测试与R包中的用户的交互 [英] Test interaction with users in R package

问题描述

我正在开发一个R包，其中一个功能是通过readline通过标准输入实现与用户的交互.我现在想知道如何测试此功能的行为，最好使用testthat库.

I am developing an R package and one of the function implements interaction with users through standard input via readline. I now wonder how to test the behavior of this function, preferably with testthat library.

似乎test_that函数假定用户输入的答案是"".我希望我可以测试用户可以输入的各种答案的行为条件.

It seems test_that function assumes the answer is "" for user-input. I wish I could test the behavior conditional of various answers users may type in.

下面是一个小的示例代码.在实际的开发中，marryme函数是在单独的文件中定义的，并导出到名称空间. devtools::test()在最后一行给我一个错误，因为答案永远不会变成是.我想测试用户键入"y"时函数是否正确返回true.

Below is a small example code. In the actual development, the marryme function is defined in a separate file and exported to the namespace. devtools::test() gets me an error on the last line because the answer never becomes yes. I would like to test if the function correctly returns true when user types "y".

library(testthat)

test_that("input", {
  marryme <- function() {
    ans <- readline("will you marry me? (y/n) > ")
    return(ans == "y")
  }

  expect_false(marryme())  # this is good
  expect_true(marryme())   # this is no good
})

推荐答案

通过自定义连接使用readLines()

通过使用readLines()而不是readline()，您可以定义连接，从而可以使用全局选项自定义连接.

Use readLines() with a custom connection

By using readLines() instead of readline(), you can define the connection, which allows you to customize it using global options.

您需要执行两个步骤:

1. 在包中的zzz.R中设置一个默认选项，该选项指向stdin:

1. set a default option in your package in zzz.R that points to stdin:

.onAttach <- function(libname, pkgname){
  options(mypkg.connection = stdin())
}

在您的函数中，将readline更改为readLines(n = 1)并将readLines()中的连接设置为getOption("mypkg.connection")

In your function, change readline to readLines(n = 1) and set the connection in readLines() to getOption("mypkg.connection")

示例

基于您的MWE:

Example

Based on your MWE:

    library(testthat)

    options(mypkg.connection = stdin())

    marryme <- function() {
      cat("will you marry me? (y/n) > ")
      ans <- readLines(con = getOption("mypkg.connection"), n = 1)
      cat("\n")
      return(ans == "y")
    }

    test_that("input", {

      f <- file()
      options(mypkg.connection = f)
      ans <- paste(c("n", "y"), collapse = "\n") # set this to the number of tests you want to run
      write(ans, f)

      expect_false(marryme())  # this is good
      expect_true(marryme())   # this is no good
      # reset connection
      options(mypkg.connection = stdin())
      # close the file
      close(f)
    })
#> will you marry me? (y/n) > 
#> will you marry me? (y/n) >

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