Neo4j: unit testing the bolt driver properly

Question

I am adding the Neo4j Bolt driver to my application just following the http://neo4j.com/developer/java/:

import org.neo4j.driver.v1.*;

Driver driver = GraphDatabase.driver( "bolt://localhost", AuthTokens.basic( "neo4j", "neo4j" ) );

Session session = driver.session();
session.run( "CREATE (a:Person {name:'Arthur', title:'King'})" );

StatementResult result = session.run( "MATCH (a:Person) WHERE a.name = 'Arthur' RETURN a.name AS name, a.title AS title" );

while ( result.hasNext() )

{
    Record record = result.next();
    System.out.println( record.get( "title" ).asString() + " " + record.get("name").asString() );
}
session.close();
driver.close();

However, always from the official documentation unit testing is made using:

GraphDatabaseService db = new TestGraphDatabaseFactory()
            .newImpermanentDatabaseBuilder()

So if I want to test in some way the code above, I have to replace the GraphDatabase.driver( "bolt://localhost",...) with the GraphDatabaseService from the test. How can I do that? I cannot extract any sort of in-memory driver from there as far as I can see.

score 2 · Accepted Answer · answered Jun 05 '16 at 09:16

2

The Neo4j JDBC has a class called Neo4jBoltRule for unit testing. It is a junit rule starting/stopping an impermanent database together with some configuration to start bolt.

The rule class uses dynamic port assignment to prevent test failure due to running multiple tests in parallel (think of your CI infrastructure).

An example of a unit test using that rule class is available at https://github.com/neo4j-contrib/neo4j-jdbc/blob/master/neo4j-jdbc-bolt/src/test/java/org/neo4j/jdbc/bolt/SampleIT.java

answered Jun 05 '16 at 09:16

Stefan Armbruster

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Thank you! It looks what I was looking for. However, is there any working maven repository for it? Or the only way to add the neo4j-jdbc package is including the jar? – Randomize Jun 05 '16 at 09:56
I found that until the 2nd milestone there is: "it.larus-ba" % "neo4j-jdbc" % "3.0-M02". For the 3rd milestone they are moving the groupId to "org.neo4j". – Randomize Jun 05 '16 at 10:10
I am wondering now what is the bare-minimum list of dependencies to use neo4j-bolt driver :) – Randomize Jun 05 '16 at 10:12
it was developed in the first place with a partner company and they've donated their code to neo4j-contrib. On mvn central it's currently at: http://mvnrepository.com/artifact/it.larus-ba - M03 has not yet been pushed to maven repo yet. Stay tuned. – Stefan Armbruster Jun 05 '16 at 10:18
The version M2 does not export Neo4jBoltRule. Is there any workaround? – Randomize Jun 05 '16 at 12:04
It's in `/src/test` and therefore not in the jar deployed to mvn central. I guess the easiest way is just copy&paste the code mentioned above to your project. – Stefan Armbruster Jun 05 '16 at 13:16
See below (late answer, I know) for an easier solution :-) – fbiville Apr 02 '17 at 15:50

fbiville · Answer 2 · 2017-04-02T15:52:15.147

An easy way now is to pull neo4j-harness, and use their built-in Neo4jRule as follows:

import static org.neo4j.graphdb.factory.GraphDatabaseSettings.boltConnector;
// [...]
@Rule public Neo4jRule graphDb = new Neo4jRule()
        .withConfig(boltConnector("0").address, "localhost:" + findFreePort());

Where findFreePort implementation can be as simple as:

private static int findFreePort() {
    try (ServerSocket socket = new ServerSocket(0)) {
        return socket.getLocalPort();
    } catch (IOException e) {
        throw new RuntimeException(e.getMessage(), e);
    }
}

As the Javadoc of ServerSocket explains:

A port number of 0 means that the port number is automatically allocated, typically from an ephemeral port range. This port number can then be retrieved by calling getLocalPort.

Moreover, the socket is closed before the port value is returned, so there are great chances the returned port will still be available upon return (the window of opportunity for the port to be allocated again in between is small - the computation of the window size is left as an exercise to the reader).

Et voilà !

Neo4j: unit testing the bolt driver properly

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