You can obtain a temporary database in one of two ways:

Database containers launched via JDBC URL scheme

As long as you have Testcontainers and the appropriate JDBC driver on your classpath, you can simply modify regular JDBC connection URLs to get a fresh containerized instance of the database each time your application starts up.

Original URL : jdbc:mysql://localhost:3306/databasename

Insert tc: after jdbc: as follows. Note that the hostname, port and database name will be ignored; you can leave these as-is or set them to any value.

We will use /// (host-less URIs) from now on to emphasis the unimportance of the host:port pair.
From Testcontainers' perspective, jdbc:mysql:8.0.36://localhost:3306/databasename and jdbc:mysql:8.0.36:///databasename is the same URI.

Warning

If you're using the JDBC URL support, there is no need to instantiate an instance of the container - Testcontainers will do it automagically.

JDBC URL examples

Using ClickHouse

jdbc:tc:clickhouse:18.10.3:///databasename

Using CockroachDB

jdbc:tc:cockroach:v21.2.3:///databasename

Using CrateDB

jdbc:tc:cratedb:5.2.3:///databasename

Using DB2

jdbc:tc:db2:11.5.0.0a:///databasename

Using MariaDB

jdbc:tc:mariadb:10.3.39:///databasename

Using MySQL

jdbc:tc:mysql:8.0.36:///databasename

Using MSSQL Server

jdbc:tc:sqlserver:2017-CU12:///databasename

Using OceanBase

jdbc:tc:oceanbasece:4.2.1-lts:///databasename

Using Oracle

jdbc:tc:oracle:21-slim-faststart:///databasename

Using PostGIS

jdbc:tc:postgis:9.6-2.5:///databasename

Using PostgreSQL

jdbc:tc:postgresql:9.6.8:///databasename

Using QuestDB

jdbc:tc:questdb:6.5.3:///databasename

Using TimescaleDB

jdbc:tc:timescaledb:2.1.0-pg13:///databasename

Using PGVector

jdbc:tc:pgvector:pg16:///databasename

Using TiDB

jdbc:tc:tidb:v6.1.0:///databasename

Using Timeplus

jdbc:tc:timeplus:2.3.21:///databasename

Using Trino

jdbc:tc:trino:352://localhost/memory/default

Using YugabyteDB

jdbc:tc:yugabyte:2.14.4.0-b26:///databasename

Using a classpath init script

Testcontainers can run an init script after the database container is started, but before your code is given a connection to it. The script must be on the classpath, and is referenced as follows:

jdbc:tc:mysql:8.0.36:///databasename?TC_INITSCRIPT=somepath/init_mysql.sql

This is useful if you have a fixed script for setting up database schema, etc.

Using an init script from a file

If the init script path is prefixed file: , it will be loaded from a file (relative to the working directory, which will usually be the project root).

jdbc:tc:mysql:8.0.36:///databasename?TC_INITSCRIPT=file:src/main/resources/init_mysql.sql

Using an init function

Instead of running a fixed script for DB setup, it may be useful to call a Java function that you define. This is intended to allow you to trigger database schema migration tools. To do this, add TC_INITFUNCTION to the URL as follows, passing a full path to the class name and method:

jdbc:tc:mysql:8.0.36:///databasename?TC_INITFUNCTION=org.testcontainers.jdbc.JDBCDriverTest::sampleInitFunction

The init function must be a public static method which takes a java.sql.Connection as its only parameter, e.g.

public class JDBCDriverTest {
    public static void sampleInitFunction(Connection connection) throws SQLException {
        // e.g. run schema setup or Flyway/liquibase/etc DB migrations here...
Running container in daemon mode
By default database container is being stopped as soon as last connection is closed. There are cases when you might need to start container and keep it running till you stop it explicitly or JVM is shutdown. To do this, add TC_DAEMON parameter to the URL as follows:
jdbc:tc:mysql:8.0.36:///databasename?TC_DAEMON=true
With this parameter database container will keep running even when there's no open connections.
Running container with tmpfs options
Container can have tmpfs mounts for storing data in host memory. This is useful if you want to speed up your database tests. Be aware that the data will be lost when the container stops.
To pass this option to the container, add TC_TMPFS parameter to the URL as follows:
jdbc:tc:postgresql:9.6.8:///databasename?TC_TMPFS=/testtmpfs:rw
If you need more than one option, separate them by comma (e.g. TC_TMPFS=key:value,key1:value1&other_parameters=foo).
For more information about tmpfs mount, see the official Docker documentation.
Database container objects
In case you can't use the URL support, or need to fine-tune the container, you can instantiate it yourself.
Add a @Rule or @ClassRule to your test class, e.g.:
public class SimpleMySQLTest {
    @Rule
    public MySQLContainer mysql = new MySQLContainer();
Now, in your test code (or a suitable setup method), you can obtain details necessary to connect to this database:
mysql.getJdbcUrl() provides a JDBC URL your code can connect to
mysql.getUsername() provides the username your code should pass to the driver
mysql.getPassword() provides the password your code should pass to the driver
Note that if you use @Rule, you will be given an isolated container for each test method. If you use @ClassRule, you will get on isolated container for all the methods in the test class.
Examples/Tests:
MySQL
PostgreSQL