Made S3 client injectable to ease mocking for testing

lolafect/lolaconfig.py

@@ -62,17 +62,21 @@ class LolaConfig:
             DEFAULT_KUBERNETES_IMAGE if kubernetes_image is None else kubernetes_image
         )
 
-    def fetch_slack_webhooks(self) -> None:
+    def fetch_slack_webhooks(self, s3_client=None) -> None:
         """
         Read the slack webhooks file from S3 and store the webhooks in memory.
 
+        :param s3_client: a client to fetch files from S3.
         :return: None
         """
+
+        if s3_client is None:
+            s3_client = boto3.client("s3")
+
         self.SLACK_WEBHOOKS = json.loads(
-            boto3.client("s3")
-            .get_object(Bucket=self.S3_BUCKET_NAME, Key=self.SLACK_WEBHOOKS_FILE)[
-                "Body"
-            ]
+            s3_client.get_object(
+                Bucket=self.S3_BUCKET_NAME, Key=self.SLACK_WEBHOOKS_FILE
+            )["Body"]
             .read()
             .decode("utf-8")
         )