optimize test fixtures

Use the fab! shorthand syntax for creating test fixtures and reuse fabricated objects across tests to improve performance and maintainability. The fab! method creates objects once per test context and reuses them, reducing database overhead compared to creating new objects for each test.

Preferred approach:

fab!(:theme_1, :theme)
fab!(:theme_2, :theme) 
fab!(:tag_1, :tag)
let(:tags) { [tag_1, tag_2, tag_3] }

Instead of:

fab!(:theme_1) { Fabricate(:theme) }
fab!(:theme_2) { Fabricate(:theme) }
let(:tags) { 3.times.collect { Fabricate(:tag) } }

When possible, reuse top-level fabricated objects in nested contexts rather than creating new ones. For example, use event = Fabricate(:event, post: admin_post) instead of post = Fabricate(:post, user: Fabricate(:admin)) when an admin_post fixture already exists at the top level. This approach reduces test setup time, improves readability, and makes test dependencies more explicit.