python - 尝试在方法上使用 mock.patch 时出现 ModuleNotFoundError

Question

我的 pytest 单元测试不断返回错误 ModuleNotFoundError: No module name billing .

奇怪的是send_invoices当我删除补丁语句时，可以调用计费模块中的方法。如果是这种情况，为什么 mock.patch 无法找到计费模块并修补方法？
billing.py

import pdfkit
from django.template.loader import render_to_string
from django.core.mail import EmailMessage
from projectxapp.models import User

Class Billing:

  #creates a pdf of invoice. Takes an invoice dictionary
  def create_invoice_pdf(self, invoice, user_id):
    #get the html of the invoice
    file_path ='/{}-{}.pdf'.format(user_id, invoice['billing_period'])
    invoice_html = render_to_string('templates/invoice.html', invoice)
    pdf = pdfkit.from_file(invoice_html, file_path)
    return file_path, pdf

  #sends invoice to customer
  def send_invoices(self, invoices):
    for user_id, invoice in invoices.items():
            #get customers email
            email = User.objects.get(id=user_id).email
            billing_period = invoice['billing_period']
            invoice_pdf = self.create_invoice_pdf(invoice, user_id)
            email = EmailMessage(
                'Statement of credit: {}-{}'.format(user_id, billing_period),
                'Attached is your statement of credit.\
                This may also be viewed on your dashboard when you login.',
                'no-reply@trevoe.com',
                [email],
            ).attach(invoice_pdf)

            email.send(fail_silently=False)

        return True

test.py

from mock import patch
from projectxapp import billing

@pytest.mark.django_db
def test_send_invoice():
  invoices = {
    1: {
        'transaction_processing_fee': 2.00,
        'service_fee': 10.00,
        'billing_period': '2020-01-02'
    },
    2: {
        'transaction_processing_fee': 4.00,
        'service_fee': 20.00,
        'billing_period': '2020-01-02'
    }
 }

  with patch('services.billing.Billing().create_invoice_pdf') as p1:
    p1.return_value = '/invoice.pdf'
    test = billing.Billing().send_invoices(invoices)

  assert test == True

Answer 1

当你使用 patch 时，你应该指定模块的完整路径，包括包名。 .另外，不要在路径中使用括号。修改return_value Mock 的属性对象自定义调用对象的返回值:

with patch('projectxapp.billing.Billing.create_invoice_pdf') as p1:
    p1.return_value = '/invoice.pdf'
    test = billing.Billing().send_invoices(invoices)