expect_snapshot_plot {tinysnapshot}

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

Description

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()),
  os = getOption("tinysnapshot_os", default = Sys.info()["sysname"])
)

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).

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"]

Value

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