WMDE\Fundraising\Frontend\Tests\EdgeToEdge\CampaignCookieTest can have failing test cases when the A/B test configuration of the production environment changes. Also it references the class WMDE\Fundraising\Frontend\Tests\Fixtures\FixedCampaignConfigurationLoader which does not exist.

Acceptance Criteria:

• Implement Fixture class WMDE\Fundraising\Frontend\Tests\Fixtures\FixedCampaignConfigurationLoader which returns a the configuration from the constructor when loadCampaignConfiguration is called.
• In CampaignCookieTest, replace instances of OverridingCampaignConfigurationLoader with FixedCampaignConfigurationLoader and use the TEST_CAMPAIGN_CONFIG as the configuration in all test cases.