How to generate the data of post request for flask_wtf Form in test

I have a form as following:

from flask_wtf import Form

    class MyForm(Form):
        domain = StringField('domain')
        hosts = StringField('hosts')
        startdate = StringField('Start Date', validators=[InputRequired()])
        enddate = StringField('End Date', validators=[InputRequired()] )
        starthour = SelectField('Start Hour',coerce=int, choices=[(i, i) for i in range(0, 24)], default=0)
        endhour = SelectField('End Hour',coerce=int, choices=[(i, i) for i in range(0, 24)], default=23)
        submit1 = SubmitField('Submit1')
        submit2 = SubmitField('Submit2')

I try to test it using unittest:

 def test_form(self):
    form = {
    "domain": "fake",
    "hosts": "fake",
    "startdate": "fake",
    "enddate": "fake",
    "starthour": 1,
    "endhour": 2,
    'submit1': True,
    'submit2': False
    }
    response = self.client.post(url_for('/'), data=form)

But though the printed received data looks correct, the function form.validate_on_submit() can never pass. Does anyone here know the write way to feed the form data for post request?

Thanks,