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xpectr

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xpectr provides a set of utilities and RStudio addins for generating tests for testthat unit testing.

Author: Ludvig R. Olsen ( r-pkgs@ludvigolsen.dk )
Started: January 2020

Lifecycle: experimental

When developing R packages, it’s good practice to build a good set of unit tests that will notify you when something breaks in the future. For this, the testthat package is commonly used. Often though, we end up writing a similar set of tests again and again, which can be both tedious and time-consuming.

xpectr helps you by generating common testthat tests. Its goal is not to replace the active thinking process of finding meaningful tests for your functions, but to help systematize and ease that process.

One such example is gxs_function(), which generates tests for a set of argument value combinations. This allows you to focus on the selection of argument values to test. Once the tests have been generated, you can go through each of them to ensure your function is working as intended and to add relevant tests.

Note: If you comment out the call to gxs_function(), it is easy to later regenerate the tests. By using a diff tool, you can check that only the intended changes have been made to the file.

Call for feedback

While xpectr has already shown itself very useful in the scenarios I’ve used it in, its usefulness is likely to multiply with the amount of feedback by the community of package developers.

If you have any thoughts on the current set of tests and supported objects, or ideas for improvements/additions, please open an issue or send me a mail at r-pkgs@ludvigolsen.dk

Installation

Install the CRAN version with:

install.packages("xpectr")

Install the development version with:

# install.packages("devtools")  
devtools::install_github("ludvigolsen/xpectr")

Main functions

Generator functions

These functions are used to generate expectations (gxs).

Function Description
gxs_selection() Generates testthat::expect_* statements from a selection (string of code)
gxs_function() Generates testthat::expect_* statements for combinations of supplied argument values

Functions for use in tests

Function Description
strip() Strips strings of non-alphanumeric characters
strip_msg() Strips side-effect messages of non-alphanumeric characters and rethrows them
suppress_mw() Suppresses warnings and messages
capture_side_effects() Captures errors, warnings, and messages from an expression
smpl() Samples a vector, factor or data frame with internal random seed
simplified_formals() Formats formals as easily testable character vector
element_lengths(), element_types(), element_classes() Gets the length/type/class of each element
num_total_elements() Unlists recursively and finds the total number of elements
set_test_seed() Set random seed for unit tests compatible with R < 3.6.0

Helper functions

Function Description
prepare_insertion() Collapses a vector of expectation strings and adds indentation
capture_parse_eval_side_effects() Wraps string in capture_side_effects() before parsing and evaluating it
stop_if(), warn_if(), message_if() If TRUE, generate error/warning/message with the supplied message

Addins

Addin Description Suggested Key Command
Insert Expectations
insertExpectationsAddin()
Generates testthat expect_* tests from selected code (with gxs_selection()) Alt+E
Initialize test_that()
initializeTestthatAddin()
Inserts testthat::test_that() code Alt+T
Initialize gxs_function()
initializeGXSFunctionAddin()
Initializes a gxs_function() call with default values of a function Alt+F
dput() selected
dputSelectedAddin()
Applies dput() to selected code Alt+D
Wrap string with paste0()
wrapStringAddin()
Splits selected string every n characters and wraps in paste0() call Alt+P
Insert checkmate AssertCollectioncode
assertCollectionAddin()
Inserts code for initializing and reporting a checkmate AssertCollection Alt+C
Navigate To Test File
navigateTestFileAddin()
Navigates to extracted file name and line number. E.g. select or copy test_x.R:5 and it opens /tests/testthat/test_x.R at line 5. Alt+N

Using in packages

Suggestion: Add xpectr in the Suggests field in the DESCRIPTION file.

Table of Contents

Examples

library(xpectr)
library(testthat)
library(dplyr)

# Set a seed
# When R > 3.6.0, it sets sampling.kind to "Rounding" to make
# tests compatible with previous versions of R
set_test_seed(42)
# Some data
num_vec <- 1:10
long_vec <- c(LETTERS, letters)
a_factor <- factor(c("a","b","c"))

df <- data.frame(
  'a' = c(1, 2, 3),
  'b' = c('t', 'y', 'u'),
  "c" = a_factor,
  stringsAsFactors = FALSE
) %>% 
  dplyr::group_by(a)

# A function with side effects
fn <- function(raise = FALSE){
  message("Hi! I'm Kevin, your favorite message!")
  warning("G'Day Mam! I'm a warning to the world!")
  message("Kevin is ma name! Yesss!")
  warning("Hopefully the whole world will see me :o")
  if (isTRUE(raise)){
    stop("Lord Evil Error has arrived! Yeehaaa")
  }
  "the output"
}

gxs_selection

Note: gxs_selection() can be used with the Insert Expectations addin. See ?insertExpectationsAddin for instructions on how to set up a key command.

