code: @Nonnull
      public static MockSupplier createConstant (@Nonnull final Object aConstant)
      {
        ValueEnforcer.notNull (aConstant, "Constant");
        return new MockSupplier (aConstant.getClass (), null, aParam -> aConstant);
      }
docs: Create a mock supplier for a constant value.
  
  @param aConstant
  The constant value to be returned. May not be <code>null</code>.
  @return Never <code>null</code>.