diff --git a/NEWS.md b/NEWS.md
index 57e440f2..17a01502 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -34,6 +34,8 @@ strategy. (#353)
 
 - Increased minimum R version required to 4.0 to match {admiral}. (#382)
 
+- `addin_format_testthat` addin has been moved to `{pharmaverse4devs}` package. (#419)
+
 
 # admiraldev 1.0.0
 
diff --git a/R/addin_format_testthat.R b/R/addin_format_testthat.R
deleted file mode 100644
index df6c5b0a..00000000
--- a/R/addin_format_testthat.R
+++ /dev/null
@@ -1,107 +0,0 @@
-# Returns the call for updating a given test_that test file
-# by adding a function name, a test number, and a section.
-# Call the function either by using RStudio Addin "format_test_that_file" or
-# programmatically in a for loop on the test files and running
-# rstudioapi::navigateToFile and format_test_that_file
-prepare_test_that_file <- function(path) {
-  assert_character_scalar(path)
-
-  # check that file exists
-  if (!file.exists(path)) {
-    stop("Invalid file path, the file does not exist.")
-  }
-
-  # check that testthat is used and testing file is opened
-  uses_test_file <- grepl("tests/testthat/test-", path, fixed = TRUE)
-  if (!uses_test_file) {
-    stop("This Addin works only on unit test files that follow a testthat structure.")
-  }
-
-  # parse the name of the testing function
-  testing_file <- sub("^test-", "", sub(".R$", "", basename(path)))
-
-  # get file content
-  file_content <- readLines(path)
-
-  # get locations of tests - match 'test_that("' strings
-  test_that_loc <- grep('^test_that\\("', file_content)
-
-  if (length(test_that_loc) == 0) {
-    return(invisible(NULL))
-  }
-
-  ####
-  ## HANDLE test_that DESCRIPTIONS
-  ####
-
-  # get and parse test descriptions
-  test_that_lines <- file_content[test_that_loc]
-  test_that_desc_parsed <- stringr::str_extract(
-    string = test_that_lines,
-    pattern = paste0(
-      '(?<=test_that\\(")', # positive look-ahead - search matching expression after test_that("
-      ".*", # matching expression - match everything
-      '(?=")' # positive look-behind - search matching expression before "
-    )
-  )
-  test_that_desc_cleaned <- stringr::str_remove(
-    string = test_that_desc_parsed,
-    pattern = paste0("([\\w\\.]+,? )?[Tt]est \\d{1,} ?: ")
-  )
-
-  # determine name of function which is tested
-  # the function name can be specified by # function_name ---- comments
-  function_name <- str_match(file_content, "# ([\\w\\.]+) ----")[, 2]
-  if (is.na(function_name[1])) {
-    function_name[1] <- testing_file
-  }
-  function_name <- tidyr::fill(data.frame(name = function_name), name)$name
-  function_name <- function_name[test_that_loc]
-
-  # formulate new test descriptions (update only those that don't include test_title)
-  new_desc <- paste0(
-    "Test ", seq_along(test_that_loc), ": ",
-    test_that_desc_cleaned
-  )
-
-  # insert new test descriptions into test_that lines
-  test_that_lines_updated <- stringr::str_replace(
-    string = test_that_lines,
-    pattern = '(?<=test_that\\(").*"',
-    replacement = paste0(function_name, " ", new_desc, '"')
-  )
-
-  # modify the file content
-  file_content[test_that_loc] <- test_that_lines_updated
-
-  ####
-  ## HANDLE HEADERS
-  ####
-
-  # formulate headers according to RStudio editor functionality
-  headers <- paste0("## ", new_desc, " ----")
-
-  # get locations of headers created by this function
-  header_loc_lgl <- grepl(paste0("^##?( ----)?( \\w+)?,? [tT]est \\d{1,} ?: "), file_content)
-
-  # remove those headers
-  file_content <- file_content[!header_loc_lgl]
-
-  # add new headers just before test_that calls
-  header_loc <- grep('^test_that\\("', file_content) + seq_along(headers) - 1
-  file_content_new <- vector(mode = "character", length = length(file_content) + length(headers))
-  file_content_new[header_loc] <- headers
-  file_content_new[-header_loc] <- file_content
-
-  list(file_content = file_content_new)
-}
-
-# Function for the RStudio Addin, see inst/rstudio/addins.dcf.
-# Wrapper of prepare_test_that_file.
-format_test_that_file <- function() {
-  file_info <- rstudioapi::getActiveDocumentContext()
-  rstudioapi::documentSave(id = file_info$id)
-  result <- prepare_test_that_file(path = file_info$path)
-  rstudioapi::setDocumentContents(paste0(result$file_content, collapse = "\n"), id = file_info$id)
-  rstudioapi::documentSave(id = file_info$id)
-}
diff --git a/inst/rstudio/addins.dcf b/inst/rstudio/addins.dcf
deleted file mode 100644
index 41efae4d..00000000
--- a/inst/rstudio/addins.dcf
+++ /dev/null
@@ -1,4 +0,0 @@
-Name: Format test_that test file
-Description: Updates current test_that test file by adding a function name, a test number, and a section
-Binding: format_test_that_file
-Interactive: false
diff --git a/tests/testthat/test-addin_format_testthat.R b/tests/testthat/test-addin_format_testthat.R
deleted file mode 100644
index f9e10498..00000000
--- a/tests/testthat/test-addin_format_testthat.R
+++ /dev/null
@@ -1,49 +0,0 @@
-## Test 1: works as expected ----
-test_that("addin_format_testthat Test 1: works as expected", {
-  # test: file exists
-  expect_error(
-    prepare_test_that_file("file_does_not_exist"),
-    "Invalid file path, the file does not exist."
-  )
-
-  # test: correct file is used
-  tf <- tempfile()
-  writeLines("Hello", tf)
-  expect_error(
-    prepare_test_that_file(tf),
-    "This Addin works only on unit test files that follow a testthat structure"
-  )
-
-  # test: test_that not found
-  dir.create(file.path(tempdir(), "tests", "testthat"), recursive = TRUE)
-  tf <- tempfile(pattern = "tests/testthat/test-")
-  writeLines("Hello", tf)
-  expect_null(prepare_test_that_file(tf))
-
-  # test: headers and descriptions works as expected on dummy file
-  tf <- tempfile(pattern = "tests/testthat/test-")
-  writeLines(
-    c(
-      "# some stuff in comment",
-      'test_that("my description", {',
-      "  expect_true(TRUE)",
-      "}"
-    ),
-    tf
-  )
-  expected <- list(
-    file_content = c(
-      "# some stuff in comment",
-      paste0(
-        "## Test 1: my description ----"
-      ),
-      paste0(
-        'test_that("', sub("test-", "", basename(tf)), " ",
-        'Test 1: my description", {'
-      ),
-      "  expect_true(TRUE)",
-      "}"
-    )
-  )
-  expect_identical(prepare_test_that_file(tf), expected)
-})
diff --git a/vignettes/admiraldev.Rmd b/vignettes/admiraldev.Rmd
index fbbb88d4..06971ddf 100644
--- a/vignettes/admiraldev.Rmd
+++ b/vignettes/admiraldev.Rmd
@@ -24,7 +24,7 @@ Tools are loosely defined as follows:
 
