SeeAllData = Fail

According to Auntie Pat Tern, it takes 21 days to break a bad habit, but Salesforce developers have had about that many API versions to break the bad habit of writing unit tests with "SeeAllData=true".

In most cases, this clause alone can render tests completely useless. Unit tests should prove that code functions according to specifications by asserting proper database manipulations--create, read, update, delete operations--as well as Visualforce navigation.

I looked at unit tests in my org and found this example of a test that failed to achieve its purpose:

This test should be asserting that the data for ordering samples can be created with just a contact and sample type defined.  Unfortunately the test relies on existing, live, org data rather than test 'silo' data because of "SeeAllData=true" in the first line. There are easy methods for unit tests to create their own test data without relying on live org data.

We encountered the following problems because of using "SeeAllData=true":

• It required us to maintain test data among our real data.
• When the test data was changed during data cleanup (in one case, Pat Tern's Account was deleted), the tests failed even though functionality was unchanged.
• Tests were not reliable between Sandboxes and Production orgs due to data differences rather than actual functionality.
• Apex Hammer Tests may not have been automatically monitored in our org for each Salesforce release since Hammer Tests are blind to live org data.

In the rare case where a specific piece of data may be required for your code to behave, consider using custom metadata types instead of Salesforce objects. Trailhead can help you learn more about how they allow you to move metadata and records between orgs and test functionality without needing to see all data in the org.