Add initial API tests

Test the basic assumptions of the API like response codes and types.

tests/test_api.py

@@ -0,0 +1,67 @@
+from falcon import testing
+import json
+import pytest
+
+from dspace_statistics_api.app import api
+
+
+@pytest.fixture
+def client():
+    return testing.TestClient(api)
+
+
+def test_get_docs(client):
+    '''Test requesting the documentation at the root.'''
+
+    response = client.simulate_get('/')
+
+    assert isinstance(response.content, bytes)
+    assert response.status_code == 200
+
+
+def test_get_item(client):
+    '''Test requesting a single item.'''
+
+    response = client.simulate_get('/item/17')
+    response_doc = json.loads(response.content)
+
+    assert isinstance(response_doc['downloads'], int)
+    assert isinstance(response_doc['id'], int)
+    assert isinstance(response_doc['views'], int)
+    assert response.status_code == 200
+
+
+def test_get_missing_item(client):
+    '''Test requesting a single non-existing item.'''
+
+    response = client.simulate_get('/item/1')
+
+    assert response.status_code == 404
+
+
+def test_get_items(client):
+    '''Test requesting 100 items.'''
+
+    response = client.simulate_get('/items', query_string='limit=100')
+    response_doc = json.loads(response.content)
+
+    assert isinstance(response_doc['currentPage'], int)
+    assert isinstance(response_doc['totalPages'], int)
+    assert isinstance(response_doc['statistics'], list)
+    assert response.status_code == 200
+
+
+def test_get_items_invalid_limit(client):
+    '''Test requesting 100 items with an invalid limit parameter.'''
+
+    response = client.simulate_get('/items', query_string='limit=101')
+
+    assert response.status_code == 400
+
+
+def test_get_items_invalid_page(client):
+    '''Test requesting 100 items with an invalid page parameter.'''
+
+    response = client.simulate_get('/items', query_string='page=-1')
+
+    assert response.status_code == 400