A.java

package lt.segfoltas.breathcount;

import android.os.Parcel;
import android.os.Parcelable;
import android.support.annotation.Nullable;

public class A implements Parcelable {
    private int mInt;
    @Nullable private A mA;

    public A(int mInt, A mA) {
        this.mInt = mInt;
        this.mA = mA;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        A a = (A) o;

        if (mInt != a.mInt) return false;
        return mA != null ? mA.equals(a.mA) : a.mA == null;

    }

    @Override
    public int hashCode() {
        int result = mInt;
        result = 31 * result + (mA != null ? mA.hashCode() : 0);
        return result;
    }

    @Override
    public int describeContents() {
        return 0;
    }

    @Override
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(this.mInt);
        dest.writeParcelable(this.mA, flags);
    }

    public A() {
    }

    protected A(Parcel in) {
        this.mInt = in.readInt();
        this.mA = in.readParcelable(A.class.getClassLoader());
    }

    public static final Parcelable.Creator<A> CREATOR = new Parcelable.Creator<A>() {
        @Override
        public A createFromParcel(Parcel source) {
            return new A(source);
        }

        @Override
        public A[] newArray(int size) {
            return new A[size];
        }
    };
}

ATest.java

package lt.segfoltas.breathcount;

import android.os.Parcel;

import org.hamcrest.CoreMatchers;
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.robolectric.RobolectricGradleTestRunner;
import org.robolectric.annotation.Config;

import static org.hamcrest.CoreMatchers.*;
import static org.junit.Assert.*;


@RunWith(RobolectricGradleTestRunner.class)
@Config(
        constants = BuildConfig.class,
        sdk = 21,
        application = TestApplication.class)
public class ATest {

    @Test
    public void testParcel() throws Exception {
        A empty = new A(5, null);
        A full = new A(6, empty);
        Parcel parcel = Parcel.obtain();
        parcel.writeParcelable(empty, 0);
        parcel.writeParcelable(full, 0);
        parcel.setDataPosition(0);

        A readEmpty = parcel.readParcelable(null);
        A readFull = parcel.readParcelable(null);

        assertThat(readEmpty, is(empty));
        assertThat(readFull, is(full));
    }
}