Looking for logging into the Salesforce Test Script site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the Salesforce Test Script site. After that you can login as usual with your login credentials.
https://developer.salesforce.com/forums/?id=906F000000090mMIAQ
https://developer.salesforce.com/page/Basic_Apex_Code_Script
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_interface_System_SandboxPostCopy.htm
https://developer.salesforce.com/docs/atlas.en-us.api.meta/api/sforce_api_calls_login.htm
https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_testing_unit_tests_running.htm
https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/apex_uninstall_script_create.htm
https://trailhead.salesforce.com/en/content/learn/modules/identity_login/identity_login_my_domain
https://help.salesforce.com/apex/HTViewHelpDoc?id=code_test_execution.htm
https://trailhead.salesforce.com/content/learn/modules/modern-javascript-development/test-your-javascript
https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/apex_post_install_script_create.htm
https://success.salesforce.com/answers?id=9063A000000pT2wQAE
https://help.salesforce.com/articleView?id=trialforce_login_domain.htm&type=0
https://developer.salesforce.com/docs/atlas.en-us.packagingGuide.meta/packagingGuide/apex_post_install_script.htm