DDevelopment & Design

Custom SonarQube rules for Unit Tests

It’s a tutorial about creating new rules for SonarQube analysis to be applied to Unit Tests. It is not trivial and involves a few tricky database steps, so I want to share my tutorial about it.It’s a tutorial about creating new rules for SonarQube analysis to be applied to Unit Tests. It is not trivial and involves a few tricky database steps, so I want to share my tutorial about it.

I need a new rule

In our project we use (formely Sonar) to manage our code quality. It is a great tool and I recommend everyone to set it up and read its reports.

Recently, we’ve agreed that it’s better to use assertj assertions in our unit tests than JUnit’s. So I’ve decided to write a simple rule that checks if some of JUnit asserts assertTrue, assertFalse, assertNull and others are used. Then, I’ve discovered it’s not so easy to do it with Sonar:

  • only 10 code quality rules are applied to unit tests – they are in special repository PMD Unit Tests (source)
  • these 10 rules are disabled by default, you have to enable them by hand
  • you cannot add new rules to this group

However, it turned out it is doable with a small tricks.

Custom PMD Unit Tests rule tutorial

Create your XPath expression by following this tutorial on how to create custom PMD rule. There is a visual editor to test your rules as you develop them – that’s great. My XPath expression to avoid all JUnit assertions looks like this:

//PrimaryPrefix/Name[@Image='assertEquals' or @Image='assertNull' or @Image='assertNotNull' or @Image='assertSame' or @Image='assertNotSame' or @Image='assertArrayEquals' or @Image='assertTrue' or @Image='assertFalse']

Go to your Sonar installation, log in as an Administrator, head to Quality Profiles and select a profile that you use. Search for “xpath” and change Activation to Any. You should see two results like this:

Expand XPath rule template (dont’ worry that it says it’s deprecated) and then click Copy rule. Fill a form with message and XPath and save it. Then take a look at the bottom – you need an identifier of this rule:

You have created a PMD rule, now you need to move it to PMD Unit Tests group. Connect to Sonar’s MySQL database. Search for your rule by key:

mysql> select id, plugin_rule_key, plugin_name, parent_id, status from rules where plugin_rule_key='XPathRule_1385721910';
+-----+----------------------+----------------+-----------+-------------+
| id  | plugin_rule_key      | plugin_name    | parent_id | status      |
+-----+----------------------+----------------+-----------+-------------+
| 903 | XPathRule_1385721910 | pmd            | NULL      | DEPRECATED  |
+-----+----------------------+----------------+-----------+-------------+
1 row in set (0.00 sec)

Update plugin_name and status (remember to use appropiate primary key for id column):

mysql> update rules set plugin_name='pmd-unit-tests', status='READY' where id=903;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

There is one step left. Sonar will change this rule’s status to REMOVED on restart due to his boot checks. You need to trick him and change parent_id to other’s PMD Unit Tests rule. List all these rules and choose one’s identifier.

mysql> select id, plugin_name, status from rules where plugin_name='pmd-unit-tests';
+-----+----------------+---------+
| id  | plugin_name    | status  |
+-----+----------------+---------+
| 775 | pmd-unit-tests | READY   |
| 776 | pmd-unit-tests | READY   |
| 777 | pmd-unit-tests | READY   |
| 778 | pmd-unit-tests | READY   |
| 779 | pmd-unit-tests | READY   |
| 780 | pmd-unit-tests | READY   |
| 781 | pmd-unit-tests | READY   |
| 782 | pmd-unit-tests | READY   |
| 783 | pmd-unit-tests | READY   |
| 784 | pmd-unit-tests | READY   |
| 903 | pmd-unit-tests | READY   |
+-----+----------------+---------+
11 rows in set (0.00 sec)\

Choose any id you like, let’s say 775 and apply it as parent_id to your newly created rule:

mysql> update rules set parent_id=775 where id=903;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0

Go to your Quality profile and make sure your rule is active! Check it twice, it’s easy to forget that step. It’s all set up, enjoy your analysis!

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JBoss Envers and Spring transaction managers

I've stumbled upon a bug with my configuration for JBoss Envers today, despite having integration tests all over the application. I have to admit, it casted a dark shadow of doubt about the value of all the tests for a moment. I've been practicing TDD since 2005, and frankly speaking, I should have been smarter than that.

