A developer creates a new Apex trigger with a helper class, and writes a test class that only exercises 95% coverage of new Apex helper class. Change Set deployment to production fails with the test…

Even if the helper class has high coverage, a trigger itself must have its execution paths invoked and covered by a test method. The error message explicitly states "Test coverage of selected Apex Trigger is 0%", meaning the test class isn't calling the trigger's logic, requiring specific test methods to create/update/delete records that fire the trigger.

Running all tests might help identify other issues but will not inherently add coverage to a specific trigger if no test methods are designed to invoke it.

Removing failing test methods would not address the 0% coverage on the trigger and is generally bad practice as it reduces test robustness.

While increasing helper class coverage is good practice, it does not directly address the 0% coverage requirement for the trigger itself, as the trigger must be invoked by test data to gain coverage.