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Run Specified Tests - This option allows you to determine which tests you specifically want to run. This is great for deployments to staging sandboxes and provides you with the most control possible.
Run Local Tests - This option will run all tests in your organization except ones that originate from installed managed packages. This test level is the default for production deployments that include Apex classes or triggers. This is a great option to run tests that you’ve written, and which are under your control but ignoring those that may come with managed packages or installed apps. It can be a big time and frustration saver.
Run All Tests in Org - This option runs all tests in your Salesforce org, including third-party tests from managed packages.
Specified and Package Tests - This is an additional test level provided by FlexDeploy. It automatically selects all test classes available in the package and allows the user to further refine the selection by adding or removing test classes. This option provides flexibility and control, ensuring comprehensive testing of package-related changes while allowing for customization based on specific needs. By automatically selecting all test classes in the package, it saves time and ensures that no relevant tests are missed.
Reference screenshot is here .-
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