add nix flake check

Makefile

@@ -1,7 +1,14 @@
+# unit tests independent of your environment. Aspires to be the default CI job.
 .PHONY: check
 test:
-	nix build .#e11sync-gunicorn.tests.simple -L
+	nix flake check
 
+# Dev.
+.PHONY: run
+run:
+	app/manage.py runserver
+
+# "Like production". Run with "run-caddy".
 .PHONY: run-gunicorn
 run-gunicorn:
 	nix run .#e11sync-gunicorn

flake.nix

@@ -106,6 +106,8 @@
         };
       };
 
+      checks.e11sync = packages.e11sync-gunicorn.passthru.tests.simple;
+
       apps.e11sync-gunicorn = {
         type = "app";
         name = "e11sync-gunicorn";