Django form test only fails when breakpoint set on form.is_valid() in PyCharm

I have a model called Table:

class Table(models.Model):
    """
    Models tables which are initially scanned by customers. Orders are linked to tables
    """
    MINIMUM_QR_WIDTH, MINIMUM_QR_HEIGHT = 115, 115
    MAX_QR_SIZE = 10485760  # 10MB

    number = models.CharField(max_length=256, blank=False, null=False)

    identifier = models.UUIDField(default=uuid.uuid4, unique=True, editable=False)
    venue = models.ForeignKey(Venue, null=False, blank=False, on_delete=models.CASCADE)
    qr_code = models.ImageField(upload_to='table_qr_codes', blank=True, null=True)

    def __str__(self):
        return "Table " + self.number

    class Meta:
        unique_together = ('venue', 'number')
        ordering = ['venue', 'number']

I have a ModelForm to create Table objects called TableAddForm.

class TableAddForm(forms.ModelForm):

    class Meta:
        model = Table
        fields = ['number', 'qr_code', 'venue']

    def clean_qr_code(self):
        qr = self.cleaned_data.get('qr_code')

        if qr:
            w, h = get_image_dimensions(qr)
            if w < Table.MINIMUM_QR_WIDTH or h < Table.MINIMUM_QR_HEIGHT:
                msg = forms.ValidationError("The image you selected is too small. QR codes must be at least " + str(Table.MINIMUM_QR_WIDTH)
                                            + "px by " + str(Table.MINIMUM_QR_HEIGHT) + "px.")
                self.add_error('qr_code', msg)

            if qr.size > Table.MAX_QR_SIZE:
                msg = forms.ValidationError("The file you uploaded is too large. File size can be up to " + str(size(Table.MAX_QR_SIZE))
                                            + ". File size is currently " + str(size(qr.size)))
                self.add_error('logo', msg)

        return qr

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.fields['venue'].empty_label = 'Select your venue'

I have a test for the TableAddForm.

class TableAddFormTests(TestCase):
    def setUp(self):
        user = User.objects.create(username='john1@email.com', password='password', email='john1@email.com')
        business1 = create_business(name='business1', owner=user)
        venue = create_venue(name='venue1', address='address1', zip='zip1', city='city1', country='country1', business=business1)

    def test_valid_data(self):
        qr = SimpleUploadedFile(name='valid_qr.png', content=open('media/tests/225_by_225_image.png', 'rb').read())
        venue = get_object_or_404(Venue, name='venue1')
        data = {'number': 1, 'venue': venue.pk}
        form = TableAddForm(data=data, files={'qr_code': qr})
        self.assertTrue(form.is_valid())
        table = form.save()
        self.assertEqual(table.number, '1')
        self.assertEqual(table.venue, venue)
        self.assertEqual(open('media/tests/225_by_225_image.png', 'rb').read(), table.qr_code.read())

  
When I run test_valid_data() without breakpoints in PyCharm, it passes. When I run the test with a break point on: "self.assertTrue(form.is_valid()) two things happen.
  
1. The breakpoints on Django's_clean_fields() method are ignored (i.e. code execution is not stopped at the breakpoints).
  
2. The venue key is not present in the form's cleaned_data dictionary (as can be seen in the screenshot below). This leads to an integrity error when I try to save the form as Table objects must 
have a Venue foreign key.



















Fig 1. Screenshot of debugger variables just before I call form.save() if I have set a breakpoint on form.is_valid()
Traceback when I attempt to save the form without a Venue in cleaned_data.
  
Error  Traceback (most recent call last):    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute      return self.cursor.execute(sql, params)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/sqlite3/base.py", line 296, in execute      return Database.Cursor.execute(self, query, params)  sqlite3.IntegrityError: NOT NULL constraint failed: sk_business_table.venue_id    The above exception was the direct cause of the following exception:    Traceback (most recent call last):    File "/Users/williamdavies/Documents/PyCharmProjects/SwiftKiosk_new/swiftkiosk/sk_business/test_forms.py", line 322, in test_valid_data      table = form.save()    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/forms/models.py", line 458, in save      self.instance.save()    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/base.py", line 717, in save      force_update=force_update, update_fields=update_fields)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/base.py", line 747, in save_base      updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/base.py", line 830, in _save_table      result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/base.py", line 868, in _do_insert      using=using, raw=raw)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/manager.py", line 82, in manager_method      return getattr(self.get_queryset(), name)(*args, **kwargs)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/query.py", line 1133, in _insert      return query.get_compiler(using=using).execute_sql(return_id)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1285, in execute_sql      cursor.execute(sql, params)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/utils.py", line 68, in execute      return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/utils.py", line 77, in _execute_with_wrappers      return executor(sql, params, many, context)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute      return self.cursor.execute(sql, params)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/utils.py", line 89, in __exit__      raise dj_exc_value.with_traceback(traceback) from exc_value    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/utils.py", line 85, in _execute      return self.cursor.execute(sql, params)    File "/Users/williamdavies/.virtualenvs/swiftkiosknew/lib/python3.6/site-packages/django/db/backends/sqlite3/base.py", line 296, in execute      return Database.Cursor.execute(self, query, params)  django.db.utils.IntegrityError: NOT NULL constraint failed: sk_business_table.venue_id    Destroying test database for alias 'default'...    Process finished with exit code 1
    
When I run the test with a breakpoint on any other line, the problem is not reproduced and the breakpoints in Django's _clean_fields() method are called. It seems that setting a breakpoint on the line where 
I call form.is_valid() changes the way the form data is cleaned and the venue foreign key is not processed correctly, leading to its absence in cleaned_data.

Thanks for reading through this and any help would really be appreciated! If you need any other code/tracebacks/screenshots etc that I missed please let me know and I'd be happy to provide!

Will
            

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