diff --git a/.github/workflows/test-coverage.yaml b/.github/workflows/test-coverage.yaml
deleted file mode 100644
index 2c5bb50..0000000
--- a/.github/workflows/test-coverage.yaml
+++ /dev/null
@@ -1,50 +0,0 @@
-# Workflow derived from https://github.com/r-lib/actions/tree/v2/examples
-# Need help debugging build failures? Start at https://github.com/r-lib/actions#where-to-find-help
-on:
-  push:
-    branches: [main, master]
-  pull_request:
-    branches: [main, master]
-
-name: test-coverage
-
-jobs:
-  test-coverage:
-    runs-on: ubuntu-latest
-    env:
-      GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
-
-    steps:
-      - uses: actions/checkout@v3
-
-      - uses: r-lib/actions/setup-r@v2
-        with:
-          use-public-rspm: true
-
-      - uses: r-lib/actions/setup-r-dependencies@v2
-        with:
-          extra-packages: any::covr
-          needs: coverage
-
-      - name: Test coverage
-        run: |
-          covr::codecov(
-            quiet = FALSE,
-            clean = FALSE,
-            install_path = file.path(Sys.getenv("RUNNER_TEMP"), "package")
-          )
-        shell: Rscript {0}
-
-      - name: Show testthat output
-        if: always()
-        run: |
-          ## --------------------------------------------------------------------
-          find ${{ runner.temp }}/package -name 'testthat.Rout*' -exec cat '{}' \; || true
-        shell: bash
-
-      - name: Upload test results
-        if: failure()
-        uses: actions/upload-artifact@v3
-        with:
-          name: coverage-test-failures
-          path: ${{ runner.temp }}/package
diff --git a/.lintr b/.lintr
index 28b31d1..7f3d75a 100644
--- a/.lintr
+++ b/.lintr
@@ -1,4 +1,4 @@
-linters: with_defaults(line_length_linter(90))
+linters: linters_with_defaults (line_length_linter(90))
 exclude: "# Exclude Linting"
 exclude_start: "# Begin Exclude Linting"
 exclude_end: "# End Exclude Linting"
diff --git a/DESCRIPTION b/DESCRIPTION
index 90d9472..58c8c44 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,6 +1,6 @@
 Package: shinyusertracking
 Title: Add user tracking to Shiny apps
-Version: 1.0.0.000
+Version: 1.0.1.000
 Authors@R: 
     person(
       "Mark", "McPherson", , 
@@ -11,13 +11,8 @@ Description: Log session and user data to a Google sheet.
 License: MIT + file LICENSE
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)
-RoxygenNote: 7.2.2
-Suggests: 
-    covr,
-    testthat (>= 3.0.0)
+RoxygenNote: 7.3.1
 Config/testthat/edition: 3
 Imports: 
-    shiny,
     googlesheets4,
-    hms,
     lubridate
diff --git a/R/usertracking.R b/R/usertracking.R
index f7bfaa1..0ea8b6e 100644
--- a/R/usertracking.R
+++ b/R/usertracking.R
@@ -1,11 +1,10 @@
-
 #' Add user tracking
 #'
 #' Log session ID, username (only for Private apps), session start, end and
 #' duration to a Google sheet.
 #'
-#' @param google_email Email used for Google account username.
-#' @param sheet_id Google sheet ID.
+#' @param columns Which columns to record, from id, username, login, logout and
+#'  duration. By default all will be recorded.
 #' @param session Shiny session object.
 #'
 #' @return Nothing; used for side effect.
@@ -18,8 +17,7 @@
 #' ui <- fluidPage()
 #' server <- function(input, output, session) {
 #'   shinyusertracking::set_user_tracking(
-#'     "joe.bloggs@google.com",
-#'     "1234567890987654321",
+#'     c("login", "logout", "duration"),
 #'     session
 #'   )
 #' }
@@ -27,9 +25,41 @@
 #' shinyApp(ui, server)
 #' }
 #'
-set_user_tracking <- function(google_email, sheet_id, session) {
-  if (sheet_id == "") {
-    return(invisible())
+set_user_tracking <- function(columns = NULL, session) {
+  known_cols <- c(
+    "id",
+    "username",
+    "login",
+    "logout",
+    "duration"
+  )
+
+  if (is.null(columns)) {
+    columns <- known_cols
+  } else {
+    stopifnot({
+      columns %in% known_cols
+    })
+  }
+
+  eval_lines(".google-sheets-credentials")
+
+  google_email <- NULL
+  sheet_id <- NULL
+
+  try({
+    google_email <- get("GOOGLE_SHEET_USER")
+  })
+  try({
+    sheet_id <- get("GOOGLE_SHEET_ID")
+  })
+
+  if (is.null(google_email) || is.null(sheet_id)) {
+    warning(
+      "Credentials missing for shinyusertracking::set_user_tracking",
+      call. = FALSE
+    )
+    return()
   }
 
