tests/testthat/setup_expect_snapshot_plot.R

In tmcd82070/Rdistance: Density and Abundance from Distance-Sampling Surveys

# Helper functions for plot snapshot testing.

save_png <- function(code, width = 400, height = 400) {
  path <- tempfile(fileext = ".png")
  png(path, width = width, height = height)
  on.exit(dev.off())
  code
  
  path
}

expect_snapshot_plot <- function(name, code) {
  # Other packages might affect results
  # skip_if_not_installed("ggplot2", "2.0.0")
  # Or maybe the output is different on some operation systems
  # skip_on_os("windows")
  # You'll need to carefully think about and experiment with these skips
  
  name <- paste0(name, ".png")
  
  # Announce the file before touching `code`. This way, if `code`
  # unexpectedly fails or skips, testthat will not auto-delete the
  # corresponding snapshot file.
  announce_snapshot_file(name = name)
  
  path <- save_png(code)
  expect_snapshot_file(path, name)
}