maint: Maintain own test setup config.

Don't extend from @patternslib/patternslib for setting up tests.
The config files are not included in the npm package distributions anymore.

jest.config.js

@@ -1,5 +1,5 @@
 const path = require("path");
-const config = require("@patternslib/patternslib/jest.config.js");
+const config = require("@patternslib/dev/jest.config.js");
 
 config.setupFilesAfterEnv.push(path.resolve(__dirname, "./src/setup-tests.js"));
 

src/setup-tests.js

@@ -0,0 +1,21 @@
+// Extra test setup.
+
+import jquery from "jquery";
+global.$ = global.jQuery = jquery;
+
+jquery.expr.pseudos.visible = function () {
+    // Fix jQuery ":visible" selector always returns false in JSDOM.
+    // https://github.com/jsdom/jsdom/issues/1048#issuecomment-401599392
+    return true;
+};
+
+// Do not output error messages
+import logging from "@patternslib/patternslib/core/logging";
+logging.setLevel(50);
+// level: FATAL
+
+// patch dom.is_visible to not rely on jest-unavailable offsetWidth/Height
+import dom from "@patternslib/patternslib/core/dom";
+dom.is_visible = (el) => {
+    return !el.hidden && el.style.display !== "none";
+};