Can Mocktio mock a persistence provider, so that jenkins (or other pipeline tools) can execute JUnit tests without a database?

So I wrote JUnit tests, including Mockito, for an API that directly uses DAOs. The mocking of the EntityManager and EntityTransaction is no problem and the tests are running fine on a machine, where the persistence provider can connect to the database. (EclipseLink is used)

Jenkins however, which is also running these tests, has no access to the database in question. Everytime Jenkins executes the tests I get:

No Persistence provider for EntityManager named XYZ

I do understand that this occurs due to the fact that jenkins can not establish a real connection to the database. This behavior is intentional and should not change.

My question therefore is: is it possible to mock (with Mockito?), or in antoher way fake, the connection so that a fake EntityManagerFactory / persistence provider can be used?

Solution

A way to test the closed API without a real database access is to build and fill & tear-down an in-memory database for tests. A simple setup with Spring & Derby for Eclipselink would be

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.transaction.TransactionConfiguration;
import javax.persistence.EntityManagerFactory;
import javax.persistence.PersistenceUnit;

@ContextConfiguration(classes = AppConfig.class)
@TransactionConfiguration(defaultRollback = false)
public abstract class AbstractContainer {

@PersistenceUnit(unitName = "PERSISTENT_UNIT_NAME")
protected EntityManagerFactory factory;

@Autowired
protected ApplicationContext applicationContext;

}

and

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.jdbc.datasource.DriverManagerDataSource;
import org.springframework.orm.jpa.JpaVendorAdapter;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter;
import java.util.Properties;
import javax.sql.DataSource;

@Configuration
public class AppConfig {

@Bean
public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
LocalContainerEntityManagerFactoryBean em =
    new LocalContainerEntityManagerFactoryBean();
em.setDataSource(dataSource());
em.setPersistenceUnitName("PERSISTENT_UNIT_NAME");
em.setPackagesToScan(new String[] { "package.name.to.scan" });

JpaVendorAdapter vendorAdapter = new EclipseLinkJpaVendorAdapter();

em.setJpaVendorAdapter(vendorAdapter);
// here some additional properties for the PU
em.setJpaProperties(additionalProperties());

return em;
}

Properties additionalProperties() {
Properties properties = new Properties();

properties.setProperty("eclipselink.weaving", "false");
properties.setProperty("eclipselink.query-results-cache", "false");
properties.setProperty("eclipselink.cache.shared.default", "false");

properties.setProperty("javax.persistence.jdbc.driver",
    "org.apache.derby.jdbc.EmbeddedDriver");
properties.setProperty("javax.persistence.jdbc.url",
    "jdbc:derby:memory:NAME;create=true");

properties.setProperty("javax.persistence.jdbc.url", "jdbc:derby:PATH");
properties.setProperty("javax.persistence.jdbc.user", "");
properties.setProperty("javax.persistence.jdbc.password", "");

properties.setProperty("javax.persistence.sql-load-script-source",
    "META-INF/sql/createDB.sql");
properties.setProperty("eclipselink.deploy-on-startup", "true");
properties.setProperty("eclipselink.target-database", "Derby");

return properties;
}

public DataSource dataSource() {
DriverManagerDataSource dataSource = new DriverManagerDataSource();
try {
  Class.forName("org.eclipse.persistence.jpa.PersistenceProvider");
  Class.forName("org.apache.derby.jdbc.EmbeddedDriver").newInstance();
} catch (ClassNotFoundException cnfe) {
  cnfe.printStackTrace();
} catch (InstantiationException inste) {
  inste.printStackTrace();
} catch (IllegalAccessException iace) {
  iace.printStackTrace();
}

dataSource.setDriverClassName("org.apache.derby.jdbc.EmbeddedDriver");
dataSource.setUrl("jdbc:derby:memory:NAME;create=true");

dataSource.setUsername("");
dataSource.setPassword("");

return dataSource;
}

}

The SQL Script lies under test/resources/META-INF/sql/createDB.sql.
Finally your Test Class extends the Abstract Container using the SpringJUnit4ClassRunner.class Runner and starts a local transaction.

@RunWith(SpringJUnit4ClassRunner.class)
public class DAOTest extends AbstractContainer {

@Test
public void testDAO() {

EntityManager em = factory.createEntityManager();
em.getTransaction().begin();
}
}

The persistence unit for tests is per default expected under test/resources/META-INF/.

Dependencies using Maven

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>[4.1.7.RELEASE]</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-orm</artifactId>
        <version>[4.1.7.RELEASE]</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>[4.1.7.RELEASE]</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-mock</artifactId>
        <version>[2.0.8]</version>
        <scope>test</scope>
    </dependency>   
    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derby</artifactId>
        <version>10.11.1.1</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.apache.derby</groupId>
        <artifactId>derby</artifactId>
        <version>10.11.1.1</version>
        <scope>test</scope>
    </dependency>