fails:Kernel#singleton_class returns class extended from an object
fails:Kernel#singleton_class returns NilClass for nil
fails:Kernel#singleton_class returns TrueClass for true
fails:Kernel#singleton_class returns FalseClass for false
fails:Kernel#singleton_class raises TypeError for Fixnum
fails:Kernel#singleton_class raises TypeError for Symbol
fails:Kernel#singleton_class? returns true for singleton classes
fails:Kernel#singleton_class? returns false for other objects
fails:Kernel#singleton_class? with singleton values returns false for nil's singleton class
fails:Kernel#singleton_class? with singleton values returns false for true's singleton class
fails:Kernel#singleton_class? with singleton values returns false for false's singleton class
