Django formset unit test

It is in fact easy to reproduce whatever is in the formset by inspecting the context of the response.

Consider the code below (with self.client being a regular test client):

url = "some_url"

response = self.client.get(url)
self.assertEqual(response.status_code, 200)

# data will receive all the forms field names
# key will be the field name (as "formx-fieldname"), value will be the string representation.
data = {}

# global information, some additional fields may go there
data['csrf_token'] = response.context['csrf_token']

# management form information, needed because of the formset
management_form = response.context['form'].management_form
for i in 'TOTAL_FORMS', 'INITIAL_FORMS', 'MIN_NUM_FORMS', 'MAX_NUM_FORMS':
    data['%s-%s' % (management_form.prefix, i)] = management_form[i].value()

for i in range(response.context['form'].total_form_count()):
    # get form index 'i'
    current_form = response.context['form'].forms[i]

    # retrieve all the fields
    for field_name in current_form.fields:
        value = current_form[field_name].value()
        data['%s-%s' % (current_form.prefix, field_name)] = value if value is not None else ''

# flush out to stdout
print '#' * 30
for i in sorted(data.keys()):
    print i, '\t:', data[i]

# post the request without any change
response = self.client.post(url, data)

Important note

If you modify data prior to calling the self.client.post, you are likely mutating the DB. As a consequence, subsequent call to self.client.get might not yield to the same data, in particular for the management form and the order of the forms in the formset (because they can be ordered differently, depending on the underlying queryset). This means that

• if you modify data[form-3-somefield] and call self.client.get, this same field might appear in say data[form-8-somefield],
• if you modify data prior to a self.client.post, you cannot call self.client.post again with the same data: you have to call a self.client.get and reconstruct data again.

Every Django formset comes with a management form that needs to be included in the post. The official docs explain it pretty well. To use it within your unit test, you either need to write it out yourself. (The link I provided shows an example), or call formset.management_form which outputs the data.

In particular, I've found that the ManagmentForm validator is looking for the following items to be POSTed:

form_data = {
            'form-TOTAL_FORMS': 1, 
            'form-INITIAL_FORMS': 0 
}