refactor test using new TaskSurv function

tests/testthat/test_partition.R

@@ -1,17 +1,18 @@
 test_that("partition w/ stratification works", {
-  task = tsk("rats")
-  sets = partition(task)
+  with_seed(42, {
+    task = tsk("rats")
+    part = partition(task, ratio = 0.8)
 
-  ratio = function(status) {
-    tab = table(status)
-    unname(tab[1L] / tab[2L])
-  }
+    ratio = function(status) {
+      tab = table(status)
+      unname(tab[1L] / tab[2L])
+    }
 
-  all = ratio(task$status())
-  train = ratio(task$status(sets$train))
-  test = ratio(task$status(sets$test))
+    all = task$cens_prop()
+    train = task$cens_prop(rows = part$train)
+    test = task$cens_prop(rows = part$test)
 
-  expect_numeric(all, lower = 6, upper = 6.2)
-  expect_numeric(train, lower = 6, upper = 6.2)
-  expect_numeric(test, lower = 6, upper = 6.2)
+    expect_equal(all, train, tolerance = 0.01)
+    expect_equal(all, test, tolerance = 0.01)
+  })
 })