检查一个函数是否在另一个函数内部被调用 [英] Check if a function is called inside another function

问题描述

假设我有这个功能

mean_wrapper <- function(x) {
  mean(x)
}

如何检查 mean 函数是否被调用?

How can I check if the mean function is called?

一个用例是例如如果我想在单元测试中检查这个行为.

An use case is for instance If I want to check this behavior in a unit test.

为了更清楚，我再举一个例子.让我们考虑这个函数:

I make another exampe to be clearer. Let consider this function:

library(readr)
library(magrittr)

read_data <- function(file_name) {
  read_csv(file_name) %>%
    validate_data()
}

read_data 的目的是读取 CVS 文件并对其进行验证.validate_data 对数据执行一些检查.如果其中一个失败，它会引发错误，否则返回输入对象.

The aim of read_data is to read a CVS file and validate it. validate_data performs some checks on the data. It raises an error if one of them fail, otherwise returns the input object.

我想测试这两个函数，但我不想在 read_data 的情况下复制我为 validate_data 编写的相同测试.无论如何，我必须检查后一个函数是否已在 read_data 中调用，因此我想编写一个测试来为我执行此操作.

I want to test both functions but I don't want replicate the same tests I wrote for validate_data in the case of read_data. Anyway I have to check that the latter function has been called in read_data, so I wolud like to write a test that does this for me.

推荐答案

You can trace mean:

You could trace mean:

trace(mean, tracer = quote(message("mean was called")))
mean_wrapper(3)
#Tracing mean(x) on entry 
#mean was called
#[1] 3
untrace(mean)
#Untracing function "mean" in package "base"

您可以使用任何东西(例如，对封闭环境中的变量进行赋值)来代替消息作为跟踪器.

Instead of a message you can use anything (e.g., assignment to a variable in the enclosing environment) as tracer.

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