JarCastingjunit-customclassloader
Introduction
Run your test using a custom classloader!
Installation
Maven
<dependency>
<groupId>com.github.mjeanroy</groupId>
<artifactId>junit-customclassloader</artifactId>
<version>0.1.0</version>
<scope>test</scope>
</dependency>
How to use
Run your test with CustomClassLoaderRunner and add RunWithClassLoader annotation to specify the classloader to use in your unit tests!
For example, here a unit test that will run only on Windows:
import org.junit.Test;
import org.junit.runner.RunWith;
import com.github.mjeanroy.junit4.customclassloader.BlackListClassLoaderHolder;
import com.github.mjeanroy.junit4.customclassloader.CustomClassLoaderRunner;
import com.github.mjeanroy.junit4.customclassloader.RunWithClassLoader;
@RunWith(CustomClassLoaderRunner.class)
@RunWithClassLoader(BlackListClassLoaderHolder.class)
public class MyUnitTest {
@Test
public void it_should_run_with_custom_class_loader() {
// Do your test
}
}
Why?
Sometimes, you may have to write code that depends on classpath detection: think about a library where you want to load a different implementation if a library is available in the classpath.
In this case, you will probably have this kind of function:
public final class MyFactory {
private MyFactory() {
}
public static MyLib create() {
if (isAvailable("com.org.my.optional.dependency")) {
return new MyOptionalLibImpl();
}
return new MyDefaultImpl();
}
private static boolean isAvailable(String className) {
try {
Class.forName(className, false, Thread.currentThread().getContextClassLoader());
return true;
} catch(ClassNotFoundException ex) {
return false;
}
}
}
Then, it is hard to unit test this function: you have to create a fake classloader to test both case. Here is how you can do that with junit-customclassloader:
import org.junit.Test;
import org.junit.runner.RunWith;
import com.github.mjeanroy.junit4.customclassloader.BlackListClassLoader;
import com.github.mjeanroy.junit4.customclassloader.BlackListClassLoaderHolder;
import com.github.mjeanroy.junit4.customclassloader.CustomClassLoaderRunner;
import com.github.mjeanroy.junit4.customclassloader.RunWithClassLoader;
import com.github.mjeanroy.junit4.customclassloader.TestClassLoader;
@RunWith(CustomClassLoaderRunner.class)
@RunWithClassLoader(BlackListClassLoaderHolder.class)
public class MyUnitTest {
@Test
public void it_should_load_default_impl() {
getClassLoader().add("com.org.my.optional.dependency");
Assert.asserEquals(MyFactory.create().getClass(), MyDefaultImpl.class);
}
private BlackListClassLoader getClassLoader() {
// With the CustomClassLoaderRunner, each test is runned in its own thread, so it is safe
// to get the current thread classloader like this.
return (BlackListClassLoader) Thread.currentThread().getContextClassLoader();
}
}
License
MIT License.
Contributing
If you found a bug or you thing something is missing, feel free to contribute and submit an issue or a pull request.