Tested class is calling actual object, instead of mocked object

I'm trying to mock an external library, however the actual object created in APKDecompiler is being used, instead of the mock object.

Test code

import com.googlecode.dex2jar.v3.Dex2jar;
import jd.core.Decompiler;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.api.easymock.PowerMock;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import APKDecompiler;

import static org.easymock.EasyMock.expect;
import static org.easymock.EasyMock.expectLastCall;
import static org.junit.Assert.assertEquals;
import static org.powermock.api.easymock.PowerMock.*;

import java.io.File;
import java.io.IOException;

@RunWith(PowerMockRunner.class)
@PrepareForTest({Dex2jar.class})
public class TestAPKDecompiler {
   //As this only uses external libraries, I will only test that they are called correctly by mocking them.
    @Test
    public void testAPKDecompiler() {
        try {
            File testFile = new File("ApkExtractor/src/test/resources/testApp.jar");
            String expectedDirectory = testFile.getAbsolutePath().substring(0, testFile.getAbsolutePath().length() - 4);
            mockStatic(Dex2jar.class);
            Dex2jar mockApkToProcess = createMock(Dex2jar.class);
            Decompiler mockDecompiler = createNiceMockAndExpectNew(Decompiler.class);


            expect(Dex2jar.from(testFile)).andStubReturn(mockApkToProcess);

            mockApkToProcess.to(new File(expectedDirectory + ".jar"));
            expectLastCall();

            PowerMock.expectNew(Decompiler.class).andReturn(mockDecompiler).anyTimes();

            expect(mockDecompiler.decompileToDir(expectedDirectory + ".jar", expectedDirectory)).andReturn(0);


            replay(mockApkToProcess);
            PowerMock.replay(mockDecompiler);
            replayAll();
            String actualDirectory = APKDecompiler.decompileAPKToDirectory(testFile);

            verify(mockApkToProcess);
            verify(mockDecompiler);
            verifyAll();

            assertEquals(expectedDirectory, actualDirectory);
            testFile.delete();
        }
        catch(Exception e){
            e.printStackTrace();
        }
    }
}

Class code

import com.googlecode.dex2jar.v3.Dex2jar;
import jd.core.Decompiler;
import jd.core.DecompilerException;

import java.io.File;
import java.io.IOException;

public class APKDecompiler {
    public static String decompileAPKToDirectory(File filename) throws IOException, DecompilerException {
        String filenameWithoutFileExtension = filename.getAbsolutePath().substring(0, filename.getAbsolutePath().length() - 4);
        Dex2jar apkToProcess = Dex2jar.from(filename);
        File jar = new File(filenameWithoutFileExtension + ".jar");
        apkToProcess.to(jar);
        Decompiler decompiler = new Decompiler();

        decompiler.decompileToDir(filenameWithoutFileExtension + ".jar", filenameWithoutFileExtension);

        return filenameWithoutFileExtension;
    }

I've tried this and I haven't had any luck. EasyMock: Mocked object is calling actual method

I get a FileNotFoundException when decompiler.decompileToDir is called, which shouldn't happen as I should be mocking the class.

Any help would be greatly appreciated.