Add tests for get_complaint_count endpoint

* Added unit tests for the get_complaint_count endpoint
* Updated the schema to use 'date' format instead of 'datetime'
* Updated the complaint endpoint to convert start_date and end_date to
be dates instead of strings

tests/app/complaint/test_complaint_rest.py

@@ -1,5 +1,9 @@
+from datetime import date
 import json
 
+from flask import url_for
+from freezegun import freeze_time
+
 from tests import create_authorization_header
 from tests.app.db import create_complaint, create_service, create_template, create_notification
 
@@ -22,3 +26,39 @@ def test_get_all_complaints_returns_empty_list(client):
 
     assert response.status_code == 200
     assert json.loads(response.get_data(as_text=True)) == []
+
+
+def test_get_complaint_with_start_and_end_date_passes_these_to_dao_function(mocker, client):
+    start_date = date(2018, 6, 11)
+    end_date = date(2018, 6, 11)
+    dao_mock = mocker.patch('app.complaint.complaint_rest.fetch_count_of_complaints', return_value=3)
+    response = client.get(
+        url_for('complaint.get_complaint_count', start_date=start_date, end_date=end_date),
+        headers=[create_authorization_header()]
+    )
+
+    dao_mock.assert_called_once_with(start_date=start_date, end_date=end_date)
+    assert response.status_code == 200
+    assert json.loads(response.get_data(as_text=True)) == 3
+
+
+@freeze_time("2018-06-01 11:00:00")
+def test_get_complaint_sets_start_and_end_date_to_today_if_not_specified(mocker, client):
+    dao_mock = mocker.patch('app.complaint.complaint_rest.fetch_count_of_complaints', return_value=5)
+    response = client.get(url_for('complaint.get_complaint_count'), headers=[create_authorization_header()])
+
+    dao_mock.assert_called_once_with(start_date=date.today(), end_date=date.today())
+    assert response.status_code == 200
+    assert json.loads(response.get_data(as_text=True)) == 5
+
+
+def test_get_complaint_with_invalid_data_returns_400_status_code(client):
+    start_date = '1234-56-78'
+    response = client.get(
+        url_for('complaint.get_complaint_count', start_date=start_date),
+        headers=[create_authorization_header()]
+    )
+
+    assert response.status_code == 400
+    assert response.json['errors'][0]['message'] == 'start_date time data {} does not match format %Y-%m-%d'.format(
+        start_date)