Remove test_ prefix from methods called by other tests

Methods test_retrieve_single and test_retrieve_single_by_device got
called from other methods. In case any of the caller functions fail when
calling any of these two functions, the callee is shown as failing. This
hides what test actually failed.

This change renames the callees so that the callers are shown when they
fail.

Issue: HIC-98
Change-Id: Ia61afbcb53f3fe46c9545538a52d197f6db90461
diff --git a/crashreports/tests.py b/crashreports/tests.py
index 5e1b6c4..f40ea60 100644
--- a/crashreports/tests.py
+++ b/crashreports/tests.py
@@ -201,42 +201,49 @@
         self.assertEqual(request.status_code, status.HTTP_200_OK)
         self.assertTrue(len(request.data['results']) == count)
 
-    def test_retrieve_single(self, user=None,
-                             expected_result=status.HTTP_200_OK):
+    def retrieve_single(self, user):
         count = 5
-        if user is None:
-            user = self.admin
         self.post_multiple(self.user, self.data, count)
         url = "{}1/".format(self.url)
         request = user.get(url)
-        self.assertEqual(request.status_code, expected_result)
+        return request.status_code
+
+    def test_retrieve_single_admin(self):
+        self.assertEqual(
+            self.retrieve_single(self.admin),
+            status.HTTP_200_OK)
 
     def test_retrieve_single_noauth(self):
-        self.test_retrieve_single(user=self.user,
-                                  expected_result=status.HTTP_403_FORBIDDEN)
+        self.assertEqual(
+            self.retrieve_single(self.user),
+            status.HTTP_403_FORBIDDEN)
 
     def test_retrieve_single_device_owner(self):
-        self.test_retrieve_single(self.noauth_client,
-                                  status.HTTP_401_UNAUTHORIZED)
+        self.assertEqual(
+            self.retrieve_single(self.noauth_client),
+            status.HTTP_401_UNAUTHORIZED)
 
-    def test_retrieve_single_by_device(self, user=None,
-                                       expected_result=status.HTTP_200_OK):
+    def retrieve_single_by_device(self, user):
         count = 5
-        if user is None:
-            user = self.admin
         self.post_multiple(self.user, self.data, count)
         url = "{}1/".format(self.url_by_uuid.format(self.uuid))
         request = user.get(url)
-        self.assertEqual(request.status_code, expected_result)
+        return request.status_code
+
+    def test_retreive_single_by_device_admin(self):
+        self.assertEqual(
+            self.retrieve_single_by_device(self.admin),
+            status.HTTP_200_OK)
 
     def test_retrieve_single_by_device_noauth(self):
-        self.test_retrieve_single_by_device(
-            user=self.user,
-            expected_result=status.HTTP_403_FORBIDDEN)
+        self.assertEqual(
+            self.retrieve_single_by_device(self.user),
+            status.HTTP_403_FORBIDDEN)
 
     def test_retrieve_single_by_device_device_owner(self):
-        self.test_retrieve_single_by_device(
-            self.noauth_client, status.HTTP_401_UNAUTHORIZED)
+        self.assertEqual(
+            self.retrieve_single_by_device(self.noauth_client),
+            status.HTTP_401_UNAUTHORIZED)
 
     def test_list_by_uuid(self):
         count = 5