Resolve "Workflow usage statistics"

Closes #24 (closed)

app/tests/api/test_workflow.py

+from datetime import date
 from io import BytesIO
 from uuid import UUID, uuid4
 
 import pytest
-from clowmdb.models import Workflow, WorkflowVersion
+from clowmdb.models import Workflow, WorkflowExecution, WorkflowVersion
 from fastapi import status
 from httpx import AsyncClient
 from sqlalchemy import delete, select
@@ -380,6 +381,34 @@ class TestWorkflowRoutesGet(_TestWorkflowRoutes):
         )
         assert response.status_code == status.HTTP_404_NOT_FOUND
 
+    @pytest.mark.asyncio
+    async def test_get_workflow_statistics(
+        self,
+        client: AsyncClient,
+        random_user: UserWithAuthHeader,
+        random_workflow: WorkflowOut,
+        random_workflow_execution: WorkflowExecution,
+    ) -> None:
+        """
+        Test for getting a non-existing workflow.
+
+        Parameters
+        ----------
+        client : httpx.AsyncClient
+            HTTP Client to perform the request on. pytest fixture.
+        random_user : app.tests.utils.user.UserWithAuthHeader
+            Random user for testing. pytest fixture.
+        """
+        response = await client.get(
+            "/".join([self.base_path, str(random_workflow.workflow_id), "statistics"]),
+            headers=random_user.auth_headers,
+        )
+        assert response.status_code == status.HTTP_200_OK
+        statistics = response.json()
+        assert len(statistics) == 1
+        assert statistics[0]["day"] == str(date.today())
+        assert statistics[0]["count"] == 1
+
 
 class TestWorkflowRoutesDelete(_TestWorkflowRoutes):
     @pytest.mark.asyncio