Overview

DbUnitExtension is a JUnit 5/6 (Jupiter) extension that drives the IDatabaseTester setup/teardown lifecycle automatically, so a test class doesn’t need its own @BeforeEach/@AfterEach pair calling onSetup()/onTearDown().

Register it with @ExtendWith(DbUnitExtension.class). The test class still holds its own IDatabaseTester field — this is the same composition style as the IDatabaseTester guide, just with the lifecycle calls automated instead of written by hand:

@ExtendWith(DbUnitExtension.class)
class AccountRepositoryTest
{
    IDatabaseTester databaseTester =
            new JdbcDatabaseTester("org.h2.Driver", "jdbc:h2:mem:example;DB_CLOSE_DELAY=-1");

    @BeforeEach
    void loadDataset() throws Exception
    {
        databaseTester.setDataSet(new FlatXmlDataSetBuilder().build(new File("prep.xml")));
        databaseTester.setTearDownOperation(DatabaseOperation.DELETE_ALL);
    }

    @Test
    void testWithdraw_sufficientBalance_decrementsBalance() { ... }
}

@BeforeEach methods still run first — configure the dataset and any operation overrides there. The extension then calls onSetup() immediately before the test method and onTearDown() immediately after it, even if the test method fails or onSetup() itself throws.

Field Discovery

The extension finds the IDatabaseTester by scanning the test instance’s fields, including inherited ones:

• The nearest declaring class wins — a field on the test class itself takes precedence over one on a superclass.
• That class must declare exactly one non-static field assignable to IDatabaseTester. No match anywhere in the hierarchy, or two-or-more matches at the same class level, both fail fast with a descriptive IllegalStateException rather than guessing.
• Static fields are ignored.
• Private fields are found; the field’s own access modifier doesn’t matter.

When to Use This Instead of Manual Lifecycle Calls

Reach for DbUnitExtension when a @BeforeEach/@AfterEach pair that only calls onSetup()/onTearDown() (as shown in the IDatabaseTester guide) would just be boilerplate repeated across every test class. Write the @BeforeEach/@AfterEach pair yourself instead when a test needs other logic around those calls, or targets a JUnit version this extension doesn’t support.