Add boilerplate for sending SMS via Reach

This works in conjunction with the new SMS provider stub [^1].

Local testing:

- Run the migrations to add Reach as an inactive provider.
- Activate the Reach provider locally and deactivate the others.

      update provider_details set priority = 100, active = false where notification_type = 'sms';
      update provider_details set active = true where identifier = 'reach';

- Tweak your local environment to point at the SMS stub.

      export REACH_URL="http://host.docker.internal:6300/reach"

- Start / restart Celery to pick up the config change.
- Send a SMS via the Admin app and see the stub log it.
- Reset your environment so you can send normal SMS.

      update provider_details set active = true where notification_type = 'sms';
      update provider_details set active = false where identifier = 'reach';

[^1]: https://github.com/alphagov/notifications-sms-provider-stub/pull/10

tests/app/clients/test_reach.py

@@ -1 +1,93 @@
-# TODO: all of the tests
+import pytest
+import requests_mock
+from requests import HTTPError
+from requests.exceptions import ConnectTimeout, ReadTimeout
+
+from app import reach_client
+from app.clients.sms import SmsClientResponseException
+from app.clients.sms.reach import ReachClientResponseException
+
+# TODO: tests for get_reach_responses
+
+
+def test_try_send_sms_successful_returns_reach_response(notify_api, mocker):
+    to = content = reference = 'foo'
+    response_dict = {}  # TODO
+
+    with requests_mock.Mocker() as request_mock:
+        request_mock.post('https://example.com/reach', json=response_dict, status_code=200)
+        response = reach_client.try_send_sms(to, content, reference, False, 'sender')
+
+    # response_json = response.json()
+    assert response.status_code == 200
+    # TODO: assertions
+
+
+def test_try_send_sms_calls_reach_correctly(notify_api, mocker):
+    to = '+447234567890'
+    content = 'my message'
+    reference = 'my reference'
+    response_dict = {}  # TODO
+
+    with requests_mock.Mocker() as request_mock:
+        request_mock.post('https://example.com/reach', json=response_dict, status_code=200)
+        reach_client.try_send_sms(to, content, reference, False, 'sender')
+
+    assert request_mock.call_count == 1
+    assert request_mock.request_history[0].url == 'https://example.com/reach'
+    assert request_mock.request_history[0].method == 'POST'
+
+    # request_args = request_mock.request_history[0].json()
+    # TODO: assertions
+
+
+def test_try_send_sms_raises_if_reach_rejects(notify_api, mocker):
+    to = content = reference = 'foo'
+    response_dict = {
+        'Error': 206,
+        'Description': 'Some kind of error'
+    }
+
+    with pytest.raises(SmsClientResponseException) as exc, requests_mock.Mocker() as request_mock:
+        request_mock.post('https://example.com/reach', json=response_dict, status_code=400)
+        reach_client.try_send_sms(to, content, reference, False, 'sender')
+
+    assert exc.value.status_code == 400
+    assert '"Error": 206' in exc.value.text
+    assert '"Description": "Some kind of error"' in exc.value.text
+    assert type(exc.value.exception) == HTTPError
+
+
+def test_try_send_sms_raises_if_reach_fails_to_return_json(notify_api, mocker):
+    to = content = reference = 'foo'
+    response_dict = 'NOT AT ALL VALID JSON {"key" : "value"}}'
+
+    with pytest.raises(SmsClientResponseException) as exc, requests_mock.Mocker() as request_mock:
+        request_mock.post('https://example.com/reach', text=response_dict, status_code=200)
+        reach_client.try_send_sms(to, content, reference, False, 'sender')
+
+    assert 'Code 200 text NOT AT ALL VALID JSON {"key" : "value"}} exception Expecting value: line 1 column 1 (char 0)' in str(exc.value)  # noqa
+    assert exc.value.status_code == 200
+    assert exc.value.text == 'NOT AT ALL VALID JSON {"key" : "value"}}'
+
+
+def test_try_send_sms_raises_if_reach_rejects_with_connect_timeout(rmock):
+    to = content = reference = 'foo'
+
+    with pytest.raises(ReachClientResponseException) as exc:
+        rmock.register_uri('POST', 'https://example.com/reach', exc=ConnectTimeout)
+        reach_client.try_send_sms(to, content, reference, False, 'sender')
+
+    assert exc.value.status_code == 504
+    assert exc.value.text == 'Gateway Time-out'
+
+
+def test_try_send_sms_raises_if_reach_rejects_with_read_timeout(rmock):
+    to = content = reference = 'foo'
+
+    with pytest.raises(ReachClientResponseException) as exc:
+        rmock.register_uri('POST', 'https://example.com/reach', exc=ReadTimeout)
+        reach_client.try_send_sms(to, content, reference, False, 'sender')
+
+    assert exc.value.status_code == 504
+    assert exc.value.text == 'Gateway Time-out'