Add a function to check if the test database is being used

This helps avoid problems when running the tests, and the test database not
being used.

guix-data-service/database.scm

@@ -17,10 +17,13 @@
 
 (define-module (guix-data-service database)
   #:use-module (system foreign)
+  #:use-module (ice-9 match)
   #:use-module (squee)
   #:export (with-postgresql-connection
             with-postgresql-transaction
 
+            check-test-database!
+
             with-advisory-session-lock
             obtain-advisory-transaction-lock
 
@@ -63,6 +66,12 @@
     (lambda (key . args)
       (exec-query conn "ROLLBACK;"))))
 
+(define (check-test-database! conn)
+  (match (exec-query conn "SELECT current_database()")
+    (((name))
+     (unless (string=? name "guix_data_service_test")
+       (error "tests being run against non test database")))))
+
 (define (with-advisory-session-lock conn lock f)
   (let ((lock-number (number->string (symbol-hash lock))))
     (exec-query conn