def METHOD_NAME(self):
    """
    _testFirstEventMC_
    Verify that we set the firstEvent parameter whenever the FirstEvent
    field in the job mask is a positive integer and the job is a production
    one. Otherwise we get a number based on the counter (modulo 2^32 - 1)
    """
    job = Job()
    job["input_files"] = [{"lfn": "MCFakeFile", "parents": []}]
    job["mask"] = Mask()
    job["counter"] = 5
    job["mask"]["FirstLumi"] = 200
    try:
        tweak = PSetTweak()
        WMTweaks.makeJobTweak(job, tweak)
        self.assertRaises(WMTweakMaskError,  WMTweaks.makeJobTweak, job)
    except WMTweakMaskError:
        pass
    job["mask"]["FirstEvent"] = 100
    tweak = PSetTweak()
    WMTweaks.makeJobTweak(job, tweak)
    self.assertFalse(hasattr(tweak.process.source, "skipEvents"),
                    "Error: There should be no skipEvents tweak, it's MC.")
    self.assertTrue(hasattr(tweak.process.source, "firstEvent"),
                    "Error: There should be a first event tweak")
    self.assertEqual(tweak.process.source.firstEvent, 'customTypeCms.untracked.uint32(100)',
                     "Error: The firstEvent tweak should be 100.")
    return