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A different way of looking at this is that by creating the helper classes, we are just abstracting out duplicate code from the unit test classes themselves. So perhaps the builders do belong in the test hierarchy. They are not strictly unit tests themselves, but by putting them under test, they would only be used when tests were run and would not be deployed as part of an app.
Core Data Factory Javadoc
Here's a screenshot showing the Javadoc for the Core Data Factory class. 