title: Provider org.togglz.slf4j.Slf4jLogProvider not a subtype
body: <p>I have a library, built with Maven, that uses Spring 4.0.3.RELEASE and Togglz 2.2.0.Final. I'm trying to write a JUnit 4.11 test of my Spring class and running into the following error on the first test that gets executed:</p>
  
  <pre><code>testCreateItem_throwsItemServiceBusinessException(impl.ItemServiceImplTest)  Time elapsed: 1.771 sec  &lt;&lt;&lt; ERROR!
  java.util.ServiceConfigurationError: org.togglz.core.spi.LogProvider: 
  Provider org.togglz.slf4j.Slf4jLogProvider not a subtype
  </code></pre>
  
  <p>Here is the relevant java test snippet:</p>
  
  <pre><code>@RunWith(SpringJUnit4ClassRunner.class)
  @ContextConfiguration(classes = AppConfig.class, loader = AnnotationConfigContextLoader.class)
  @PrepareForTest({ ItemServiceImpl.class })
  public class ItemServiceImplTest {
     @Rule
     public TogglzRule togglzRule = TogglzRule.allDisabled(Features.class);
  
     @Rule
     public PowerMockRule powerMockRule = new PowerMockRule();
  
     @Test(expected = ItemServiceBusinessException.class)
     public void testCreateItem_throwsItemServiceBusinessException() throws Exception {
        PowerMockito.doReturn(mockMetricsData).when(serviceUnderTest, START_METRICS_METHOD_NAME, any(MetricsOperationName.class), any(RequestContext.class));
  
        when(mockDao.createItem(any(Item.class), any(RequestContext.class))).thenThrow(dataBusinessException);
  
        serviceUnderTest.createItem(item, context);
  
        verify(mockItemServiceValidator).validate(any(Item.class), any(RequestContext.class));
  
        PowerMockito.verifyPrivate(serviceUnderTest).invoke(START_METRICS_METHOD_NAME, any(MetricsOperationName.class), any(RequestContext.class));
  
        verify(mockDao).createItem(any(Item.class), any(RequestContext.class));
     }
  }
  </code></pre>
  
  <p>Subsequent test calls get the following error:</p>
  
  <pre><code>java.lang.NoClassDefFoundError: Could not initialize class org.togglz.junit.TogglzRule
  </code></pre>
  
  <p>Here are some relevant dependencies I have:</p>
  
  <pre><code> org.mockito:mockito-all=org.mockito:mockito-all:jar:1.9.5:compile,
   org.powermock:powermock-module-junit4=org.powermock:powermock-module-junit4:jar:1.5.6:test,org.powermock:powermock-module-junit4-common=org.powermock:powermock-module-junit4-common:jar:1.5.6:test,
   org.powermock:powermock-reflect=org.powermock:powermock-reflect:jar:1.5.6:test,
   org.powermock:powermock-api-mockito=org.powermock:powermock-api-mockito:jar:1.5.6:test,
   org.powermock:powermock-api-support=org.powermock:powermock-api-support:jar:1.5.6:test,
   org.powermock:powermock-module-junit4-rule=org.powermock:powermock-module-junit4-rule:jar:1.5.6:test,
   org.powermock:powermock-classloading-base=org.powermock:powermock-classloading-base:jar:1.5.6:test,
   org.powermock:powermock-core=org.powermock:powermock-core:jar:1.5.6:test,
   org.powermock:powermock-classloading-xstream=org.powermock:powermock-classloading-xstream:jar:1.5.6:test,
   org.togglz:togglz-core=org.togglz:togglz-core:jar:2.2.0.Final:compile,
   org.togglz:togglz-slf4j=org.togglz:togglz-slf4j:jar:2.2.0.Final:compile,
   org.togglz:togglz-spring-core=org.togglz:togglz-spring-core:jar:2.2.0.Final:compile,
   org.togglz:togglz-testing=org.togglz:togglz-testing:jar:2.2.0.Final:test,
   org.togglz:togglz-junit=org.togglz:togglz-junit:jar:2.2.0.Final:test
  </code></pre>
  
  <p>And I have provided a LogProvider (<code>org.togglz.slf4j.Slf4jLogProvider</code>) via SPI, located at <code>META-INF/serivces/org.togglz.core.spi.LogProvider</code></p>
  
  <p>This error is baffling as Slf4jLogProvider should be assignable from LogProvider. Sorry for the verbosity, but I wanted to try and show a complete picture. The code in class "under test" is making a call to see if a single feature is enabled inside the create method.</p>