slow | Reuse containers | | Port conflicts | Random ports | | Flaky tests | Wait strategies |

Usage

Skill("java-testing-advanced")