Here's the magic to get ActionBarSherlock working with Robolectric 2.0-alpha-2!

00_README.md

You need to add the files below, and do this once in your base test runner:

ActionBarSherlock.registerImplementation(ActionBarSherlockRobolectric.class);
ActionBarSherlock.unregisterImplementation(ActionBarSherlockNative.class);
ActionBarSherlock.unregisterImplementation(ActionBarSherlockCompat.class);

ActionBarSherlockRobolectric.java

// Copyright 2012 Square, Inc. License: Apache 2.
package com.squareup.test;

import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import com.actionbarsherlock.ActionBarSherlock;
import com.actionbarsherlock.app.ActionBar;
import com.actionbarsherlock.internal.ActionBarSherlockCompat;
import com.actionbarsherlock.internal.ActionBarSherlockNative;
import com.actionbarsherlock.view.MenuInflater;
import com.squareup.test.actionbarsherlock.SherlockMenuInflater;

import static org.robolectric.Robolectric.shadowOf;

/**
 * During initialization, {@link ActionBarSherlock} figures out which {@link
 * com.actionbarsherlock.app.ActionBar} to use based on the API level. It does this by checking the
 * Build.Version.SDK_INT value which depends on the hidden <i>SystemProperties</i> class.
 *
 * Because Roboelectric does not have this, it always returns <code>0</code> for its API level
 * causing {@link ActionBarSherlock} to crash. This class helps resolve this issue by providing
 * an {@link ActionBarSherlockNative} implementation for API level 0.
 * @see ActionBarSherlock#registerImplementation(Class)
 */
@ActionBarSherlock.Implementation(api = 0)
public class ActionBarSherlockRobolectric extends ActionBarSherlockCompat {
  final private ActionBar actionBar;

  public ActionBarSherlockRobolectric(Activity activity, int flags) {
    super(activity, flags);
    actionBar = new MockActionBar(activity);
  }

  @Override public void setContentView(int layoutResId) {
    LayoutInflater layoutInflater = LayoutInflater.from(mActivity);
    View contentView = layoutInflater.inflate(layoutResId, null);

    shadowOf(mActivity).setContentView(contentView);
  }

  @Override public void setContentView(View view) {
    shadowOf(mActivity).setContentView(view);
  }

  @Override public ActionBar getActionBar() {
    return actionBar;
  }

  @Override protected Context getThemedContext() {
    return mActivity;
  }

  @Override public MenuInflater getMenuInflater() {
    if (mMenuInflater == null) {
      mMenuInflater = new SherlockMenuInflater(mActivity);
    }
    return mMenuInflater;
  }
}

MockActionBar.java

// Copyright 2012 Square, Inc. License: Apache 2.
package com.squareup.test;

import android.content.Context;
import android.graphics.drawable.Drawable;
import android.view.View;
import android.widget.SpinnerAdapter;
import com.actionbarsherlock.app.ActionBar;

public class MockActionBar extends ActionBar {
  String title;
  String subtitle;
  View customView;
  Context realContext;

  public MockActionBar(Context context) {
    realContext = context;
  }

  @Override public void setCustomView(View view) {
    setCustomView(view,  null);
  }

  @Override public void setCustomView(View view, LayoutParams layoutParams) {
    this.customView = view;
  }

  @Override public void setCustomView(int resId) {
  }

  @Override public void setIcon(int resId) {
  }

  @Override public void setIcon(Drawable icon) {
  }

  @Override public void setLogo(int resId) {
  }

  @Override public void setLogo(Drawable logo) {
  }

  @Override
  public void setListNavigationCallbacks(SpinnerAdapter adapter, OnNavigationListener callback) {
  }

  @Override public void setSelectedNavigationItem(int position) {
  }

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

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

  @Override public void setTitle(CharSequence title) {
    this.title = (String) title;
  }

  @Override public void setTitle(int resId) {
    title = realContext.getString(resId);
  }

  @Override public void setSubtitle(CharSequence newSubtitle) {
    subtitle = (String) newSubtitle;
  }

  @Override public void setSubtitle(int resId) {
    subtitle = realContext.getString(resId);
  }

