TL;DR In blueprints, always wrap associations in blocks.

# Broken
Task.blueprint(:vacation) do
  project Project.make(:vacation)
  hours 8
  accounting_method 'none'
end

# Correct
Task.blueprint(:vacation) do
  project { Project.make(:vacation) }
  hours 8
  accounting_method 'none'
end

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Without the block, Project.make will only run once when the blueprint is parsed (usually when RSpec is loaded), which is not what you want.