call validate_config from after_initialize

lib/diaspora_federation.rb

@@ -34,12 +34,12 @@ module DiasporaFederation
     #   end
     def configure
       yield self
-      validate_config
-      logger.info "successfully configured the federation engine"
     end
 
-    private
-
+    ##
+    # validates if the engine is configured correctly
+    #
+    # called from after_initialize
     def validate_config
       raise ConfigurationError, "missing server_uri" unless @server_uri.respond_to? :host
       validate_class(@person_class, "person_class", %i(
@@ -53,8 +53,11 @@ module DiasporaFederation
         profile_url
         hcard_url
       ))
+      logger.info "successfully configured the federation engine"
     end
 
+    private
+
     def validate_class(klass, name, methods)
       raise ConfigurationError, "missing #{name}" unless klass
       const = const_get(klass)

lib/diaspora_federation/engine.rb

@@ -7,5 +7,9 @@ module DiasporaFederation
     config.generators do |g|
       g.test_framework :rspec
     end
+
+    config.after_initialize do
+      DiasporaFederation.validate_config
+    end
   end
 end