Introduce support for class-scoped parameters

[kcooney]

Overview

Provide a way to have values injected into a class that are created once before any test methods are created.

If your test class has constructor with a parameter annotated with @PerClass, then JUnit Jupiter will create it once per run of the test class, using the default constructor of the class (in Kotlin, the primary constructor). That class can have non-static methods annotated with @BeforeAll, @AfterAll, @BeforeEach, or @AfterEach.

Here's an example of a class that creates a local database:

    @PerClass
    public class Database {
        @BeforeAll void createDatabase() {
        }
 
        @AfterAll void dropDatabase() {
        }

        @BeforeEach void clearDatabase() {
        }

        public void insert(long id, Account) }{
       }
    }

    class DatabaseTestCase {
      private final Database db;

      DatabaseTestCase(@PerClass Database db) {
        this.db = db;
      }

      @Test
      public void insertAccount() {
        Account account = ...
        db.insert(1, account);
        ...
      }
    }

You could think of this as a better version of JUnit4's ExternalResource rule.

This could also be used to support @BeforeAll in Kotlin tests

    class SimpleKotlinTestCase constructor(@PerClass db: Database) {
      class Database {
        @BeforeAll fun createDatabase() {
        }
 
        @AfterAll fun dropDatabase() {
        }

        @BeforeEach fun clearDatabase() {
        }

        fun insert(id: Int, account: Account) {
        }
      }

      @Test
      fun insertAccount() {
        val account = ...
        db.insert(1, account);
        ...
      }
    }

This could also be used to support integration tests.

Deliverables

• ?

[sbrannen]

Updated title and description.

[sbrannen]

FYI: developers and third parties can already achieve comparable functionality via a custom extension that implements BeforeAllCallback, AfterAllCallback, BeforeEachCallback, AfterEachCallback, and ParameterResolver.

With that in mind, I'm not convinced that JUnit Jupiter should implement such a feature itself.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Given the limited bandwidth of the team, it will be automatically closed if no further activity occurs. Thank you for your contribution.

[stale]

This issue has been automatically closed due to inactivity. If you have a good use case for this feature, please feel free to reopen the issue.