Improve the test coverage for util.py (#114)

Add requests-mock dependency.

dev-requirements.txt

@@ -2,3 +2,4 @@
 pytest==3.6.2
 pytest-asyncio==0.8.0
 pytest-aiohttp==0.3.0
+requests-mock==1.5.0

miss_islington/util.py

@@ -24,6 +24,7 @@ def comment_on_pr(issue_number, message):
     else:
         print(response.status_code)
         print(response.text)
+    return response
 
 
 def assign_pr_to_core_dev(issue_number, coredev_login):
@@ -44,6 +45,7 @@ def assign_pr_to_core_dev(issue_number, coredev_login):
     else:
         print(response.status_code)
         print(response.text)
+    return response
 
 
 async def leave_comment(gh, pr_number, message):

tests/test_util.py

@@ -123,3 +123,50 @@ def test_pr_is_awaiting_merge():
 def test_pr_is_not_awaiting_merge():
     labels = [{"name": "CLA Signed", "name": "skip issue", "name": "awaiting review"}]
     assert util.pr_is_awaiting_merge(labels) is False
+
+
+def test_comment_on_pr_success(requests_mock):
+    issue_number = 100
+    message = "Thanks for the PR!"
+    post_url = (
+        f"https://api.github.com/repos/python/cpython/issues/{issue_number}/comments"
+    )
+    requests_mock.post(
+        post_url,
+        json={
+            "html_url": "https://github.com/python/cpython/pull/{issue_number}#issuecomment-401309376"
+        },
+        status_code=201,
+    )
+    response = util.comment_on_pr(issue_number, message)
+    assert response.status_code == 201
+
+
+def test_comment_on_pr_failure(requests_mock):
+    issue_number = 100
+    message = "Thanks for the PR!"
+    post_url = (
+        f"https://api.github.com/repos/python/cpython/issues/{issue_number}/comments"
+    )
+    requests_mock.post(post_url, status_code=400)
+    response = util.comment_on_pr(issue_number, message)
+    assert response.status_code == 400
+
+
+def test_assign_pr_to_coredev_success(requests_mock):
+
+    issue_number = 100
+    coredev_login = "Mariatta"
+    patch_url = f"https://api.github.com/repos/python/cpython/issues/{issue_number}"
+    requests_mock.patch(patch_url, status_code=201)
+    response = util.assign_pr_to_core_dev(issue_number, coredev_login)
+    assert response.status_code == 201
+
+
+def test_assign_pr_to_coredev_failed(requests_mock):
+    issue_number = 100
+    coredev_login = "Mariatta"
+    patch_url = f"https://api.github.com/repos/python/cpython/issues/{issue_number}"
+    requests_mock.patch(patch_url, status_code=400)
+    response = util.assign_pr_to_core_dev(issue_number, coredev_login)
+    assert response.status_code == 400