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alexford/faketime_rspec.md

Created April 1, 2019 19:23
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Freeze system time for Ruby/RSpec
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faketime_rspec.md

Assumptions

  • macOS 10.14
  • rbenv
  • Homebrew

Steps

Install libfaketime

https://github.com/wolfcw/libfaketime

brew install libfaketime

Set environment variables

export DYLD_FORCE_FLAT_NAMESPACE=1
export DYLD_INSERT_LIBRARIES=/usr/local/Cellar/libfaketime/0.9.7_1/lib/faketime/libfaketime.1.dylib

(The path to the library might change depending on the version)

Run ruby with rbenv which

(You cannot go through the ruby shim rbenv provides, the executable must be called directly)

With ruby -e

$ FAKETIME="@2020-12-24 20:30:00" `rbenv which ruby` -e "puts Time.now"
2020-12-24 20:30:00 -0500

With irb

$ FAKETIME="@2020-12-24 20:30:00" `rbenv which irb`
irb(main):001:0> Time.now
=> 2020-12-24 20:30:02 -0500

With Rspec

$ FAKETIME="@2020-12-24 20:30:00" `rbenv which rspec` spec/services/generate_benefits_summary_spec.rb
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