Discussion: constructor parameter resolution, scope, etc. #1731
Description
Thanks for adding TempDirectory to JUnit 5.4.0-M1. This will make migration from JUnit 4 easier in my projects :-)
One point looks wrong to me though:
A @TempDir constructor parameter is treated like a parameter of a @BeforeAll method, ie its value is shared between all tests. See Javadoc of TempDirectory:
The temporary directory will be shared by all tests in a class when the annotation is present on a parameter of a @BeforeAll method or the test class constructor. Otherwise, e.g. when only used on test or @beforeeach or @AfterEach methods, each test will use its own temporary directory.
I would expect a @TempDir constructor parameter to be treated like parameter of a @BeforeEach method, ie a new value for each test.
I'm not sure about the finer points of parameter resolving in JUnit, so maybe the current behavior is as intended. Reasons why I think a @TempDir constructor parameter should have a new value for each test:
- According to the User Guide "JUnit creates a new instance of each test class before executing each test method"
New instance -> new constructor call -> new value for constructor parameter (my expectation) @BeforeAll= by default a static method = global state
@BeforeEach= instance method = single test state
constructor = instance bound = single test state- I normally want a clean temp directory for each test. Sometimes a shared temp directory might be needed, but it's the exception.
- Isn't
@TestInstance(Lifecycle.PER_CLASS)the normal way to share constructor state between all tests?
By the way, the Javadoc is really thorough. Very helpful!