It would be nice to improve the javadocs for
http://googlecloudplatform.github.io/google-cloud-java/0.9.2/apidocs/com/google/cloud/datastore/testing/LocalDatastoreHelper.html

Especially the docs for reset look like generated docs string :). Please tell when one would call reset.

E.g. Does this setup for junit make sense? What bout including the code snippet into the docs?

  private static final LocalDatastoreHelper datastoreHelper = ...

  @BeforeClass
  public static void setUpOnce() throws Exception {
    datastoreHelper.start();
  }

  @AfterClass
  public static void tearDownOnce() throws Exception {
    datastoreHelper.stop(Duration.ofSeconds(5));
  }

  @Before
  public void setUp() throws Exception {
    datastoreHelper.reset();
  }

For start()/stop() it would be interesting to be explicit and tell if there is going to be any state (e.g. should I call reset() before calling stop()).