Using `alike` with `ensurer`

ensure_alike.R

# Packages

library(devtools)
install_github("smbache/ensurer")
install_github("brodieg/alike")
library(ensurer)
library(alike)
library(magrittr)
set.seed(1)

# Objects to test

iris.tpl <- iris[0, ]
iris.2 <- iris.3 <- iris[sample(seq(len=nrow(iris)), 10), ]       # random subset of iris
levels(iris.3$Species) <- c(levels(iris.3$Species), "americana")  # add level to iris.3

# Template test 1 (from `ensurer` vignette)

ensure_as_template <- function(x, tpl)
  ensure_that(x,
    is.data.frame(.),
    identical(class(.), class(tpl)),
    identical(sapply(., class), sapply(tpl, class)),
    identical(sapply(., levels), sapply(tpl, levels))
  )

x.1 <- iris.2 %>% ensure_as_template(iris.tpl)    # pass
x.2 <- iris.3 %>% ensure_as_template(iris.tpl)    # fail

# Template test 2 (alike adaptation)

ensure_as_template2 <- function(x, tpl) 
  ensure_that(x, alike(tpl, .))

x.3 <- iris.2 %>% ensure_as_template2(iris.tpl)   # pass
x.4 <- iris.3 %>% ensure_as_template2(iris.tpl)   # fail
alike(iris.tpl, iris.3)                           # alike tells you why the structure is unequal
# [1] "Mismatch at column `Species`: length mismatch for attribute \"levels\": expected 3, but got 4"