compiler could see that...

I recently have met one of those not straightforward exceptions in tests. Something I first classified as 'perhaps it's config or classpath issue'. Here comes the stacktrace:

java.lang.NullPointerException
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.junit.internal.runners.ClassRoadie.runAfters(ClassRoadie.java:72)
 at org.junit.internal.runners.ClassRoadie.runProtected(ClassRoadie.java:47)
 at org.powermock.modules.junit4.internal.impl.PowerMockJUnit44RunnerDelegateImpl.run(PowerMockJUnit44RunnerDelegateImpl.java:133)
 at org.powermock.modules.junit4.common.internal.impl.JUnit4TestSuiteChunkerImpl.run(JUnit4TestSuiteChunkerImpl.java:112)
 at org.powermock.modules.junit4.common.internal.impl.AbstractCommonPowerMockRunner.run(AbstractCommonPowerMockRunner.java:57)
 at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:236)
 at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:134)
 at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:113)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.apache.maven.surefire.util.ReflectionUtils.invokeMethodWithArray(ReflectionUtils.java:189)
 at org.apache.maven.surefire.booter.ProviderFactory$ProviderProxy.invoke(ProviderFactory.java:165)
 at org.apache.maven.surefire.booter.ProviderFactory.invokeProvider(ProviderFactory.java:85)
 at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:103)
 at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:74)

When I looked at the tests I was able to see all test methods are successful, but after there is an error. I was able to figure out that NPE is thrown during invocation of method within clean up method that should be run after test. Here is the code:

 @AfterClass
 public void resetConf() throws Exception{
  setTestConfiguration();
 }

Can you see that?
In debugger I have found that first argument of invoke() is null.
But it's quite ok. If it's null it's just static invocation and that's what I would expect during @AfterClass call...
Yes. Fine.
But resetConf() must be static then, you stupid reflection!