Create boilerplate test files from source files in an R package

use_tests.R

library(conflicted)
library(tidyverse)

new_region <- function(name) {
  paste0("# ", name, " ", strrep("-", max(88 - nchar(name) - 4, 0)))
}

boilerplate <- function(name) {
  paste(collapse = "\n", c(
    new_region(name),
    "",
    paste0('test_that("`', name, '()` snapshot test", {'),
    "  expect_snapshot({",
    paste0("    ", gsub("[.][^.]+$", "", name), "()"),
    "  })",
    "})"
  ))
}

sync_file <- function(path) {
  basename <- fs::path_file(path)
  test_path <- fs::path("tests/testthat", paste0("test-", basename))
  
  text <- brio::read_lines(path)
  
  matches <- str_match(text, "^([^ ]*) [<]- function[(]")
  functions <- unique(na.omit(matches[,2]))

  if (!fs::file_exists(test_path)) {
    old_tests <- NULL
  } else {
    old_tests <- paste(collapse = "\n", c(
      new_region("Legacy tests"),
      "",
      brio::read_lines(test_path)
    ))
  }
  
  code <- paste(c(map_chr(functions, boilerplate), old_tests), collapse = "\n\n\n")

  brio::write_lines(code, test_path)
}

files <- fs::dir_ls("R")

walk(files, sync_file)