34.6. Basic unit testing

The basic pattern of unit testing with Neo4j is illustrated by the following example.

To access the Neo4j testing facilities you should have the neo4j-kernel tests.jar on the classpath during tests. You can download it from Maven Central: org.neo4j:neo4j-kernel.

Using Maven as a dependency manager you would typically add this dependency together with JUnit and Hamcrest like so:

Maven dependency. 

<project>
...
 <dependencies>
  <dependency>
   <groupId>org.neo4j</groupId>
   <artifactId>neo4j-kernel</artifactId>
   <version>2.2-SNAPSHOT</version>
   <type>test-jar</type>
   <scope>test</scope>
  </dependency>
  <dependency>
   <groupId>junit</groupId>
   <artifactId>junit-dep</artifactId>
   <version>4.11</version>
   <scope>test</scope>
  </dependency>
  <dependency>
   <groupId>org.hamcrest</groupId>
   <artifactId>hamcrest-all</artifactId>
   <version>1.3</version>
   <scope>test</scope>
  </dependency>
  ...
 </dependencies>
...
</project>

Observe that the <type>test-jar</type> is crucial. Without it you would get the common neo4j-kernel jar, not the one containing the testing facilities.

With that in place, we’re ready to code our tests.

[Tip]Tip

For the full source code of this example see: Neo4jBasicDocTest.java

Before each test, create a fresh database:

@Before
public void prepareTestDatabase()
{
    graphDb = new TestGraphDatabaseFactory().newImpermanentDatabase();
}

After the test has executed, the database should be shut down:

@After
public void destroyTestDatabase()
{
    graphDb.shutdown();
}

During a test, create nodes and check to see that they are there, while enclosing write operations in a transaction.

Node n = null;
try ( Transaction tx = graphDb.beginTx() )
{
    n = graphDb.createNode();
    n.setProperty( "name", "Nancy" );
    tx.success();
}

// The node should have a valid id
assertThat( n.getId(), is( greaterThan( -1L ) ) );

// Retrieve a node by using the id of the created node. The id's and
// property should match.
try ( Transaction tx = graphDb.beginTx() )
{
    Node foundNode = graphDb.getNodeById( n.getId() );
    assertThat( foundNode.getId(), is( n.getId() ) );
    assertThat( (String) foundNode.getProperty( "name" ), is( "Nancy" ) );
}

If you want to set configuration parameters at database creation, it’s done like this:

GraphDatabaseService db = new TestGraphDatabaseFactory()
    .newImpermanentDatabaseBuilder()
    .setConfig( GraphDatabaseSettings.mapped_memory_total_size, "512M" )
    .setConfig( GraphDatabaseSettings.string_block_size, "60" )
    .setConfig( GraphDatabaseSettings.array_block_size, "300" )
    .newGraphDatabase();