code: static void assertConstructorIsPrivateAndCall(Class<?> cls) {
          Constructor<?> constructor;
          try {
              constructor = cls.getDeclaredConstructor();
          } catch (NoSuchMethodException e1) {
              throw new RuntimeException("private constructor without arguments not found", e1);
          } catch (SecurityException e1) {
              throw new RuntimeException(e1);
          }
          assertTrue("constructor is not private", Modifier.isPrivate(constructor.getModifiers()));
          constructor.setAccessible(true);
          try {
              constructor.newInstance();
          } catch (InstantiationException e) {
              throw new RuntimeException(e);
          } catch (IllegalAccessException e) {
              throw new RuntimeException(e);
          } catch (IllegalArgumentException e) {
              throw new RuntimeException(e);
          } catch (InvocationTargetException e) {
              // don't care if constructor threw an exception!
          }
      }
docs: Checks that a class has a no-argument private constructor and calls that
  constructor to instantiate the class (usually for code coverage
  purposes).
  
  @param <T>
  type of class being checked
  @param cls
  class being checked