  @Override public void setDisplayOptions(int options) {
  }

  @Override public void setDisplayOptions(int options, int mask) {
  }

  @Override public void setDisplayUseLogoEnabled(boolean useLogo) {
  }

  @Override public void setDisplayShowHomeEnabled(boolean showHome) {
  }

  @Override public void setDisplayHomeAsUpEnabled(boolean showHomeAsUp) {
  }

  @Override public void setDisplayShowTitleEnabled(boolean showTitle) {
  }

  @Override public void setDisplayShowCustomEnabled(boolean showCustom) {
  }

  @Override public void setBackgroundDrawable(Drawable d) {
  }

  @Override public View getCustomView() {
    return customView;
  }

  @Override public CharSequence getTitle() {
    return title;
  }

  @Override public CharSequence getSubtitle() {
    return subtitle;
  }

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

  @Override public void setNavigationMode(int mode) {
  }

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

  @Override public Tab newTab() {
    return null;
  }

  @Override public void addTab(Tab tab) {
  }

  @Override public void addTab(Tab tab, boolean setSelected) {
  }

  @Override public void addTab(Tab tab, int position) {
  }

  @Override public void addTab(Tab tab, int position, boolean setSelected) {
  }

  @Override public void removeTab(Tab tab) {
  }

  @Override public void removeTabAt(int position) {
  }

  @Override public void removeAllTabs() {
  }

  @Override public void selectTab(Tab tab) {
  }

  @Override public Tab getSelectedTab() {
    return null;
  }

  @Override public Tab getTabAt(int index) {
    return null;
  }

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

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

  @Override public void show() {
  }

  @Override public void hide() {
  }

  @Override public boolean isShowing() {
    return false;
  }

  @Override public void addOnMenuVisibilityListener(OnMenuVisibilityListener listener) {
  }

  @Override
  public void removeOnMenuVisibilityListener(OnMenuVisibilityListener listener) {
  }
}

SherlockMenuInflater.java

// Copyright 2012 Square, Inc. License: Apache 2.
package com.squareup.test.actionbarsherlock;

import android.content.Context;
import android.util.AttributeSet;
import com.actionbarsherlock.view.Menu;
import com.actionbarsherlock.view.MenuInflater;
import com.actionbarsherlock.view.SubMenu;
import org.robolectric.internal.Implementation;
import org.robolectric.res.MenuNode;
import org.robolectric.res.ResName;
import org.robolectric.res.ResourceLoader;
import org.robolectric.util.I18nException;

import static org.robolectric.Robolectric.shadowOf;

/**
 * Inflates menus that are part of ActionBarSherlock instead. Uses ABS custom {@link
 * com.actionbarsherlock.view.Menu} instead of the stock one.
 */
public class SherlockMenuInflater extends MenuInflater {
  private final Context context;

  public SherlockMenuInflater(Context context) {
    super(context);
    this.context = context;
  }

  @Implementation
  public void inflate(int resource, Menu root) {
    String qualifiers = shadowOf(context.getResources().getConfiguration()).getQualifiers();
    ResourceLoader resourceLoader = shadowOf(context).getResourceLoader();
    ResName resName = shadowOf(context).getResName(resource);
    MenuNode menuNode = resourceLoader.getMenuNode(resName, qualifiers);

    try {
      addChildrenInGroup(menuNode, 0, root);
    } catch (I18nException e) {
      throw e;
    } catch (Exception e) {
      throw new RuntimeException("error inflating " + resName, e);
    }
  }

  private void addChildrenInGroup(MenuNode source, int groupId, Menu root) {
    for (MenuNode child : source.getChildren()) {
      String name = child.getName();
      AttributeSet attributes = shadowOf(context).createAttributeSet(child.getAttributes(), null);
      if (name.equals("item")) {
        if (child.isSubMenuItem()) {
          SubMenu sub = root.addSubMenu(groupId,
              attributes.getAttributeResourceValue("android", "id", 0),
              0, attributes.getAttributeValue("android", "title"));
          MenuNode subMenuNode = child.getChildren().get(0);
          addChildrenInGroup(subMenuNode, groupId, sub);
        } else {
          root.add(groupId,
              attributes.getAttributeResourceValue("android", "id", 0),
              0, attributes.getAttributeValue("android", "title"));
        }
      } else if (name.equals("group")) {
        int newGroupId = attributes.getAttributeResourceValue("android", "id", 0);
        addChildrenInGroup(child, newGroupId, root);
      }
    }
  }
}

Christian, do you have a moment to change this to something like MIT or Apache license?

is this still needed for Robolectric 2.1.1?