Gen Ut

Generate Unit Tests

Inputs and Scope

Require target production classes, preferably as fully-qualified names. Accept an optional module and optional test-class execution filter. Discover related tests by the exact <TargetClassName>Test convention and update them in place; create that class only when none exists.

Resolve:

• <ResolvedTargetClasses>: requested production classes.
• <ResolvedTestFileSet>: only related test Java files and required test resources that may be edited.
• <ResolvedTestModules>: explicit Maven modules owning those tests.
• <ResolvedTestClass>: focused test-class filter for execution.

Use an explicitly supplied module first. Otherwise resolve the nearest owning pom.xml from test files, then target sources. If target classes or modules cannot be resolved, return R10-INPUT_BLOCKED.

Ownership Terms

• SUT-owned behavior: decisions, branches, state changes, calls, results, or error handling owned by the target class.
• Collaborator-owned behavior: behavior computed by an SPI, registry, factory, parser, loader, driver, dialect, metadata option, or another dependency.
• Testing through layers: driving or asserting collaborator-owned rules instead of mocking the result consumed by the target.
• KEEP:<id>:<reason>: evidence for retaining an otherwise redundant candidate because removal materially harms readability or diagnosis.
• Task scope baseline: structured pre-edit snapshot of the allowed test files and every dirty path outside them.

Mandatory Rules

MUST, SHOULD, and MAY are normative. This section is the source of R1-R15; workflow and command examples do not override it.

R1: Repository authority

Before any test write, read AGENTS.md and code-implementation/SKILL.md through EOF, then read every reference selected by that base Skill for this task through EOF, including its implementation, testing, contract, impact, removal, non-regression, and verification rules. Follow the applicable CODE_OF_CONDUCT.md sections. The base Skill owns universal implementation, testing, non-regression, verification, and completion requirements; this Skill adds target resolution, coverage, branch-map, parameterization, and scanner requirements for systematic unit-test generation. Reading either Skill does not expand the user-authorized scope, file types, Git authority, or other permissions.

R2: Test form and naming

• Use JUnit 5 @Test for standalone scenarios.
• Use @ParameterizedTest(name = "{0}"), @MethodSource, and Arguments for data-driven scenarios. Declare final String name first and provide at least three rows.
• Do not use @RepeatedTest, Consumer as scenario transport, switch dispatch inside parameterized tests, or new nested transport types.
• Follow repository test naming. A single test uniquely covering one public method is assert<MethodName>.

R3: Change boundary

• Edit only <ResolvedTestFileSet> under src/test/java or src/test/resources.
• Do not edit production, generated output, unrelated tests, or another file type.
• Capture Task scope baseline after resolving the file set and before editing. Any candidate-relevant changed path outside that set is a failure, including further mutation of a path already dirty at task start. Exclude only untracked or ignored reproducible verification outputs such as Maven target/ and Python __pycache__/; they are not editable scope and must not be modified intentionally.
• Obtain explicit approval before expanding scope. Never use destructive Git operations.

R4: Branch map

• Before coding, enumerate target public-method branches and map each planned scenario to one branch or path.
• Classify every trigger and assertion as SUT-owned or collaborator-owned. Isolate collaborator-owned results at the nearest stable boundary and apply R6 to decide whether to mock them.
• Exclude Lombok-generated behavior without custom logic. Default to one test per branch or path; use R13 for additional cases.

R5: Scenario granularity

• Keep one scenario per test and invoke the target public method once by default. Invoke it more than once only when repeated invocation is itself the scenario, such as idempotency, accumulation, or a state transition.
• Keep the coverage-relevant invocation and its externally observable assertions in the test body. Helpers and providers must not execute target behavior.
• For interface targets, test owned default or static methods directly. Exercise abstract contracts through concrete implementations, including when the user explicitly requests an interface-contract test.

R6: SPI, mocks, and reflection

• Exercise interface default methods with Mockito CALLS_REAL_METHODS.
• Obtain SPI targets through the applicable project loader and keep the resolved instance as a test-class field by default. Record a concrete reason before bypassing the loader.
• Do not add tests for getType, getOrder, or getTypeClass unless explicitly requested.
• Mock heavy dependencies and collaborator-owned decisions. Allow real simple values and explicitly scoped integration, contract, or E2E behavior.

R7: Related tests

Update existing related tests in place and fill missing coverage first. An explicit test-class input filters execution only; it does not replace related-test discovery. Create a new exact-name test class only when none exists.

R8: Parameterization analysis

For each target public method, record R8-CANDIDATES with the method, candidate count, decision, and evidence. A candidate is high-fit only when all are true:

1. target method and branch skeleton are consistent;
2. differences are mainly input data;
3. assertion skeleton is consistent or differences are explicitly declared;
4. at least three scenarios exist;
5. no switch dispatch is required.

Collaborator-owned differences are not high-fit. Refactor high-fit candidates; otherwise record the concrete reason. Use KEEP only when a genuinely high-fit refactor would materially reduce readability or diagnosis.

The scanner discovers possible groups but never decides semantic high-fit. Treat its candidate count as evidence to review, not an instruction to refactor.

R9: Coverage blockers

When unreachable production code blocks coverage, report the class, path, exact line, and reason. Do not change production code within this Skill.

R10: Completion state

Use exactly one state:

• R10-INPUT_BLOCKED: target classes or test modules cannot be resolved.
• R10-A: scope is clean; focused tests execute at least one test; declared target coverage is met for every target and inner class; repository formatting/checkstyle gates pass; both final rule scans pass; semantic reviews and R8 decisions are complete.
• R10-B: production dead code blocks the target and R9 evidence is complete.
• R10-C: an out-of-scope failure is evidenced under R11.
• R10-D: work remains; continue instead of claiming completion.

Priority is INPUT_BLOCKED > B > C > A > D. By default, cover the requested behavior and every affected SUT-owned branch. Apply a numeric CLASS, LINE, or BRANCH target only when the user states it; an explicit 100% target remains mandatory.