Add svmPoly test for ordering of facets' labels

pkg/caret/tests/testthat/test_ggplot.R

@@ -1,12 +1,16 @@
 context("Test ggplot")
 
 test_that("ggplot.train correctly orders factors", {
+  library(caret)
+  library(kernlab)
   data(mtcars)
-  m <- train(mpg ~ cyl + disp,
-             data = mtcars,
-             method="svmRadial",
-             tuneGrid = expand.grid(C=1:2, sigma=c(0.0001, 0.01, 1)))
-  g <- ggplot(m, plotType="level")
+  m <- train(
+    mpg ~ cyl + disp,
+    data = mtcars,
+    method = "svmRadial",
+    tuneGrid = expand.grid(C = 1:2, sigma = c(0.0001, 0.01, 1))
+  )
+  g <- ggplot(m, plotType = "level")
 
   # Test plot data
   obj_sigma <- as.numeric(levels(g$data$sigma))
@@ -21,3 +25,37 @@ test_that("ggplot.train correctly orders factors", {
   expect_equal(obj_x, sort(obj_x))
   expect_equal(obj_y, sort(obj_y))
 })
+
+test_that("ggplot.train correctly orders facets' labels", {
+  library(caret)
+  library(kernlab)
+  data(mtcars)
+  m <- suppressWarnings(train(
+    mpg ~ cyl + disp,
+    data = mtcars,
+    method = "svmPoly",
+    tuneGrid = expand.grid(
+      degree = c(0.0001, 0.01, 1),
+      scale = c(0.0001, 0.01, 1),
+      C = c(0.0001, 0.01, 1)
+    )
+  ))
+  g <- ggplot(m, plotType = "level", nameInStrip = TRUE)
+
+  # Test plot data
+  obj_C <- as.numeric(gsub(
+    'Cost: ',
+    '',
+    levels(g$data$C)
+  ))
+  expect_equal(obj_C, sort(obj_C))
+
+  # Test axes' labels on a built plot
+  build <- ggplot2::ggplot_build(g)
+  obj_labels <- as.numeric(gsub(
+    'Cost: ',
+    '',
+    levels(build$layout$panel_layout$C)
+  ))
+  expect_equal(obj_labels, sort(obj_labels))
+})