Selection is a vector

Numeric vector
# Inspect num_vec
num_vec
#>  [1]  1  2  3  4  5  6  7  8  9 10
# Generate expectations
gxs_selection("num_vec")

# Inserts the following tests:

## Testing 'num_vec'                                                        ####
## Initially generated by xpectr
xpectr::set_test_seed(42)
# Testing class
expect_equal(
  class(num_vec),
  "integer",
  fixed = TRUE)
# Testing type
expect_type(
  num_vec,
  type = "integer")
# Testing values
expect_equal(
  num_vec,
  c(1, 2, 3, 4, 5, 6, 7, 8, 9, 10),
  tolerance = 1e-4)
# Testing names
expect_equal(
  names(num_vec),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(num_vec),
  10L)
# Testing sum of element lengths
expect_equal(
  sum(xpectr::element_lengths(num_vec)),
  10L)
## Finished testing 'num_vec'                                               ####
Factor
# Inspect a_factor
a_factor
#> [1] a b c
#> Levels: a b c
# Generate expectations
gxs_selection("a_factor")

# Inserts the following tests:

## Testing 'a_factor'                                                       ####
## Initially generated by xpectr
xpectr::set_test_seed(42)
# Testing is factor
expect_true(
  is.factor(a_factor))
# Testing values
expect_equal(
  as.character(a_factor),
  c("a", "b", "c"),
  fixed = TRUE)
# Testing names
expect_equal(
  names(a_factor),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(a_factor),
  3L)
# Testing number of levels
expect_equal(
  nlevels(a_factor),
  3L)
# Testing levels
expect_equal(
  levels(a_factor),
  c("a", "b", "c"),
  fixed = TRUE)
## Finished testing 'a_factor'                                              ####
Long vector (sampling)

By default, vectors with more than 30 elements will be sampled. This adds smpl(), which temporarily sets a seed to make sure the same elements are returned every time.

# Inspect long_vec
long_vec
#>  [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
#> [20] "T" "U" "V" "W" "X" "Y" "Z" "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l"
#> [39] "m" "n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"
# Generate expectations
gxs_selection("long_vec")

# Inserts the following tests:

## Testing 'long_vec'                                                       ####
## Initially generated by xpectr
xpectr::set_test_seed(42)
# Testing class
expect_equal(
  class(long_vec),
  "character",
  fixed = TRUE)
# Testing type
expect_type(
  long_vec,
  type = "character")
# Testing values
expect_equal(
  xpectr::smpl(long_vec, n = 30),
  c("C", "E", "G", "J", "K", "N", "O", "Q", "R", "S", "T", "W", "Y", 
    "Z", "b", "c", "d", "e", "h", "i", "j", "k", "l", "o", "p", 
    "r", "v", "w", "y", "z"),
  fixed = TRUE)
# Testing names
expect_equal(
  names(xpectr::smpl(long_vec, n = 30)),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(long_vec),
  52L)
# Testing sum of element lengths
expect_equal(
  sum(xpectr::element_lengths(long_vec)),
  52L)
## Finished testing 'long_vec'                                              ####

Selection is a data frame

Data frames are tested columnwise.

# Inspect df
df
#> # A tibble: 3 x 3
#> # Groups:   a [3]
#>       a b     c    
#>   <dbl> <chr> <fct>
#> 1     1 t     a    
#> 2     2 y     b    
#> 3     3 u     c
# Generate expectations
gxs_selection("df")

