CODEWITHSUNDEEP
springunit-testingtestingdependency-injectionintegration-testing
Anand Patel
Anand Patel

Reputation: 6431

Using Spring Framework's @Autowired for instantiating and injecting SUT (System Under Test) in the test fixture

I have seen developers using Spring's @Autowired feature making Spring framework responsible for instantiating and injecting SUT (System Under Test) or CUT (Class Under Test) in the test class or fixture. The following is the snippet showing @Autowired being used in the test fixture:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.annotation.ExpectedException;
import org.springframework.test.context.testng.AbstractTestNGSpringContextTests;
import org.springframework.test.context.ContextConfiguration;



interface BackingStore
{
    //Some methods
}


class Logger
{
    public Logger(BackingStore backingStore)
    {
        //Capture input parameter into member variables
    }

    public void Log(String message) 
    {
        //Some logic
    }
}

@ContextConfiguration(locations = { "classpath:someconfig.xml" })
public class LoggerTests extends AbstractTestNGSpringContextTests
{
    @Autowired
    private Logger _logger;

    @Test
    @ExpectedException(NullPointerException)
    public void Log_WhenPassedNull_ShouldThrowException()
    {
        _logger.Log(null);
    }
}

All the dependencies (recursively) required by the SUT are specified as part of the Spring configuration XML file. I do not like this approach. I like all the test (unit or integration) to read like a story (I heard Kent Beck saying the same thing :)). I like instantiating SUT/CUT in the test case itself even though if it is complex. This gives a clear picture about the test case.

I have few concerns regarding @Autowired or any auto injection mechanism being used for injecting SUT in the test fixture:

  1. It reduces test code readability. @Autowire appears like magic. Arrange of AAA (Arrange-Act-Assert) moves to XML file from test code.

  2. It reduces test code maintainability. This is because of #2.

  3. Could not effectively verify constructor of SUT/CUT throwing exception in exceptional cases. I am not 100% sure about this. I do not know if Spring framework has an answer for this.

  4. It seems overkill for unit or integration tests.

I ask experts for 2 cents on this subject.

Thanks.

Upvotes: 0

Views: 834

Answers (1)

cowls
cowls

Reputation: 24354

It only reduces test code readability if you dont know where to look for the @Autowired objects. I would advise using SpringJunitTestRunner that defines the test application context at the top of the unit test class.

Using dependency injection in your test cases allows you to easily test with different objects.

E.g. If your code required a 3rd party service, you could use dependency injection (e.g. Autowiring a Spring bean) to inject a mocked service for your unit tests and the real service for the application.

So for this reason it definitley doesnt decrease the test code maintainability, as it is really encouraging loose coupling between the code youre testing and any external objects.

It may be overkill to inject all objects in such a way, but it is definitely not overkill for unit tests/integration tests in general.

Upvotes: 1

Related Questions