By Ben Yu
Helper methods make it easier to create test data. But they can become difficult to read over time as you need more variations of the test data to satisfy constantly evolving requirements from new tests:
// This helper method starts with just a single parameter:
Instead, use the test data builder pattern: create a helper method that returns a partially-built object (e.g., a Builder in languages such as Java, or a mutable object) whose state can be overridden in tests. The helper method initializes logically-required fields to reasonable defaults, so each test can specify only fields relevant to the case being tested:
Company small = newCompany().setEmployees(2).setBoardMembers(2).build();
// Zero parameters makes this method reusable for different variations of Company.
Also note that tests should never rely on default values that are specified by a helper method since that forces readers to read the helper method’s implementation details in order to understand the test.
// This test needs a public company, so explicitly set it.
You can learn more about this topic at http://www.natpryce.com/articles/000714.html