Setting up the test environment

Let's adopt a test first approach here. So, before going into writing the queries and DAO classes, let's set up the environment for our unit testing. If you don't find the src/test/java and src/test/resources folders, then please go ahead and create them either from your IDE or from your OS file explorer.

The src/test/java folder will contain all the Java code and src/test/resources will contain the required property files and other resources required for test cases. After creating the required folders, the project structure looks something like that shown in the following screenshot:

We will use the H2 database as a source of data for our testing environment. For that, we will update our Maven dependencies to add H2 and JUnit dependencies. H2 is one of the most popular embedded databases. The following is the dependency information that you need to add in your pom.xml:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-test</artifactId>
    <version>${spring.version}</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>${junit.version}</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>org.assertj</groupId>
    <artifactId>assertj-core</artifactId>
    <version>${assertj.version}</version>
    <scope>test</scope>
</dependency>
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
    <version>${h2.version}</version>
</dependency>

We already have a property for spring.version, but we need version properties for the other two, as given in the following code:

<junit.version>4.12</junit.version>
<assertj.version>3.12.0</assertj.version>
<h2.version>1.4.198</h2.version>

The World DB schema available in MySQL will not be compatible to run with H2, but don't worry. The compatible World DB schema for H2 is available in the source code of this chapter, you can download from GitHub (https://github.com/PacktPublishing/Spring-5.0-Projects/tree/master/chapter01). It is kept in the src/test/resources folder in the project. The file name is h2_world.sql. We will use this file to bootstrap our H2 database with the required tables and data that will then be available in our tests.

Next up is to configure H2 and one of the things we configure is the name of the SQL script file that contains the schema and data. This SQL script file should be available on the classpath. The following is the configuration class created in the com.nilangpatel.worldgdp.test.config package under src/test/java folder:

@Configuration
public class TestDBConfiguration {
  
  @Bean
    public DataSource dataSource() {
        return new EmbeddedDatabaseBuilder()
            .generateUniqueName(true)
            .setType(EmbeddedDatabaseType.H2)
            .setScriptEncoding("UTF-8")
            .ignoreFailedDrops(true)
            .addScript("h2_world.sql")
            .build();
    }
  
  @Bean("testTemplate")
  public NamedParameterJdbcTemplate namedParamJdbcTemplate() {
    NamedParameterJdbcTemplate namedParamJdbcTemplate = 
        new NamedParameterJdbcTemplate(dataSource());
    return namedParamJdbcTemplate;
  }
}

Along with the H2 configuration, we are initializing NamedParameterJdbcTemplate by providing it with the H2 datasource built in the other method.