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name: spring-boot-testing description: Write unit, integration, and slice tests for Spring Boot 3 applications. Use when writing unit tests, integration tests, or slice tests for Spring Boot 3 applications. metadata: triggers: files: - '**/*Test.java' keywords: - webmvctest - datajpatest - testcontainers - assertj

Spring Boot Testing Standards

Priority: P0 (CRITICAL)

Core Rule Anchors

• [BE-TEST-01] Parameterized Tests for Equivalent Cases: Prefer @ParameterizedTest (@CsvSource, @MethodSource) when methods have multiple equivalent inputs or boundary permutations. Distinct scenarios may stay separate test methods. Reviewers must not demand parameterized rewrites without a behavioral gap.
• [BE-TEST-02] Ban on Brittle DB Mock String Matching: Do not use string-matching mocks for raw SQL queries. Test pure domain calculations directly, or use Testcontainers for database repository verification.
• [BE-TEST-03] Ban on Shallow Assertions: Never assert only assertThat(result).isNotNull() without inspecting domain fields, status codes, and invariants.
• [BE-TEST-04] Ban on Pass-Through Interface Mocks: Repositories and service handlers must test contract compliance and error mapping. Ban 1:1 pass-through mock echoing without contract assertions.
• [BE-TEST-05] Bug-First Regression Lock: Every PR fixing a bug ticket or with title fix(...) must introduce a test reproducing the defect prior to the fix.

Follow TDD Workflow

1. Red: Write failing test (e.g., returns 404) ([BE-TEST-05]).
2. Green: Implement minimal code to pass.
3. Refactor: Clean up while keeping tests green ([BE-TEST-01]).
4. Coverage: Diagnostic and project-configured; verify risk-weighted critical paths rather than padding code for an arbitrary percentage.

Write Slice and Integration Tests

• Real Infrastructure ([BE-TEST-02]): Use Testcontainers for DB/Queues. Avoid H2/Embedded.
• Assertions ([BE-TEST-03]): Use AssertJ (assertThat) over JUnit assertions; avoid shallow checks.
• Isolation ([BE-TEST-04]): Use @MockBean for downstream dependencies in Slice Tests; avoid pass-through mock echoing.

See implementation examples for WebMvcTest slice tests and Testcontainers integration tests.

Anti-Patterns

• [BE-TEST-01] Stylistic parameterized rewrites: Do not demand parameterized refactoring of passing tests without a behavioral gap.
• [BE-TEST-02] Brittle DB mock string matching: Do not match raw SQL strings in mocks; use Testcontainers.
• [BE-TEST-03] Shallow assertions: Never assert only assertThat(result).isNotNull() without inspecting domain fields or status codes.
• [BE-TEST-04] Pass-through mock echoing: Ban 1:1 pass-through mock echoing without contract assertions.
• [BE-TEST-05] Bug fix without reproduction test: Ban bug fixes without a regression test.
• No Dirty Contexts: Avoid @MockBean in base classes; it reloads context per test.
• No network I/O in tests: Mock external calls with WireMock.
• No System.out in tests: Use AssertJ assertions instead.

References

• Implementation Examples