Test if the new plot matches a target (snapshot) plot — expect_snapshot

This expectation can be used with tinytest to check if the new plot matches a target plot.

When the expectation is checked for the first time, the expectation fails and a reference plot is saved to the inst/tinytest/_tinysnapshot folder.

When the expectation fails, the reference plot, the new plot, and a diff are saved to the inst/tinytest/label folder. Call the review() function to compare.

To update a snapshot, delete the reference file from the _tinysnapshot folder and run the test suite again.

See the package README file or website for detailed examples.

Usage

expect_snapshot_plot(
  current,
  label,
  width = getOption("tinysnapshot_width", default = NULL),
  height = getOption("tinysnapshot_height", default = NULL),
  tol = getOption("tinysnapshot_tol", default = 0),
  metric = getOption("tinysnapshot_metric", default = "AE"),
  fuzz = getOption("tinysnapshot_fuzz", default = 0),
  device = getOption("tinysnapshot_device", default = "svg"),
  device_args = getOption("tinysnapshot_device_args", default = list()),
  par_args = getOption("tinysnapshot_par_args", default = NULL),
  style = getOption("tinysnapshot_plot_diff_style", default = c("old", "new", "diff")),
  review = getOption("tinysnapshot_plot_review", default = TRUE),
  os = getOption("tinysnapshot_os", default = Sys.info()["sysname"]),
  skip = getOption("tinysnapshot_plot_skip", default = !interactive() &&
    !identical(Sys.getenv("NOT_CRAN"), "true"))
)

Arguments

current: an object of class ggplot or a function which returns a base R plot.
label: a string to identify the snapshot (alpha-numeric, hyphens, or underscores). Each plot in the test suite must have a unique label.
width: of the snapshot. PNG default: 480 pixels. SVG default: 7 inches.
height: of the snapshot. PNG default: 480 pixels. SVG default: 7 inches.
tol: distance estimates larger than this threshold will trigger a test failure. Scale depends on the metric argument. With the default metric="AE" (absolute error), the tolerance corresponds roughly to the number of pixels of difference between the plot and the reference image.
metric: string with a metric from magick::metric_types() such as "AE" or "phash".
fuzz: relative color distance between 0 and 100 to be considered similar.
device: "svg", "png", "ragg" or "svglite"
device_args: list of arguments to pass to the device call (e.g., user_fonts for svglite device).
par_args: named list of arguments to pass to graphics::par() for setting graphical parameters. Only used when device is "png" or "ragg". Default is NULL.
style: A character vector to control the panels of the diff image saved to file. The order and number of entries controls the side-by-side panels. Allowable values are: "old", "new", "diff".
review: logical. TRUE if a a diff plot should be saved to file for review when the expectation fails.
os: character vector of operating systems on which the test should be run (e.g., "Windows", "Linux", "Darwin"). Tests are skipped when no element of the vector matches the output of: Sys.info()["sysname"]
skip: logical. If TRUE, the test is skipped. Default: TRUE when not interactive and NOT_CRAN environment variable is not "true".

Value

A tinytest object. A tinytest object is a logical with attributes holding information about the test that was run