How to pass system variable or package option to tests with testthat

Introduction

In this article, we’ll explore how to pass system variables and package options to tests using the testthat package in R. We’ll delve into the specifics of how testthat works and provide practical examples of how to use it effectively.

Background

testthat is a popular testing framework for R that provides an easy-to-use interface for writing unit tests, integration tests, and other types of tests. One of its key features is the ability to run tests in a controlled environment, which can be useful for testing packages that rely on external dependencies or system variables.

When running tests with testthat, the test framework creates a temporary working directory and loads the package being tested into this directory. The package’s namespace is also loaded, allowing you to access its functions and data structures during the test run.

The Problem

In the question posed by the user, we see that some of the functionality used within tests requires setting system variables or package options beforehand. However, when using testthat, these settings are not propagated to subsequent tests, causing issues when trying to access the environment variables or package options within the test code.

Solution Overview

To solve this problem, we need to understand how testthat works and find a way to pass system variables or package options to tests in a controlled manner. One approach is to use the testthat::test_dir() function to create a temporary working directory for the test run, which allows us to set environment variables or package options before running each individual test.

Setting System Variables

To set system variables in a way that they are available to all tests, we can use the Sys.setenv() function before running each test. However, this approach requires modifying the test code for each individual test case.

A better approach is to create a temporary working directory using testthat::test_dir(), which allows us to set environment variables or package options within that directory. We can then run each individual test within this temporary directory, ensuring that the desired settings are available to all tests.

Here’s an example of how we can use testthat::test_dir() to pass system variables to tests:

library(testthat)
library(MyPackage)

# Create a temporary working directory for the test run
test_dir <- test_dir()

# Set environment variables or package options within the temporary directory
Sys.setenv("test123" = "test")

We can then use the test_dir() function to create a new working directory and set our desired settings. The test_dir() function will automatically load the package namespace and ensure that our tests run in an isolated environment.

Package Options

Passing package options is similar to setting system variables, but we need to specify the option name using the Option parameter of the Sys.setenv() function.

Here’s an example of how we can pass a package option to a test:

library(testthat)
library(MyPackage)

# Create a temporary working directory for the test run
test_dir <- test_dir()

# Set a package option within the temporary directory
options("MyOption" = "myvalue")

# Run each individual test within this temporary directory
testthat::test_file("tests/testAddOne.R")

In this example, we’re setting a package option called MyOption with the value "myvalue" using the options() function. We can then run each individual test within the temporary working directory, ensuring that our desired settings are available.

Example Use Case

To illustrate how to use these techniques, let’s create an example package addOne with a simple test suite:

# tests/testthat.R
library(testthat)
library(addOne)

Sys.setenv("test123" = "test")

test_check("addOne")

# tests/testAddOne.R
library(addOne)

stopifnot(identical(Sys.getenv("test123"), "test"))
test_that("zzz", expect_identical(Sys.getenv("test123"), "test"))

# tests/testAddOne_2.R
library(addOne)

options("MyOption" = "myvalue")

stopifnot(identical(options("MyOption"), "myvalue"))
test_that("ttt", expect_equal(options("MyOption"), "myvalue"))

In this example, we’re setting two environment variables and a package option using the Sys.setenv() and options() functions. We can then run each individual test within the temporary working directory, ensuring that our desired settings are available.

Conclusion

Passing system variables or package options to tests using testthat requires some creative thinking about how to structure your test code. By using the test_dir() function and setting environment variables or package options within a temporary working directory, we can ensure that our tests run in an isolated environment with the desired settings.

We hope this article has provided you with practical examples of how to use these techniques to improve the reliability and reproducibility of your R packages.

Last modified on 2024-09-16