   googlesheets4::gs4_auth(
@@ -37,34 +67,67 @@ set_user_tracking <- function(google_email, sheet_id, session) {
     cache = ".secret/"
   )
 
-  shiny::isolate({
-    userdata <<- userdata <- data.frame( # Exclude Linting
-      id = session$token,
-      username = ifelse(is.null(session$user), "unknown", session$user),
-      login = Sys.time(),
-      logout = lubridate::NA_POSIXct_,
-      duration = NA_character_
-    )
-  })
+  session$userData$tracking <- data.frame(
+    id = session$token,
+    username = ifelse(is.null(session$user), "unknown", session$user),
+    login = Sys.time(),
+    logout = lubridate::NA_POSIXct_,
+    duration = NA_character_
+  )
 
   session$onSessionEnded(function() {
-    shiny::isolate({
-      userdata[userdata$id == session$token, "logout"] <- Sys.time()
-      userdata[userdata$id == session$token, "duration"] <- as.character(
-        hms::hms(
-          round(
-            lubridate::as.period(
-              userdata[userdata$id == session$token, "logout"] -
-                userdata[userdata$id == session$token, "login"],
-              "seconds"
-            )
-          )
-        )
-      )
+    session$userData$tracking$logout <- Sys.time()
 
-      googlesheets4::sheet_append(sheet_id, userdata)
-    })
+    duration <- difftime(
+      session$userData$tracking$logout,
+      session$userData$tracking$login,
+      units = "secs"
+    )
+    duration <- abs(as.numeric(duration))
+    duration <- sprintf(
+      "%02d:%02d:%02d", # hh:mm:ss
+      duration %/% 3600, # whole hours (could be > 24)
+      duration %% 3600 %/% 60, # whole minutes left
+      duration %% 60 %/% 1 + round(duration %% 60 %% 1) # rounded seconds left
+    )
+
+    session$userData$tracking$duration <- as.character(duration)
+
+    googlesheets4::sheet_append(
+      sheet_id,
+      subset(session$userData$tracking, select = columns)
+    )
   })
+}
+
+
+#' Evaluate each line of plain text file
+#'
+#' Reads a plain text file line by line, evaluating each line. Useful for
+#' creating variables dynamically, e.g. reading in parameters.
+#'
+#' @param filepath Filepath as a String.
+#' @param envir Environment to evaluate in. Default is calling environment.
+#'
+#' @return Nothing
+#'
+#' @examples
+#' \dontrun{
+#' filepath <- tempfile()
+#' writeLines(
+#'   text = "LEFT = \"right\"",
+#'   con = filepath
+#' )
+#' eval_lines(filepath)
+#' print(LEFT)
+#' unlink(filepath) # delete temporary file
+#' rm(left) # remove example variable
+#' }
+eval_lines <- function(filepath, envir = parent.frame()) {
+  con <- file(filepath, open = "r")
+  on.exit(close(con))
 
-  invisible()
+  while (length(line <- readLines(con, n = 1, warn = FALSE)) > 0) {
+    eval(parse(text = line), envir = envir)
+  }
 }
diff --git a/README.md b/README.md
index 11b4114..51ef9d7 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,6 @@
 # shinyusertracking
 
