Make Django's assertion helpers available in pytest_django.asserts (#709)

Fixes #97.

Co-authored-by: Daniel Hahler <github@thequod.de>

Author: wgordon17

docs/helpers.rst

@@ -3,6 +3,16 @@
 Django helpers
 ==============
 
+Assertions
+----------
+
+All of Django's :py:class:`~django:django.test.TestCase`
+:ref:`django:assertions` are available in ``pytest_django.asserts``, e.g.
+
+::
+
+    from pytest_django.asserts import assertTemplateUsed
+
 Markers
 -------
 

pytest_django/asserts.py

@@ -0,0 +1,34 @@
+"""
+Dynamically load all Django assertion cases and expose them for importing.
+"""
+from functools import wraps
+from django.test import (
+    TestCase, SimpleTestCase,
+    LiveServerTestCase, TransactionTestCase
+)
+
+test_case = TestCase('run')
+
+
+def _wrapper(name):
+    func = getattr(test_case, name)
+
+    @wraps(func)
+    def assertion_func(*args, **kwargs):
+        return func(*args, **kwargs)
+
+    return assertion_func
+
+
+__all__ = []
+assertions_names = set()
+assertions_names.update(
+    set(attr for attr in vars(TestCase) if attr.startswith('assert')),
+    set(attr for attr in vars(SimpleTestCase) if attr.startswith('assert')),
+    set(attr for attr in vars(LiveServerTestCase) if attr.startswith('assert')),
+    set(attr for attr in vars(TransactionTestCase) if attr.startswith('assert')),
+)
+
+for assert_func in assertions_names:
+    globals()[assert_func] = _wrapper(assert_func)
+    __all__.append(assert_func)

tests/test_asserts.py

@@ -0,0 +1,56 @@
+"""
+Tests the dynamic loading of all Django assertion cases.
+"""
+import inspect
+
+import pytest
+import pytest_django
+
+from pytest_django.asserts import __all__ as asserts_all
+
+
+def _get_actual_assertions_names():
+    """
+    Returns list with names of all assertion helpers in Django.
+    """
+    from django.test import TestCase as DjangoTestCase
+    from unittest import TestCase as DefaultTestCase
+
+    obj = DjangoTestCase('run')
+
+    def is_assert(func):
+        return func.startswith('assert') and '_' not in func
+
+    base_methods = [name for name, member in
+                    inspect.getmembers(DefaultTestCase)
+                    if is_assert(name)]
+
+    return [name for name, member in inspect.getmembers(obj)
+            if is_assert(name) and name not in base_methods]
+
+
+def test_django_asserts_available():
+    django_assertions = _get_actual_assertions_names()
+    expected_assertions = asserts_all
+    assert set(django_assertions) == set(expected_assertions)
+
+    for name in expected_assertions:
+        assert hasattr(pytest_django.asserts, name)
+
+
+@pytest.mark.django_db
+def test_sanity():
+    from django.http import HttpResponse
+    from pytest_django.asserts import assertContains, assertNumQueries
+
+    response = HttpResponse('My response')
+
+    assertContains(response, 'My response')
+    with pytest.raises(AssertionError):
+        assertContains(response, 'Not my response')
+
+    assertNumQueries(0, lambda: 1 + 1)
+    with assertNumQueries(0):
+        pass
+
+    assert assertContains.__doc__