public Task OutputNullAsync()
 {
     return(Assert.ThrowsExceptionAsync <InvalidConstraintException>(() => UsesThrowHelpers.ReturnAllowNullParameterNonNullReturnAsync(null)));
 }
 public void OutputNull()
 {
     Assert.ThrowsException <InvalidDataException>(() => UsesThrowHelpers.ReturnNullableParameterNonNullReturn(null));
 }