Json-schema tests: add schema specifier to test

lib/jsonschema/example-schema.json

@@ -1,4 +1,5 @@
 {
+  "$schema": "http://json-schema.org/draft-07/schema#",
   "type": "object",
   "additionalProperties": false,
   "properties": {

lib/jsonschema/test_parseOptions.nix

@@ -4,16 +4,9 @@
   lib ? (import <nixpkgs> { }).lib,
   slib ? import ./. { inherit lib; },
 }:
-let
-  evaledOptions =
-    let
-      evaledConfig = lib.evalModules { modules = [ ./example-interface.nix ]; };
-    in
-    evaledConfig.options;
-in
 {
   testParseOptions = {
-    expr = slib.parseOptions evaledOptions;
+    expr = slib.parseModule ./example-interface.nix;
     expected = builtins.fromJSON (builtins.readFile ./example-schema.json);
   };