Revision as of 07:58, 21 June 2010

Testing

Virgo also has a strong emphasis on testing. Unit tests check the behaviour of individual classes or small groups of classes. Integration tests check the behaviour of groups of Virgo bundles running together in Equinox. System verification tests (SVTs), including some simple performance tests, check the behaviour of packaging builds of the kernel and web server from a user's perspective.

JUnit is used for all these types of tests. Each testcase is structured as a class with class name ending in Tests. Tests typically reside in the src/test/java folder of a project.

If you need a thorough introduction to Test Driven Development, we recommend "Growing Object-Oriented Software Guided by Tests". This book makes the important point that unless test code is as clean as the code under test, the tests will inevitably end up slowing down the whole project. Good test coverage enables changes to be made with confidence, so test code should be refactored and kept clean just like the code under test.

Unit Tests

Each unit test tests a small unit, typically a single class. Dependencies are usually stubbed or mocked out.

Stubs are hand-written, dummy implementations of interfaces just sufficient to simulate the behaviour of a full implementation of the interface and in some cases to check that the interface has been used correctly. Stubs for several standard OSGi interfaces are provided in the OSGi Test Stubs git repository. Other projects may supply stubs for commonly used interfaces. For example, the Quasi Framework interfaces have stubs [add link once kernel checked in] provided.

Mocks are generated on the fly from interfaces. EasyMock is typically used. Expectations of how an interface is used can be set and checked. It is important not to code expectations that are too specific to an implementation otherwise the resultant test will be fragile and is likely to break if the implementation being tested is refactored.

Some tests of complex classes use a combination of stubs and mocks.

In general, unit tests aim to provide at least 80% coverage of Virgo code, but some components fall short of this and more tests need to be written. The precommit ant target used to check coverage using Clover, but this check is not currently supported as the Eclipse Hudson server does not support Clover.

Some complex classes are simply too messy to unit test and refactoring is required to enable maintainable unit tests to be created. So if significant refactoring of existing code is planned, that is often a good time to add a suite of unit tests.

New code should be written with unit tests from the start. This is the only way to make sure that code can be thoroughly unit tested.

Integration Tests

Integration tests install a collection of bundles into Equinox and then run the testcase as part of a bundle. Some integration tests install sufficient bundles to start a Virgo kernel or web server, but others install a relatively small subset.

Virgo tests are implemented using JUnit and EasyMock. In addition, integration tests which require an OSGi environment use the Virgo test framework.

Virgo Test Framework

The Virgo Test Framework is maintained in its own git repository. It is fairly primitive, providing just two test runners and an annotation.

Test Runners

The test framework provides the following test runners.

OsgiTestRunner

The OsgiTestRunner is for testing components that need a simple OSGi environment. It is invoked via the JUnit @RunWith class annotation, for example:

import org.junit.runner.RunWith;
import org.eclipse.virgo.test.framework.OsgiTestRunner;

@RunWith(OsgiTestRunner.class)
public class EventLogIntegrationTests { ...

OsgiTestRunner launches Equinox, installs the project containing the testcase class as a bundle, starts the bundle, and then runs the testcase class from inside the bundle using a standard JUnit runner.

DmKernelTestRunner

The DmKernelTestRunner, which should probably be renamed to VirgoKernelTestRunner, is for testing components that need a Virgo kernel environment complete with kernel and user regions. It must be used in combination with suitable configuration to launch the kernel bundles and the bundle on which the kernel depends.

It is invoked via the JUnit @RunWith class annotation, for example:

import org.junit.runner.RunWith;
import org.eclipse.virgo.test.framework.dmkernel.DmKernelTestRunner;
 
@RunWith(DmKernelTestRunner.class)
public abstract class AbstractKernelIntegrationTest { ...

The DmKernelTestRunner extends the function of the OsgiTestRunner to wait for the user region to start before running the testcase.

Annotations

Test Configuration

The test configuration file specifies a list of bundles to be installed and optionally started as well as kernel and other properties.

The Virgo web layer has a fairly typical configuration file.

Utilities

The standard OSGi utility class FrameworkUtil is used to obtain the test bundle context as in the following example:

protected final BundleContext testBundleContext = FrameworkUtil.getBundle(getClass()).getBundleContext();

Automated Testing

Test dependencies are either checked in to src/test/resources or are downloaded into an Ivy repository when the tests are built.

The unit and integration tests of a Virgo git repository can be run by changing into the build-xxx directory and issuing:

ant clean clean-integration test

This will halt when the first test fails. To run all the tests and not halt on failure, issue:

ant -Dci.build=true clean clean-integration test

and, since this will always report "build successful", remember to open target/test-results/index.html at the end to see which tests passed and which failed.

System Verification Tests

SVTs are present in the Virgo Kernel System Verification Tests and the Virgo System Verification Tests repositories. Building these repositories runs the test. The latter project requires a package web server zip file to be placed in build-svt/target/artifacts/ before the following ant target is run:

ant test-svt

Performance Tests

A small number of SVTs in the Virgo Performance Tests git repository check that the performance of Virgo does not worsen. These tests are very approximate since it is impossible to enforce precise performance goals when tests are run in a general CI server which may be subject to fluctuation in its load and performance.

Ignoring Tests

Ignoring a failing test is always a last resort. If this is required, then a bug must be raised and the failing test method or, in rare situations, the whole test class should be annotated using the org.junit.Ignore annotation:

@Ignore("bug <bugzilla number>: <reason for ignoring the test>")

The bug should also detail which test or tests are ignored.