PowerShell/docs/testing-guidelines/PesterDoAndDont.md

Do

1. Name your files .tests.ps1
2. Keep tests simple
   1. Test only what you need
   2. Reduce dependencies
3. Be sure to tag your Describe blocks based on their purpose
   1. Tag CI indicates that it will be run as part of the continuous integration process. These should be unit test like, and generally take less than a second.
   2. Tag Feature indicates a higher level feature test (we will run these on a regular basis), for example, tests which go to remote resources, or test broader functionality
   3. Tag Scenario indicates tests of integration with other features (these will be run on a less regular basis and test even broader functionality than feature tests.
4. Make sure that Describe/Context/It descriptions are useful
   1. The error message should not be the place where you describe the test
5. Use Context to group tests
   1. Multiple Context blocks can help you group your test suite into logical sections
6. Use BeforeAll/AfterAll/BeforeEach/AfterEach instead of custom initiators
7. Prefer Try-Catch for expected errors and check $_.fullyQualifiedErrorId (don't use should throw)
8. Use -testcases when iterating over multiple It blocks
9. Use code coverage functionality where appropriate
10. Use Mock functionality when you don't have your entire environment
11. Avoid free code in a Describe block
    1. Use [Before|After][Each|All] see Free Code in a Describe block
12. Avoid creating or using test files outside of TESTDRIVE:
    1. TESTDRIVE: has automatic clean-up
13. Keep in mind that we are creating cross platform tests
    1. Avoid using the registry
    2. Avoid using COM
14. Avoid being too specific about the count of a resource as these can change platform to platform
    1. ex: checking for the count of loaded format files, check rather for format data for a specific type

Don't

1. Don't have too many evaluations in a single It block
   1. The first Should failure will stop that block
2. Don't use Should outside of an It Block
3. Don't use the word "Error" or "Fail" to test a positive case
   1. ex: "Get-Childitem TESTDRIVE: shouldn't fail", rather "Get-ChildItem should be able to retrieve file listing from TESTDRIVE"