add test to ensure pruning cache by number of files sorts by key if necessary

Author: Stefan Fleck

tests/testthat/test_Cache.R

@@ -8,7 +8,8 @@ context("Cache")
 assign("id", 0L, .id_cache)
 ascending_id <- function(){
   x <- get("id", .id_cache)
-  x <- as.character(as.integer(x) + 1L)
+  x <- pad_left(as.integer(x) + 1L, width = 8, pad = "0")
+  assert(identical(nchar(x), 8L))
   assign("id", x, .id_cache)
   x
 }
@@ -97,6 +98,30 @@ test_that("pruning works by number of files works", {
 
 
 
+test_that("pruning works by number of files sorts by key if timestamp are identical", {
+  td <- file.path(tempdir(), "cache-test")
+  on.exit(unlink(td, recursive = TRUE))
+
+  cache <- Cache$new(td, hashfun = function(x) ascending_id())
+  k1 <- cache$push(iris)
+  k2 <- cache$push(letters)
+  k3 <- cache$push(cars)
+  expect_identical(cache$n, 3L)
+
+  Sys.setFileTime(cache$files$path, "1999-01-01 00:00:00")
+
+  expect_identical(cache$files$key[[1]], k1)
+  expect_identical(cache$files$key[[2]], k2)
+  expect_identical(cache$files$key[[3]], k3)
+
+  cache$prune(max_files = 2)
+  expect_identical(cache$read(cache$files$key[[1]]), letters)
+  expect_identical(cache$read(cache$files$key[[2]]), cars)
+  cache$purge()
+})
+
+
+
 
 test_that("pruning by size works", {
   td <- file.path(tempdir(), "cache-test")