My fault was simple. I've started using Envers the right way, with exploratory tests and a prototype. Then I've deleted the prototype and created some integration tests using in-memory H2 that looked more or less like this example:

@Test
public void savingAndUpdatingPersonShouldCreateTwoHistoricalVersions() {
    //given
    Person person = createAndSavePerson();
    String oldFirstName = person.getFirstName();
    String newFirstName = oldFirstName + "NEW";

    //when
    updatePersonWithNewName(person, newFirstName);

    //then
    verifyTwoHistoricalVersionsWereSaved(oldFirstName, newFirstName);
}

private Person createAndSavePerson() {
    Transaction transaction = session.beginTransaction();
    Person person = PersonFactory.createPerson();
    session.save(person);
    transaction.commit();
    return person;
}    

private void updatePersonWithNewName(Person person, String newName) {
    Transaction transaction = session.beginTransaction();
    person.setFirstName(newName);
    session.update(person);
    transaction.commit();
}

private void verifyTwoHistoricalVersionsWereSaved(String oldFirstName, String newFirstName) {
    List<Object[]> personRevisions = getPersonRevisions();
    assertEquals(2, personRevisions.size());
    assertEquals(oldFirstName, ((Person)personRevisions.get(0)[0]).getFirstName());
    assertEquals(newFirstName, ((Person)personRevisions.get(1)[0]).getFirstName());
}

private List<Object[]> getPersonRevisions() {
    Transaction transaction = session.beginTransaction();
    AuditReader auditReader = AuditReaderFactory.get(session);
    List<Object[]> personRevisions = auditReader.createQuery()
            .forRevisionsOfEntity(Person.class, false, true)
            .getResultList();
    transaction.commit();
    return personRevisions;
}

Because Envers inserts audit data when the transaction is commited (in a new temporary session), I thought I have to create and commit the transaction manually. And that is true to some point.

My fault was that I didn't have an end-to-end integration/acceptance test, that would call to entry point of the application (in this case a service which is called by GWT via RPC), because then I'd notice, that the Spring @Transactional annotation, and calling transaction.commit() are two, very different things.

Spring @Transactional annotation will use a transaction manager configured for the application. Envers on the other hand is used by subscribing a listener to hibernate's SessionFactory like this:

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean" >        
...
 <property name="eventListeners">
     <map key-type="java.lang.String" value-type="org.hibernate.event.EventListeners">
         <entry key="post-insert" value-ref="auditEventListener"/>
         <entry key="post-update" value-ref="auditEventListener"/>
         <entry key="post-delete" value-ref="auditEventListener"/>
         <entry key="pre-collection-update" value-ref="auditEventListener"/>
         <entry key="pre-collection-remove" value-ref="auditEventListener"/>
         <entry key="post-collection-recreate" value-ref="auditEventListener"/>
     </map>
 </property>
</bean>

<bean id="auditEventListener" class="org.hibernate.envers.event.AuditEventListener" />

Envers creates and collects something called AuditWorkUnits whenever you update/delete/insert audited entities, but audit tables are not populated until something calls AuditProcess.beforeCompletion, which makes sense. If you are using org.hibernate.transaction.JDBCTransaction manually, this is called on commit() when notifying all subscribed javax.transaction.Synchronization objects (and enver's AuditProcess is one of them).

The problem was, that I used a wrong transaction manager.

<bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager" >
    <property name="dataSource" ref="dataSource"/>
</bean>

This transaction manager doesn't know anything about hibernate and doesn't use org.hibernate.transaction.JDBCTransaction. While Synchronization is an interface from javax.transaction package, DataSourceTransactionManager doesn't use it (maybe because of simplicity, I didn't dig deep enough in org.springframework.jdbc.datasource), and thus Envers works fine except not pushing the data to the database.

Which is the whole point of using Envers.

Use right tools for the task, they say. The whole problem is solved by using a transaction manager that is well aware of hibernate underneath.

<bean id="transactionManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager" >
    <property name="sessionFactory" ref="sessionFactory"/>
</bean>

Lesson learned: always make sure your acceptance tests are testing the right thing. If there is a doubt about the value of your tests, you just don't have enough of them,