Creating multiple databases before test execution (Junit, SpringBoot)

gistfile1.txt

Sometimes there is a need to create multiple databases prior to running integration tests (in a typical Spring/Spring Boot project). We can achieve this using a BeforeClass method in a JUnit test suite. Attached in this gist is the JUnit test suite and a persistence.xml file.

persistence.xml

<persistence xmlns="http://java.sun.com/xml/ns/persistence"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_3_0.xsd"
  version="2.0">
  <persistence-unit name="tenant" transaction-type="RESOURCE_LOCAL">
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
    <class>com.example.demoapp.entities.Tenant</class>

    <properties>
      <property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
      <property name="hibernate.dialect" value="org.hibernate.dialect.H2Dialect"/>
      <property name="hibernate.hbm2ddl.auto" value="create"/>
      <property name="packagesToScan" value="com.example.demoapp.entities"/>
    </properties>
  </persistence-unit>
</persistence>

SampleTestSuite.java

package com.example;

import java.nio.file.Paths;
import java.sql.SQLException;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Stream;
import org.h2.tools.Server;
import org.hibernate.jpa.HibernatePersistenceProvider;
import org.junit.BeforeClass;
import org.junit.runner.RunWith;
import org.junit.runners.Suite;
import org.junit.runners.Suite.SuiteClasses;

/**
 *
 */
@RunWith(Suite.class)
@SuiteClasses({TenantTest.class, AnotherTenantTest.class})
public class SampleTestSuite {

  public static final int NO_OF_TENANTS = 10;

  /**
   * Create multiple databases before running the applications and tests
   */
  @BeforeClass
  public static void createDatabases() throws InterruptedException, SQLException {

    //delete all the existing databases (this can also be done in a method with @AfterClass)
    //this is not necessary when running in-memory database
    Stream.of(Paths.get(System.getenv("USERPROFILE")).toFile().list((dir, fileName) -> {
      if (fileName != null && fileName.startsWith("tenant") && fileName.endsWith(".db")) {
        return true;
      }
      return false;
    })).forEach(file -> {
      boolean result = Paths.get(System.getenv("USERPROFILE"), file).toFile().delete();
      System.out.println("file - " + file + (result ? " deleted" : " not deleted"));
    });

    Server server = Server.createTcpServer("-tcpPort", "9123", "-tcpAllowOthers").start();

    while (!server.isRunning(true)) {

    }

    HibernatePersistenceProvider provider = new HibernatePersistenceProvider();
    Map<String, String> props = new HashMap<>();

    for (int i = 0; i < NO_OF_TENANTS; i++) {

      System.out.println("Configuring database for ... Tenant-" + i);

      props.put("javax.persistence.jdbc.url", "jdbc:h2:tcp://localhost:9123/~/tenant" + i);
      //props.put("javax.persistence.jdbc.username", "sa");
      //props.put("javax.persistence.jdbc.password", "sa");

      //some tenants can have default data
      if (i == 0) {
        props.put("javax.persistence.sql-load-script-source", "META-INF/tenant0_data.sql");
      } else if (i == 5) {
        props.put("javax.persistence.sql-load-script-source", "META-INF/tenant5_data.sql");
      } else {
        props.remove("javax.persistence.sql-load-script-source");
      }

      //this will generate all the tables from defined models
      provider.generateSchema("tenant", props);
    }


  }

}