No, every logic does not need a test case. However, every business requirement should have at least one test case. The key is to prioritize the test cases based on the importance of the functionality to the business. For example, a login feature is likely more important than a cosmetic change to the UI. As a result, it is more important to have test cases that cover the login feature than to have test cases that cover the UI change. When prioritizing test cases, it is also important to consider the risk of the change. For example, a change to the checkout process is likely riskier than a change to the product detail page. As a result, it is more important to have test cases that cover the checkout process than to have test cases that cover the product detail page. In general, you should prioritize your test cases based on the importance of the functionality to the business and the risk of the change.