Scheduler: fix jest timezones (#30526)

Co-authored-by: Vladimir Bushmanov <[email protected]>
Co-authored-by: wdevfx <[email protected]>

Author: Ambrozy

packages/devextreme/js/__internal/scheduler/__tests__/performance.test.ts

@@ -34,6 +34,7 @@ describe('scheduler', () => {
       height: 600,
     });
     await timezoneUtils.cacheTimeZones();
+    timezoneUtils.getMachineTimezoneName();
 
     expect(container.classList).toContain('dx-scheduler');
 
@@ -46,6 +47,6 @@ describe('scheduler', () => {
     nextButton.click();
     expect(navigator.querySelector('.dx-scheduler-navigator-caption')?.textContent).toBe('20-26 January 2025');
 
-    expect(Intl.DateTimeFormat).toHaveBeenCalledTimes(timeZone ? 0 : 1);
+    expect(Intl.DateTimeFormat).toHaveBeenCalledTimes(0);
   });
 });

packages/devextreme/js/__internal/scheduler/workspaces/view_model/utils/view_generator_utils.test.ts

@@ -1,3 +1,11 @@
+/**
+ * @timezone Etc/GMT-2
+ */
+// NOTE: We use this utils for calculating weeks count in month view
+// The Scheduler cells already converted to "grid time" format
+// That's why we use locale (machine timezone) dependent dates here
+// Plus set specific timezone for test run
+
 import { describe, expect } from '@jest/globals';
 import each from 'jest-each';
 

packages/devextreme/jsdom-with-timezone.js

@@ -3,7 +3,10 @@ const JSDOMEnvironment = require('jest-environment-jsdom').TestEnvironment;
 module.exports = class TimezoneAwareJSDOMEnvironment extends JSDOMEnvironment {
     constructor(config, context) {
         // eslint-disable-next-line spellcheck/spell-checker
-        process.env.TZ = context.docblockPragmas.timezone || process.env.TZ || 'UTC';
+        const { timezone } = context.docblockPragmas;
+        if(timezone) {
+            process.env.TZ = timezone;
+        }
 
         super(config, context);
     }