如果目录中没有文件，如何在testthat中写入expect_error以抛出错误？

Question

我是运行一个 R 代码，如果目录中没有文件，则使用 testthat 抛出错误。我的测试代码如下，（我根据Waldi的回答进行了编辑）

test_that(desc = "Test for 'LoadData' Condition 1",
          code = {
            filePath = "./UnitTest/Data/Expected_Output2"
            expect_error(LoadData(inputPath = filePath),"There's no file at ./UnitTest/Data/Expected_Output2")
          }
)

我的职能是，

LoadData = function(inputPath) {
if(!file.exists(inputPath){
 stop(paste0("There's no file at ", inputPath))
   }
}

我的测试代码失败并显示此消息，

Error: `LoadData(inputPath = filePath)` threw an error with unexpected message.
Expected match: "There's no file at ./UnitTest/Data/Expected_Output_2"
Actual message: "cannot open the connection"
In addition: Warning message:
In open.connection(con, "rb") :
  cannot open file './UnitTest/Data/Expected_Output_2': Permission denied

Answer 1

您只需准确测试预期的错误消息即可：

library(testthat)


LoadData = function(inputPath) {
  if(length(list.files(inputPath))==0){
    stop(paste0("There's no file at ", inputPath))
  }
}


test_that(desc = "Test for 'LoadData' Condition 1",
          code = {
            filePath = "./UnitTest/Data/Expected_Output2"
            expect_error(LoadData(inputPath = filePath),"There's no file at ./UnitTest/Data/Expected_Output2")
          }
)

^{由 reprex package (v0.3.0)}

于 2020-07-06 创建

以上测试成功，因为结果为：

    LoadData("./UnitTest/Data/Expected_Output2")

出现以下错误：

Error in LoadData("./UnitTest/Data/Expected_Output2") : 
  There's no file at ./UnitTest/Data/Expected_Output2

Answer 2

解决此问题的一种方法是分配一个 json 文件，该文件实际上不存在于目录中，如下所示：

test_that(desc = "Test for 'LoadData' Condition 1",
          code = {
            filePath = "./UnitTest/Data/Expected_Output2/nofiles.json"
            expect_error(LoadData(inputPath = filePath),"There's no file at ./UnitTest/Data/Expected_Output2/nofiles.json")
          }
)

这里我们需要注意理解，之前我们只是分配了一个空路径。但是我们需要分配一个实际上不存在的假设文件。这对我有用。我的测试成功了。

如果目录中没有文件，如何在testthat中写入expect_error以抛出错误？

how to write expect_error in testthat to throw an error if there is no file in the directory?

testing

unit-testing

r

testthat