In-memory database testing in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an in-memory database in testing?

An in-memory database stores data in the computer's RAM instead of on disk. It is fast and used in tests to simulate real databases without slow disk access.

beginner

Why use in-memory databases for unit tests?

They make tests faster and isolated by avoiding real database setup. This helps tests run quickly and reliably without external dependencies.

beginner

Name a popular in-memory database used in Java JUnit tests.

H2 database is popular for Java JUnit tests because it supports SQL and runs fully in memory.

intermediate

How do you ensure data isolation between tests using an in-memory database?

By resetting or recreating the in-memory database before each test, so tests do not share data and remain independent.

beginner

What is a common JUnit annotation to run setup code before each test?

The @BeforeEach annotation runs setup code before every test method to prepare the test environment.

What is the main advantage of using an in-memory database in tests?

A Faster test execution

B More disk space usage

C Slower queries

D Requires network connection

In-memory databases store data in RAM, making queries much faster and speeding up tests.

Which Java in-memory database is commonly used with JUnit?

A PostgreSQL

B MySQL

C Oracle

D H2

H2 is a lightweight in-memory database often used in Java tests.

How can you ensure tests do not affect each other when using an in-memory database?

A Reset the database before each test

B Run tests in parallel

C Use the same database instance for all tests

D Ignore test failures

Resetting the database before each test keeps tests independent and data isolated.

Which JUnit annotation is used to run code before each test method?

A @Test

B @BeforeEach

C @AfterEach

D @BeforeAll

@BeforeEach runs setup code before every test method.

In-memory databases are best suited for which type of testing?

A Load testing

B Production deployment

C Unit testing

D Manual testing

In-memory databases are ideal for unit tests because they are fast and isolated.

Explain how to set up an in-memory database for JUnit tests and why it is useful.

Think about test speed and independence.

Describe how in-memory database testing helps maintain test isolation and reliability.

Focus on data isolation and test independence.