backend-spring-test

name	backend-spring-test
description	Use when reviewing Spring Boot test code — test slice selection (`@SpringBootTest` vs `@WebMvcTest` vs `@DataJpaTest`), `@MockBean` overuse, Testcontainers vs H2, `@DirtiesContext` hygiene, security context in tests. Triggers when Spring Boot test files are in scope.
spring_boot_versions	["3.x"]

Spring Test Review

Overview

Review Spring Boot tests for appropriate slice scope, mock placement, and context isolation. Pairs with the agnostic testing-strategy-review (which covers test pyramid, mocking SUT, flaky patterns).

Triggers when spring-boot-starter-test is detected and test source files are in scope. The agnostic skill flags WHAT is wrong with a test; this skill flags HOW Spring's test annotations should be used.

Version Compatibility

Supported: Spring Boot 3.x (declared via spring_boot_versions: ["3.x"] in frontmatter).

Spring Boot 2.x — degraded coverage:

• All checks (ST1–ST10) apply identically across SB2/SB3
• Package paths differ slightly (jakarta.servlet.* in SB3 vs javax.servlet.* in SB2 for MockMvc/WebMvcTest internals)

Spring Boot 3.4+: @MockBean was deprecated in Spring Framework 6.2 in favor of @MockitoBean / @MockitoSpyBean. ST2/ST3 examples in this skill use @MockBean; on SB3.4+ codebases prefer @MockitoBean. The semantic checks (mock necessity, slice scope) are unchanged.

To extend coverage for SB2 or SB3.4+, follow Pattern A (broaden the rubric) per shield/skills/backend/EXTENDING-VERSIONS.md.

When to Use

• Reviewing @SpringBootTest, @WebMvcTest, @DataJpaTest, etc.
• Reviewing @MockBean and @SpyBean usage
• Reviewing Testcontainers vs H2 in-memory choices
• Reviewing test security context (@WithMockUser, etc.)

When NOT to Use

• Pure JUnit assertion patterns — use testing-strategy-review
• Non-Spring test frameworks (pytest, jest) — different conventions
• Performance test design — separate skill not in v1

Review Process

1. Inventory: test classes by their primary slice annotation
2. For each, apply Evaluation Points ST1–ST10
3. Cross-cut: confirm @SpringBootTest is reserved for full integration, not unit tests in disguise

Evaluation Points

#	Check	What to Look For	Severity
ST1	Test slice selection	Use @WebMvcTest for controllers, @DataJpaTest for repos, @JsonTest for serialization, @SpringBootTest only when truly integration-shaped	High
ST2	@MockBean necessity	Mock collaborators that aren't part of the slice. Don't mock everything — slice annotations auto-configure the layer	Medium
ST3	@SpringBootTest scope	Full context boot is slow. Justify when a smaller slice would work	High
ST4	@DirtiesContext minimization	Recreating the context per test is very slow. Use only when absolutely required (rare); prefer test-data isolation via transactions or @Sql	High
ST5	Testcontainers vs H2	Testcontainers gives a real database (catches dialect issues). H2 is faster but masks production differences. Choose deliberately	Medium
ST6	Test security context	@WithMockUser, @WithUserDetails, or custom security context. Don't disable security in tests	Medium
ST7	@Transactional in tests	Tests marked @Transactional roll back automatically — good for isolation. Avoid in tests that span multiple transactions	Medium
ST8	MockMvc vs WebTestClient	MockMvc for MVC; WebTestClient for WebFlux. Don't mix layers	Low
ST9	Parallel test safety	If tests run in parallel, no shared mutable state across classes. @Execution(SAME_THREAD) for legacy tests	Medium
ST10	Test data setup	@Sql for repo tests, TestEntityManager.persist in @DataJpaTest. Don't rely on schema state from prior tests	Medium

Critical Checks

• @SpringBootTest on a test that exercises one controller (slice annotation would be faster)
• @DirtiesContext(classMode = BEFORE_EACH_TEST_METHOD) (extremely slow)
• A test class with 5+ @MockBeans (smell — the slice is wrong)
• A test that asserts on database state without resetting between methods

Severity Guide

Severity	When
High	CI slowness or false confidence (heavy slice for unit-shaped test, no assertions, dirties-context per method)
Medium	Friction during normal feature work (wrong mock placement, missing isolation)
Low	Style — slice consistency, minor naming

Common Mistakes

Mistake	Fix
Demanding @WebMvcTest for every controller test	Some controllers genuinely need the full context (e.g., to verify security filters interact). The smell is when @WebMvcTest would clearly suffice
Flagging all @MockBean usage	@MockBean is the right tool for external dependencies. The smell is mocking domain services already in the slice
Insisting on Testcontainers always	H2 is fine for repo tests that don't exercise dialect-specific SQL. Testcontainers is required when SQL features differ
Treating @Transactional tests as anti-pattern	Tx-rollback tests give clean isolation. The smell is using them when the test must span transactions (e.g., testing a saga)
Demanding security context in every test	Pure unit tests don't need it. The smell is integration tests bypassing security to "make tests pass"

Related Skills

• For test pyramid balance, mock SUT, flaky patterns → backend-testing-strategy-review
• For JPA repository test patterns → backend-spring-data (P5–P8)
• For controller test patterns alongside @WebMvcTest → backend-spring-web (W4)