ClassNotFoundException on static inner class

I'm getting a ClassNotFoundException using Class.forName() passing the fully qualified name of a public static class that lives inside the same package. This is when running my tests.

Here's the full stacktrace.

In EntitySerializerTests.java inside my tests folder.

package com.badlogic.ashley.serialization;
public class EntitySerializerTests {

    public static class TestComponentA implements Component {
        public int value;
    }

    ...
}

In my library code

package com.badlogic.ashley.serialization;
public class EntitySerializer implements Json.Serializer<Entity> {
    ...

    private Component read(Json json, JsonValue componentValue) throws ClassNotFoundException {
        String className = componentValue.name();
        Class componentType = Class.forName(className); // THROWS
        ...
    }
}

The exception message is:

java.lang.ClassNotFoundException: com.badlogic.ashley.serialization.EntitySerializerTests.TestComponentA

Library code is trying to get the Class given the name for a class that's defined in a test file. Is that allowed? I would assume that, at runtime, all these classes are available in the class path.

Thanks.