test

Instruction file imported from ArulaAI/copilot-engineering-test-optimization-lab-java (.github/instructions/test.instructions.md). Copyright stays with the author.

Naming

• Method format: should[ExpectedBehavior]When[Condition] — shouldThrowWhenAmountIsNegative
• @ParameterizedTest must include name = "..." with a readable sentence using {0}, {1} placeholders

Assertions

• Use AssertJ (assertThat()) exclusively — never JUnit's assertEquals() or assertTrue()
• For exceptions: assertThatThrownBy(() -> ...) — never try/catch with fail()
• Assert on exception message and error code, not just exception type
• One assertion cluster per test — split if two unrelated things are asserted

Mocking

• BDD Mockito only: given(...).willReturn(...) setup, then(...).should(...) verify — never mix with when/verify
• Stub only what the test actually calls
• Verify only interactions that are the intent of the test — not incidental calls

Test Data

• Named constants for all boundary values — no magic numbers
• Use @EnumSource for exhaustive enum coverage, @CsvSource for input/output pairs, @MethodSource for complex object scenarios

Time and Async

• Never call LocalDate.now() or LocalDateTime.now() directly — inject Clock and mock it
• Never use Thread.sleep() or Math.random() in tests
• Use CompletableFuture.join() with an explicit timeout — never .get() without one

Spring Context

• Service-layer tests use @ExtendWith(MockitoExtension.class) — never @SpringBootTest