 * Utility Functions used in `{admiral}` and `{admiral}` extension functions for doing custom checks and providing custom messages, warnings and errors.  These custom messages, warnings and errors are succinct, but helpful messaging around what a function expects as inputs. The inputs to admiral functions are many, but generally fit into three categories: datasets, variables and arguments. Most of the functions start with `assert_`, `is_` or `get_`.
 
-* Addins and utility functions that help with documentation, testing and checking on health of the code base in all admiral packages.
+* Utility functions that help with documentation, testing and checking on health of the code base in all admiral packages.
 
 * Vignettes on working on `{admiral}` functions, developing unit testing, releases process, vignette writing and other documentation needs.  These vignettes are intended for use across all admiral packages.
 
diff --git a/vignettes/unit_test_format_tests.png b/vignettes/unit_test_format_tests.png
old mode 100755
new mode 100644
index 8d2c4336..e1b4f179
Binary files a/vignettes/unit_test_format_tests.png and b/vignettes/unit_test_format_tests.png differ
diff --git a/vignettes/unit_test_guidance.Rmd b/vignettes/unit_test_guidance.Rmd
index 59a09f46..7770319a 100644
--- a/vignettes/unit_test_guidance.Rmd
+++ b/vignettes/unit_test_guidance.Rmd
@@ -211,9 +211,21 @@ knitr::include_graphics("./unit_test_toc.png")
 ```
 
 
-## Addin `admiraldev::format_test_that_file()`
+## Addin `pharmaverse4devs::format_test_that_file()`
 
-To ease the burden on developers for writing and adding tests we have developed an Addin for formatting test_that test files according to admiral programming standards. The Addin will add and update comments as well as number or re-numbers the tests. Just use the Addin button and select the "Format
+To ease the burden on developers for writing and adding tests we have developed an Addin for formatting test_that test files according to admiral programming standards. The Addin will add and update comments as well as number or re-numbers the tests. To access the Addin, be sure to install the {pharmaverse4devs} from Github. 
+
+To install the latest development version of the package directly from
+GitHub use the following code:
+```r
+    if (!requireNamespace("remotes", quietly = TRUE)) {
+      install.packages("remotes")
+    }
+
+    remotes::install_github("pharmaverse/pharmaverse4devs")
+```
+
+Then use the Addin button and select the "Format
 test_that test file" as seen in the image.  Be sure to have the test-file open and selected when calling the Addin.
 
 ```{r echo=FALSE, out.width='120%'}
@@ -237,12 +249,12 @@ prefix and the ".R" suffix.
 When writing new unit tests, just provide a description in the `test_that()`
 call and if necessary the function name in a `# <function name> ----` comment:
 ```
-# arg_name ----
-test_that("arg_name works", {
-  expect_equal(arg_name(sym("a")), "a")
-  expect_equal(arg_name(call("enquo", sym("a"))), "a")
-  expect_error(arg_name("a"), "Could not extract argument name from")
-})
+# derive_vars_merged ----
+test_that( "works if it merges all variables", {
+  actual <- derive_vars_merged(advs,
+    dataset_add = adsl,
+    by_vars = exprs(STUDYID, USUBJID)
+  )
 
 # convert_dtm_to_dtc ----
 test_that("works if dtm is in correct format", {
@@ -263,13 +275,13 @@ test_that("Error is thrown if dtm is not in correct format", {
 
 Call the addin and get:
 ```
-# arg_name ----
-## Test 1: arg_name works ----
-test_that("arg_name Test 1: arg_name works", {
-  expect_equal(arg_name(sym("a")), "a")
-  expect_equal(arg_name(call("enquo", sym("a"))), "a")
-  expect_error(arg_name("a"), "Could not extract argument name from")
-})
+# derive_vars_merged ----
+## Test 1: derive_vars_merged ----
+test_that( "derive_vars_merged Test 1: it merges all variables", {
+  actual <- derive_vars_merged(advs,
+    dataset_add = adsl,
+    by_vars = exprs(STUDYID, USUBJID)
+  )
 
 # convert_dtm_to_dtc ----
 ## Test 2: works if dtm is in correct format ----