# Inserts the following tests:

## Testing 'df'                                                             ####
## Initially generated by xpectr
xpectr::set_test_seed(42)
# Testing class
expect_equal(
  class(df),
  c("grouped_df", "tbl_df", "tbl", "data.frame"),
  fixed = TRUE)
# Testing column values
expect_equal(
  df[["a"]],
  c(1, 2, 3),
  tolerance = 1e-4)
expect_equal(
  df[["b"]],
  c("t", "y", "u"),
  fixed = TRUE)
expect_equal(
  df[["c"]],
  structure(1:3, .Label = c("a", "b", "c"), class = "factor"))
# Testing column names
expect_equal(
  names(df),
  c("a", "b", "c"),
  fixed = TRUE)
# Testing column classes
expect_equal(
  xpectr::element_classes(df),
  c("numeric", "character", "factor"),
  fixed = TRUE)
# Testing column types
expect_equal(
  xpectr::element_types(df),
  c("double", "character", "integer"),
  fixed = TRUE)
# Testing dimensions
expect_equal(
  dim(df),
  c(3L, 3L))
# Testing group keys
expect_equal(
  colnames(dplyr::group_keys(df)),
  "a",
  fixed = TRUE)
## Finished testing 'df'                                                    ####

Selection is a function call with side effects

When the selected code generates an error, warning or message, we can test those as well. An error is tested with expect_error(), while messages and warnings are tested as character vectors, to make sure we catch additional warnings/messages.

When running testthat unit tests on different systems, they sometimes vary in the use of punctuation and newlines (\n). The strip() and strip_msg() functions are wrapped around the side effects to remove non-alphanumeric symbols from the tested strings. This helps the expect_* functions to ignore those differences. In cases where such differences are important to catch, you can set strip = FALSE in gxs_selection().

We assign the output of the function to an output_12345 variable, so we don’t have to run it more than once. The number is randomly generated and is not guaranteed to be unique. suppress_mw() suppresses the messages and warnings.

# Inspect fn
fn
#> function(raise = FALSE){
#>   message("Hi! I'm Kevin, your favorite message!")
#>   warning("G'Day Mam! I'm a warning to the world!")
#>   message("Kevin is ma name! Yesss!")
#>   warning("Hopefully the whole world will see me :o")
#>   if (isTRUE(raise)){
#>     stop("Lord Evil Error has arrived! Yeehaaa")
#>   }
#>   "the output"
#> }
# Generate expectations
gxs_selection("fn()")

# Inserts the following tests:

## Testing 'fn()'                                                           ####
## Initially generated by xpectr
xpectr::set_test_seed(42)
# Testing side effects
# Assigning side effects
side_effects_19148 <- xpectr::capture_side_effects(fn(), reset_seed = TRUE)
expect_equal(
  xpectr::strip(side_effects_19148[['warnings']]),
  xpectr::strip(c("G'Day Mam! I'm a warning to the world!", "Hopefully the whole world will see me :o")),
  fixed = TRUE)
expect_equal(
  xpectr::strip(side_effects_19148[['messages']]),
  xpectr::strip(c("Hi! I'm Kevin, your favorite message!\n", "Kevin is ma name! Yesss!\n")),
  fixed = TRUE)
# Assigning output
output_19148 <- xpectr::suppress_mw(fn())
# Testing class
expect_equal(
  class(output_19148),
  "character",
  fixed = TRUE)
# Testing type
expect_type(
  output_19148,
  type = "character")
# Testing values
expect_equal(
  output_19148,
  "the output",
  fixed = TRUE)
# Testing names
expect_equal(
  names(output_19148),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(output_19148),
  1L)
# Testing sum of element lengths
expect_equal(
  sum(xpectr::element_lengths(output_19148)),
  1L)
## Finished testing 'fn()'                                                  ####

# In case of errors, the warnings and messages aren't tested

gxs_selection("fn(raise = TRUE)")

# Inserts the following tests:

## Testing 'fn(raise = TRUE)'                                               ####
## Initially generated by xpectr
xpectr::set_test_seed(42)
# Testing side effects
expect_error(
  xpectr::strip_msg(fn(raise = TRUE)),
  xpectr::strip("Lord Evil Error has arrived! Yeehaaa"),
  fixed = TRUE)
## Finished testing 'fn(raise = TRUE)'                                      ####

gxs_function

When testing the inputs to a function, gxs_function() allows us to quickly specify values to check and generates tests for each of them.

The first value supplied for an argument is considered the valid baseline value. For each argument, we create tests for each of the supplied values, where the other arguments have their baseline value.

By default, each argument is tested with the NULL object as well, why we only need to specify it when the baseline value should be NULL.

