Add factory fixture example to documentation.

Close #3461

Author: NiklasMM

changelog/3461.doc.rst

@@ -0,0 +1 @@
+Added a section on how to use fixtures as factories to the fixture documentation.

doc/en/fixture.rst

@@ -465,6 +465,59 @@ Running it::
 voila! The ``smtp`` fixture function picked up our mail server name
 from the module namespace.
 
+.. _`fixture-factory`:
+
+Factories as fixtures
+-------------------------------------------------------------
+
+The "factory as fixture" pattern can help in situations where the result
+of a fixture is needed multiple times in a single test. Instead of returning
+data directly, the fixture instead returns a function which generates the data.
+This function can then be called multiple times in the test.
+
+Factories can have have parameters as needed::
+
+    @pytest.fixture
+    def make_customer_record():
+
+        def _make_customer_record(name):
+            return {
+                "name": name,
+                "orders": []
+            }
+
+        return _make_customer_record
+
+
+    def test_customer_records(make_customer_record):
+        customer_1 = make_customer_record("Lisa")
+        customer_2 = make_customer_record("Mike")
+        customer_3 = make_customer_record("Meredith")
+
+If the data created by the factory requires managing, the fixture can take care of that::
+
+    @pytest.fixture
+    def make_customer_record():
+
+        created_records = []
+
+        def _make_customer_record(name):
+            record = models.Customer(name=name, orders=[])
+            created_records.append(record)
+            return record
+
+        yield _make_customer_record
+
+        for record in created_records:
+            record.destroy()
+
+
+    def test_customer_records(make_customer_record):
+        customer_1 = make_customer_record("Lisa")
+        customer_2 = make_customer_record("Mike")
+        customer_3 = make_customer_record("Meredith")
+
+
 .. _`fixture-parametrize`:
 
 Parametrizing fixtures