Add variant support

NEWS.md

@@ -1,5 +1,8 @@
 # vdiffr (development version)
 
+* Added support for snapshot variants (#125).
+
+
 # vdiffr 1.0.7
 
 * Revert back to C++11 to work around a GCC issue (#137).
@@ -95,7 +98,7 @@ a bugfix.
   Font sizes are now precomputed for the first 50000 unicode points.
   This allows deterministic computation of text box extents without
   the freetype and harfbuzz dependencies.
-  
+
   Note: The main visible change of this update is that points now look
   smaller. Points generated with the previous SVG engine were too large.
 

R/expect-doppelganger.R

@@ -54,6 +54,7 @@
 #'   Internally, this argument is passed to
 #'   [testthat::expect_snapshot_file()].
 #'
+#' @inheritParams testthat::expect_snapshot_file
 #'
 #' @section Debugging:
 #' It is sometimes difficult to understand the cause of a failure.
@@ -96,7 +97,8 @@ expect_doppelganger <- function(title,
                                 path = deprecated(),
                                 ...,
                                 writer = write_svg,
-                                cran = FALSE) {
+                                cran = FALSE,
+                                variant = NULL) {
   testthat::local_edition(3)
 
   fig_name <- str_standardise(title)
@@ -135,6 +137,7 @@ expect_doppelganger <- function(title,
       testcase,
       name = file,
       cran = cran,
+      variant = variant,
       compare = testthat::compare_file_text
     ),
     expectation_failure = function(cnd) {

tests/testthat/test-expect-doppelganger.R

@@ -82,3 +82,10 @@ test_that("skips and unexpected errors reset snapshots (r-lib/testthat#1393)", {
   expect_true(file.exists("test-snapshot/_snaps/snapshot/error-resets-snapshots.svg"))
   expect_true(file.exists("test-snapshot/_snaps/snapshot/skip-resets-snapshots.svg"))
 })
+
+test_that("`expect_doppelganger()` supports variants", {
+  p1 <- ggplot2::ggplot()
+  p2 <- ggplot2::ggplot() + ggplot2::geom_histogram()
+  expect_doppelganger("variant", p1, variant = "foo")
+  expect_doppelganger("variant", p2, variant = "bar")
+})