It is important that we manually read through the generated tests to make sure that our function is behaving as intended, and to check if any important tests are missing.

# Define a function with arguments
fn <- function(x, y, z = 10) {
  if (x > 3) stop("'x' > 3")
  if (y < 0) warning("'y'<0")
  if (z == 10) message("'z' was 10!")
  x + y + z
}

# Create tests for the function
# Note: We currently need to specify the list of arguments
# in the function call
gxs_function(fn = fn,
             args_values = list(
               "x" = list(2, 4, NA),
               "y" = list(0,-1),
               "z" = list(5, 10)
             ))

# Inserts the following tests:

## Testing 'fn'                                                             ####
## Initially generated by xpectr
# Testing different combinations of argument values

# Testing fn(x = 2, y = 0, z = 5)
xpectr::set_test_seed(42)
# Assigning output
output_19148 <- fn(x = 2, y = 0, z = 5)
# Testing class
expect_equal(
  class(output_19148),
  "numeric",
  fixed = TRUE)
# Testing type
expect_type(
  output_19148,
  type = "double")
# Testing values
expect_equal(
  output_19148,
  7,
  tolerance = 1e-4)
# Testing names
expect_equal(
  names(output_19148),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(output_19148),
  1L)
# Testing sum of element lengths
expect_equal(
  sum(xpectr::element_lengths(output_19148)),
  1L)

# Testing fn(x = 4, y = 0, z = 5)
# Changed from baseline: x = 4
xpectr::set_test_seed(42)
# Testing side effects
expect_error(
  xpectr::strip_msg(fn(x = 4, y = 0, z = 5)),
  xpectr::strip("'x' > 3"),
  fixed = TRUE)

# Testing fn(x = NA, y = 0, z = 5)
# Changed from baseline: x = NA
xpectr::set_test_seed(42)
# Testing side effects
expect_error(
  xpectr::strip_msg(fn(x = NA, y = 0, z = 5)),
  xpectr::strip("missing value where TRUE/FALSE needed"),
  fixed = TRUE)

# Testing fn(x = NULL, y = 0, z = 5)
# Changed from baseline: x = NULL
xpectr::set_test_seed(42)
# Testing side effects
expect_error(
  xpectr::strip_msg(fn(x = NULL, y = 0, z = 5)),
  xpectr::strip("argument is of length zero"),
  fixed = TRUE)

# Testing fn(x = 2, y = -1, z = 5)
# Changed from baseline: y = -1
xpectr::set_test_seed(42)
# Testing side effects
# Assigning side effects
side_effects_16417 <- xpectr::capture_side_effects(fn(x = 2, y = -1, z = 5), reset_seed = TRUE)
expect_equal(
  xpectr::strip(side_effects_16417[['warnings']]),
  xpectr::strip("'y'<0"),
  fixed = TRUE)
expect_equal(
  xpectr::strip(side_effects_16417[['messages']]),
  xpectr::strip(character(0)),
  fixed = TRUE)
# Assigning output
output_16417 <- xpectr::suppress_mw(fn(x = 2, y = -1, z = 5))
# Testing class
expect_equal(
  class(output_16417),
  "numeric",
  fixed = TRUE)
# Testing type
expect_type(
  output_16417,
  type = "double")
# Testing values
expect_equal(
  output_16417,
  6,
  tolerance = 1e-4)
# Testing names
expect_equal(
  names(output_16417),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(output_16417),
  1L)
# Testing sum of element lengths
expect_equal(
  sum(xpectr::element_lengths(output_16417)),
  1L)

# Testing fn(x = 2, y = NULL, z = 5)
# Changed from baseline: y = NULL
xpectr::set_test_seed(42)
# Testing side effects
expect_error(
  xpectr::strip_msg(fn(x = 2, y = NULL, z = 5)),
  xpectr::strip("argument is of length zero"),
  fixed = TRUE)

