title: PowerMock with Mockito doesn't create mock for constructor invocations
body: <p>I'm trying to use PowerMock with mockito to create mock each time any constructor of FileOutputStream is created but it seems to return a real instance instead of a mocked one.</p>
  
  <p>My test class : </p>
  
  <pre><code>@RunWith(PowerMockRunner.class)
  @PrepareForTest({FileOutputStream.class,FilesHelper.class})
  public class FilesHelperTest {
  
  
  @Test
  public void createFileFromInputStream_validate_null_progress_subject_doesnt_throws_null_pointer() throws Exception {
      FileOutputStream fileOutputStream = Mockito.mock(FileOutputStream.class);
      PowerMockito.whenNew(FileOutputStream.class).withAnyArguments().thenReturn(fileOutputStream);
      File file = Mockito.mock(File.class);
      BufferedSource bufferedSource = Mockito.mock(BufferedSource.class);
      Mockito.doReturn(true).when(file).exists();
      Mockito.when(bufferedSource.read(Mockito.any(),Mockito.anyLong())).thenReturn(15L,-1L);
      FilesHelper.createFileFromInputStream(file,bufferedSource,8,null);
   }
  }
  </code></pre>
  
  <p>My class under test - </p>
  
  <pre><code>public class FilesHelper {
  
  /**
   * Creates a file out of an input stream wrapped by Okio's {@link BufferedSource}.
   * @param file a file to save the input to
   * @param bufferedSource the source input.
   * @param maxSize the maximum amount of bytes can be loaded to memory
   * @param progressUpdatePublisher an optional update publisher which notifies the writing progress
   * @return a {@link com.bonimoo.wominstaller.data.entities.BaseDownloadStatusDTO.Done} status with all the necessary information.
   * @throws IOException in case of errors while writing
   * @throws IllegalStateException when the file doesn't exists and cannot be created
   */
  public static BaseDownloadStatusDTO.Done createFileFromInputStream(File file, BufferedSource bufferedSource, int maxSize, @Nullable PublishSubject&lt;BaseDownloadStatusDTO&gt; progressUpdatePublisher) throws IOException, IllegalStateException {
      if (!file.exists()) {
          Throwable cause = null;
          boolean created = false;
          try {
              created = file.createNewFile();
          } catch (IOException e) {
              cause = e;
          }
          if (!created) {
              throw new IllegalStateException("FilesHelper cannot create new file",cause);
          }
      }
      if (progressUpdatePublisher != null) {
          progressUpdatePublisher.onNext(new BaseDownloadStatusDTO.Started(file.getAbsolutePath()));
      }
      BufferedSink sink = Okio.buffer(Okio.sink(file));
      Buffer buffer = new Buffer();
      long counter = 0L;
      try {
          for (long readCount = bufferedSource.read(buffer, maxSize); readCount &gt; -1 || bufferedSource.exhausted(); readCount = bufferedSource.read(buffer, maxSize)) {
              sink.writeAll(buffer);
              counter += readCount;
              if (progressUpdatePublisher != null) {
                  progressUpdatePublisher.onNext(new BaseDownloadStatusDTO.Progress(counter,file.getAbsolutePath(),readCount));
              }
          }
      } finally {
          sink.flush();
          sink.close();
          buffer.close();
          bufferedSource.close();
      }
      return new BaseDownloadStatusDTO.Done(file);
   }
  }
  </code></pre>
  
  <p>so when I'm creating the class I'm still getting the null pointer exception which thrown by the real constructor invocation</p>
  
  <pre><code>java.lang.NullPointerException
      at java.io.FileOutputStream.&lt;init&gt;(FileOutputStream.java:203)
      at java.io.FileOutputStream.&lt;init&gt;(FileOutputStream.java:162)
      at okio.Okio.sink(Okio.java:181)
      at com.bonimoo.wominstaller.data.helpers.FilesHelper.createFileFromInputStream(FilesHelper.java:49)
      at com.bonimoo.wominstaller.data.helpers.FilesHelperTest.createFileFromInputStream_validate_null_progress_subject_doesnt_throws_null_pointer(FilesHelperTest.java:36)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.junit.internal.runners.TestMethod.invoke(TestMethod.java:68)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:326)
      at org.junit.internal.runners.MethodRoadie$2.run(MethodRoadie.java:89)
      at org.junit.internal.runners.MethodRoadie.runBeforesThenTestThenAfters(MethodRoadie.java:97)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.executeTest(PowerMockJUnit44RunnerDelegateImpl.java:310)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTestInSuper(PowerMockJUnit47RunnerDelegateImpl.java:131)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.access$100(PowerMockJUnit47RunnerDelegateImpl.java:59)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner$TestExecutorStatement.evaluate(PowerMockJUnit47RunnerDelegateImpl.java:147)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.evaluateStatement(PowerMockJUnit47RunnerDelegateImpl.java:107)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit47RunnerDelegateImpl$PowerMockJUnit47MethodRunner.executeTest(PowerMockJUnit47RunnerDelegateImpl.java:82)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$PowerMockJUnit44MethodRunner.runBeforesThenTestThenAfters(PowerMockJUnit44RunnerDelegateImpl.java:298)
      at org.junit.internal.runners.MethodRoadie.runTest(MethodRoadie.java:87)
      at org.junit.internal.runners.MethodRoadie.run(MethodRoadie.java:50)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.invokeTestMethod(PowerMockJUnit44RunnerDelegateImpl.java:218)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.runMethods(PowerMockJUnit44RunnerDelegateImpl.java:160)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl$1.run(PowerMockJUnit44RunnerDelegateImpl.java:134)
      at org.junit.internal.runners.ClassRoadie.runUnprotected(ClassRoadie.java:34)
      at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:44)
      at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:136)
      at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:117)
      at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:57)
      at org.powermock.modules.junit4.PowerMockRunner.run(PowerMockRunner.java:59)
      at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
      at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
      at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
      at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
      at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
  </code></pre>