Time travel to test time dependent code - a port of Ruby’s timecop

BEWARE: VERY ALPHA

Package API:

  • time_fuzz
  • TimeStackItem
  • Time

Features supported:

  • freeze: freeze time to a specific point

Hope to support soon:

  • travel: travel back to a specific point in time, but allow time to continue moving forward from there
  • scale: scale time by a given scaling factor that will cause time to move at an accelerated pace

Installation

remotes::install_github("ropenscilabs/timefuzz")
library("timefuzz")

freeze

freeze with a code block

library(timefuzz)
library(clock)
library(testthat)

book_due() is a toy function that tells us if a book is due

book_due <- function(due_date = Sys.Date() + 10) {
  sys_date() > due_date
}

Given the due date of 2020-07-31 the book is not due

expect_false(book_due()) # FALSE

Create a time_fuzz object

x <- time_fuzz$new()
x
#> <time_fuzz> 
#>   date:

Call freez(), passing the date you want to freeze time to, and then a code block to run in the context of that frozen time. Here we’ll freeze time to today + 450 days

x$freeze(Sys.Date() + 450, {
  expect_true(book_due())
})
#> [1] TRUE

book_due() results in TRUE now, whereas it was FALSE above in real time

freeze without a code block

x <- time_fuzz$new()
## set to today + 450 days
x$freeze(Sys.Date() + 450)

We’re in the freezed date. So any time based actions using the [clock][] package are now using your frozen time context.

sys_time()
#> [1] "2021-10-13 17:00:00 PDT"

call $unfreeze() to unfreeze

x$unfreeze()

now we’re back in current time

sys_time()
#> [1] "2020-07-21 17:18:32 PDT"

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