RNJ RNJ - 5 months ago 21
Java Question

Assert an object is a specific type

Is it possible in JUnit to assert an object is an instance of a class? For various reasons I have an object in my test that I want to check the type of. Is it a type of Object1 or a type of Object2?

Currently I have:

assertTrue(myObject instanceof Object1);
assertTrue(myObject instanceof Object2);


This works but I was wondering if there is a more expressive way of doing this.

For example something like:

assertObjectIsClass(myObject, Object1);


I could do this:

assertEquals(myObject.class, Object1.getClass());


Is there a specific assert method that allows me to test a type of an object in a more elegant, fluid manner?

Answer

You can use the assertThat method and the Matchers that comes with JUnit.

Take a look at this link that describes a little bit about the JUnit Matchers.

Example:

public class BaseClass {
}

public class SubClass extends BaseClass {
}

Test:

import org.junit.Test;

import static org.hamcrest.CoreMatchers.instanceOf;
import static org.junit.Assert.assertThat;

/**
 * @author maba, 2012-09-13
 */
public class InstanceOfTest {

    @Test
    public void testInstanceOf() {
        SubClass subClass = new SubClass();
        assertThat(subClass, instanceOf(BaseClass.class));
    }
}
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