# Testing fn(x = 2, y = 0, z = 10)
# Changed from baseline: z = 10
xpectr::set_test_seed(42)
# Testing side effects
# Assigning side effects
side_effects_17365 <- xpectr::capture_side_effects(fn(x = 2, y = 0, z = 10), reset_seed = TRUE)
expect_equal(
  xpectr::strip(side_effects_17365[['warnings']]),
  xpectr::strip(character(0)),
  fixed = TRUE)
expect_equal(
  xpectr::strip(side_effects_17365[['messages']]),
  xpectr::strip("'z' was 10!\n"),
  fixed = TRUE)
# Assigning output
output_17365 <- xpectr::suppress_mw(fn(x = 2, y = 0, z = 10))
# Testing class
expect_equal(
  class(output_17365),
  "numeric",
  fixed = TRUE)
# Testing type
expect_type(
  output_17365,
  type = "double")
# Testing values
expect_equal(
  output_17365,
  12,
  tolerance = 1e-4)
# Testing names
expect_equal(
  names(output_17365),
  NULL,
  fixed = TRUE)
# Testing length
expect_equal(
  length(output_17365),
  1L)
# Testing sum of element lengths
expect_equal(
  sum(xpectr::element_lengths(output_17365)),
  1L)

# Testing fn(x = 2, y = 0, z = NULL)
# Changed from baseline: z = NULL
xpectr::set_test_seed(42)
# Testing side effects
expect_error(
  xpectr::strip_msg(fn(x = 2, y = 0, z = NULL)),
  xpectr::strip("argument is of length zero"),
  fixed = TRUE)

## Finished testing 'fn'                                                    ####

RStudio Addins

Below, we present the set of RStudio addins. The intention is for you to set up key commands for the ones you’d like access to. Once you get used to using them, they will speed up your testing process.

How to set up a key command in RStudio

Here’s a small guide for setting up key comands in RStudio. We use the Insert Expectations addin as an example:

After installing the package, go to:

Tools >> Addins >> Browse Addins >> Keyboard Shortcuts.

Find "Insert Expectations" and press its field under Shortcut.

Press desired key command, e.g. Alt+E.

Press Apply.

Press Execute.

initializeGXSFunctionAddin

The initializeGXSFunctionAddin initializes the gxs_function() call with the argument names and default values of a selected function. We can then add the argument values and additional combinations we wish to test. Note, that we don’t need to use the default values as our baseline values.

The Tip comment tells us to comment out the gxs_function() call after running it, instead of removing it. When you change your code, it’s often much quicker to regenerate the tests than to update them manually. You can then use a diff tool to check that only the intended changes were made.

The # in the end helps the code be inserted right after the call to gxs_function().

Suggested keycommand: Alt+F

initializeGXSFunctionAddin("fn")

# Inserts the following:

# Generate expectations for 'fn'
# Tip: comment out the gxs_function() call
# so it is easy to regenerate the tests
xpectr::set_test_seed(42)
xpectr::gxs_function(
  fn = fn,
  args_values = list(
    "x" = list(),
    "y" = list(),
    "z" = list(10)
  ),
  identation = 2
)

#

wrapStringAddin

The wrapStringAddin splits long strings and wraps them with paste0().

Suggested keycommand: Alt+P

wrapStringAddin("This is a fairly long sentence that we would very very much like to make shorter in our test file!")

# Inserts the following:

paste0("This is a fairly long sentence that we would very very much ",
       "like to make shorter in our test file!")

initializeTestthatAddin

Suggested keycommand: Alt+T

initializeTestthatAddin()

# Inserts the following:

test_that("testing ...()", {
  xpectr::set_test_seed(42)

  # ...

})

assertCollectionAddin

Suggested keycommand: Alt+C

assertCollectionAddin()

# Inserts the following:

# Check arguments ####
assert_collection <- checkmate::makeAssertCollection()
# checkmate::assert_ , add = assert_collection)
checkmate::reportAssertions(assert_collection)
# End of argument checks ####

dputSelectedAddin

Suggested keycommand: Alt+D

v <- c(1, 2, 3)

dputSelectedAddin("v")  # "v" is the selected code

# Inserts the following:

c(1, 2, 3)

navigateTestFileAddin

Suggested keycommand: Alt+N

A common work process in package development is to run Ctrl/Cmd+Shift+L, which runs all testthat tests in /tests/testthat/ in the Build pane.

When a test fails, a message like the following is printed: test_x.R:15: failure: x works.

If we then copy the test_x.R:15: part to our clipboard and run navigateTestFileAddin(), it will open the test_x.R file and place the cursor at line 15.

A service like Travis CI indicate the failed test with (@test_x.R#15). The addin therefore also works with test_x.R#15. If you have additional formats you would like to request, simply open an issue.

You can’t perform that action at this time.