How to create unit tests against non in-memory database such as MySQL in Play framework, with resetting to known state?

Question

I want to create unit tests that cover code that use relational database in Play framework 2.1.0. There are many possibilities for this and all cause problems:

Testing on in-memory H2 database

Play framework documentation proposes to run unit tests on H2 in-memory database, even if main database used for development and production use other software (i.e. MySQL):

app = Helpers.fakeApplication(Helpers.inMemoryDatabase());

My application don't use complicated RDBMS features such as stored procedures and most database access cases are ebean calls, so it should be compatible with both MySQL and H2.

However, table creation statements in evolutions use MySQL-specific features, such as specifying ENGINE = InnoDB, DEFAULT CHARACTER SET = utf8, etc. I fear if I will remove these proprietary parts of CREATE TABLE, MySQL will use some default setting that I can't control and that depend on version, so to test and develop application main MySQL config must be modified.

Anybody used this approach (making evolutions compatible with both MySQL and H2)?

Other ideas how it can be handled:

• Separate evolutions for MySQL and H2 (not a good idea)
• Some way to make H2 ignore additional MySQL stuff in create table (MySQL compatibility mode don't work, it still complain even on default character set). I don't know how.

Testing on the same database driver as main database

The only advantage of H2 in-memory database that it is fast, and testing on the same database driver than dev/production database may be better, because it is closer to real environment.

How it can be done right in Play framework?

Tried:

Map<String, String> settings = new HashMap<String, String>();
settings.put("db.default.url", "jdbc:mysql://localhost/sometestdatabase");
settings.put("db.default.jndiName", "DefaultDS");
app = Helpers.fakeApplication(settings);

Looks like evolutions work here, but how it's best to clean database before each test? By creating custom code that truncates each table? If it will drop tables, then will evolutions run again before next test, or they are applied once per play test command? Or once per Helpers.fakeApplication() invocation?

What are best practices here? Heard about dbunit, is it possible to integrate it without much pain and quirks?

Freaky

Did you get anywhere with this? – Demos

Answer 1

First, I would recommend you to use the same RDBMS for testing and production as it could avoid some hard-to-find bugs.

Concerning the need to clean your database between each test, you can use Ebean DdlGenerator to generate scripts to create a clean database and JUnit's @Before annotation to automatically execute these scripts before every test.

Using the DdlGenerator can be done like this :

    EbeanServer server = Ebean.getServer(serverName);
    ServerConfig config = new ServerConfig();
    DdlGenerator ddl = new DdlGenerator((SpiEbeanServer) server, new MySqlPlatform(), config);

This code can be placed in a base-class that you could make inherit your tests (or inside a custom Runner that you can use with the @RunWith annotation).

It will also allow you to easily automate the FakeApplication creation, avoiding some boilerplate code.

Some links that can be helpful :

• http://blog.matthieuguillermin.fr/2012/03/unit-testing-tricks-for-play-2-0-and-ebean/
• https://gist.github.com/nboire/2819920

Beverage

Do your code use the same database as main application database for running tests, or there is something in application.conf making tests automatically use separate database? – Freaky

@Beverage Could you please see this question? #20623540 – Boastful

@Boastful I've answered your question. – Beverage

@mguillermin, can I use external databases in a real play framework project? Cause I heard that 2.0 doesn't support except from H2. – Glaring

Answer 2

I used the same database engine that main database and dbunit for cleaning up before each test.

public class SomeTest {
    // ...

    @Before
    public void startApp() throws Exception {
        // Set up connection to test database, different from main database. Config better should be used instead of hard-coding.
        Map<String, String> settings = new HashMap<String, String>();
        settings.put("db.default.url", "jdbc:mysql://localhost/somedatabase?characterEncoding=UTF-8&useOldAliasMetadataBehavior=true");
        settings.put("db.default.user", "root");
        settings.put("db.default.password", "root");
        settings.put("db.default.jndiName", "DefaultDS"); // make connection available to dbunit through JNDI
        app = Helpers.fakeApplication(settings);
        Helpers.start(app);

        databaseTester = new JndiDatabaseTester("DefaultDS");

        IDataSet initialDataSet = new FlatXmlDataSetBuilder().build(play.Play.application()
                .resourceAsStream("/resources/dataset.xml"));
        databaseTester.setDataSet(initialDataSet);
        databaseTester.onSetup();
    }

    @After
    public void stopApp() throws Exception {
        databaseTester.onTearDown();
        Helpers.stop(app);
    }
}

My dataset.xml just contain table names to tell dbunit to empty these tables before each test. It also can contain fixtures.

<?xml version="1.0" encoding="UTF-8"?>
<dataset>
  <name_of_my_first_table />
  <name_of_my_second_table />
</dataset>

Evolutions run automatically on test database when using this approach, so if you remove all tables from test database, they will be recreated.

It is overkill to use dbunit if you only need to clean tables, you can clean them by issuing query directly or by using ebean DdlGenerator. But I also use dbunit for comparing data.

I don't use Helpers.running, because it takes Runnable and Runnable implementations cannot throw exceptions - very inconvenient for tests. But if you look at code for running(), it just calls Helpers.start() and Helpers.stop() so I call these methods directly in @Before and @After.

Decided not to use H2 for running tests: yes, it runs faster, but there are too much difference between it and MySQL.

Freaky

Answer 3

Anybody used this approach (making evolutions compatible with both MySQL and H2)?

I have found an answer for the MySQL specific features: How can I unit test for MySQL database with Play 2.x?

Nuke

Answer 4

When I wrote my tests for my postgres database I simply created a HashMap to connect to the database, and then I wrote test queries to make sure correct amount of records exists and so on... Here is my code.

    @Test
public void testDataBase() {
    final HashMap<String,String> postgres = new HashMap<String, String>();
    postgres.put("db.default.driver","org.postgresql.Driver");
    postgres.put("db.default.url","jdbc:postgresql://localhost/myDataBase");
    postgres.put("db.default.user", "postgres");
    postgres.put("db.default.password", "password");

    running(fakeApplication(postgres), new Runnable() {

        @Override
        public void run() {

            //Insert Assertions Here
        }
    });
}

Beshore

Answer 5

You can also using DB mock, if goal is to validate both your Slick|JPA|Anorm mappings & functions based on.

When it's fit it has advantage to be more compliant with unit testing than a test DB, and more easy to manage (not setup/clear tasks, not sync of tests to avoid access to same test tables).

You can have a look at my framework Acolyte ( http://github.com/cchantep/acolyte ) which is used in specs of Anorm itself (e.g. https://github.com/playframework/playframework/blob/master/framework/src/anorm/src/test/scala/anorm/SqlResultSpec.scala ).

Rechaba