In my previous post on testing, I described how to use TestContainers to provide realistic test environments for database tests. This comment revealed the downside:

…as noted above, there always seems to be some drawback. In this case, the overhead of starting the Docker image and everything it contains will increase your overall build time.

As a reminder, here’s the TestContainer-specific code. Note the instance member postgres, and the JUnit Rule that re-initializes it on a per-method basis.

package be.objectify.tcexample.db;

import be.objectify.tcexample.AbstractUserDaoTest;
import be.objectify.tcexample.UserDao;
import org.junit.After;
import org.junit.Before;
import org.junit.Rule;
import org.testcontainers.containers.PostgreSQLContainer;
import play.db.Database;

public class JooqUserDaoTest extends AbstractUserDaoTest implements DbTestSupport,
 TestData {

 @Rule
 public PostgreSQLContainer postgres = new PostgreSQLContainer();
 
 private Database database;
 
 @Before
 public void setup() throws Exception {
 // the database has all evolutions applied
 database = create(postgres); 
 // load some test data
 loadTestData(database); 
 }

 @After
 public void tearDown() {
 destroy(database);
 }

 @Override
 public UserDao dao() {
 return new JooqUserDao(database);
 }
}

Given that the huge increase in test duration results from Docker container start-up times, we can instead use a JUnit ClassRule to start up one container and re-use it for every test in the class. This means you should no longer run these tests in parallel, but the performance gains massively outweigh test parallelization.

package be.objectify.tcexample.db;

import be.objectify.tcexample.AbstractUserDaoTest;
import be.objectify.tcexample.UserDao;
import org.junit.After;
import org.junit.Before;
import org.junit.ClassRule;
import org.testcontainers.containers.PostgreSQLContainer;
import play.db.Database;

public class FasterJooqUserDaoTest extends AbstractUserDaoTest implements DbTestSupport,
 TestData {

 @ClassRule
 public static PostgreSQLContainer postgres = new PostgreSQLContainer();
 
 private Database database;
 
 @Before
 public void setup() throws Exception {
 database = create(postgres); 
 loadTestData(database); 
 }

 @After
 public void tearDown() {
 destroy(database);
 }

 @Override
 public UserDao dao() {
 return new JooqUserDao(database);
 }
}

The amount of time saved depends on the number of test methods in a class. I have some test classes that have upwards of 30 tests each, and in these cases the execution time drops from minutes to seconds. Not bad for changing a couple of lines of code.