 <!-- badges: start -->
-[![Codecov test coverage](https://codecov.io/gh/MarkMc1089/shinyusertracking/branch/master/graph/badge.svg)](https://app.codecov.io/gh/MarkMc1089/shinyusertracking?branch=master)
 [![R-CMD-check](https://github.com/MarkMc1089/shinyusertracking/actions/workflows/R-CMD-check.yaml/badge.svg)](https://github.com/MarkMc1089/shinyusertracking/actions/workflows/R-CMD-check.yaml)
 <!-- badges: end -->
 
@@ -19,7 +18,7 @@ devtools::install_github("nhsbsa-data-analytics/shinyusertracking")
 
 ## Example
 
-Just add the function at the top of your `server` code. You will need to provide the ID of a Google Sheet and the username (email) of the Google account it is in.
+Just add the function at the top of your `server` code. You will need to provide the ID of a Google Sheet and the username (email) of the Google account it is in. 
 
 ``` r
 library(shiny)
@@ -28,11 +27,26 @@ ui <- fluidPage()
   
 server <- function(input, output, session) {
   shinyusertracking::set_user_tracking(
-    "joe.bloggs@google.com",
-    "1234567890987654321",
     session
   )
 }
 
 shinyApp(ui, server)
 ```
+
+Optionally, you can choose to log specific columns only.
+
+Column|Description
+:---:|:---: 
+id|The Shiny session ID
+username|The username of user, if available (`null` if app is public)
+login|Timestamp of session start
+logout|Timestamp of session end
+duration|Duration of session in `hh:mm:ss` format
+
+``` r
+shinyusertracking::set_user_tracking(
+  columns = c("login", "logout", "duration"),
+  session
+)   
+```
diff --git a/codecov.yml b/codecov.yml
deleted file mode 100644
index 04c5585..0000000
--- a/codecov.yml
+++ /dev/null
@@ -1,14 +0,0 @@
-comment: false
-
-coverage:
-  status:
-    project:
-      default:
-        target: auto
-        threshold: 1%
-        informational: true
-    patch:
-      default:
-        target: auto
-        threshold: 1%
-        informational: true
diff --git a/man/eval_lines.Rd b/man/eval_lines.Rd
new file mode 100644
index 0000000..337e68e
--- /dev/null
+++ b/man/eval_lines.Rd
@@ -0,0 +1,33 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/usertracking.R
+\name{eval_lines}
+\alias{eval_lines}
+\title{Evaluate each line of plain text file}
+\usage{
+eval_lines(filepath, envir = parent.frame())
+}
+\arguments{
+\item{filepath}{Filepath as a String.}
+
+\item{envir}{Environment to evaluate in. Default is calling environment.}
+}
+\value{
+Nothing
+}
+\description{
+Reads a plain text file line by line, evaluating each line. Useful for
+creating variables dynamically, e.g. reading in parameters.
+}
+\examples{
+\dontrun{
+filepath <- tempfile()
+writeLines(
+  text = "LEFT = \"right\"",
+  con = filepath
+)
+eval_lines(filepath)
+print(LEFT)
+unlink(filepath) # delete temporary file
+rm(left) # remove example variable
+}
+}
diff --git a/man/set_user_tracking.Rd b/man/set_user_tracking.Rd
index b152b87..54d017d 100644
--- a/man/set_user_tracking.Rd
+++ b/man/set_user_tracking.Rd
@@ -4,12 +4,11 @@
 \alias{set_user_tracking}
 \title{Add user tracking}
 \usage{
-set_user_tracking(google_email, sheet_id, session)
+set_user_tracking(columns = NULL, session)
 }
 \arguments{
-\item{google_email}{Email used for Google account username.}
-
-\item{sheet_id}{Google sheet ID.}
+\item{columns}{Which columns to record, from id, username, login, logout and
+duration. By default all will be recorded.}
 
 \item{session}{Shiny session object.}
 }
@@ -27,8 +26,7 @@ library(shiny)
 ui <- fluidPage()
 server <- function(input, output, session) {
   shinyusertracking::set_user_tracking(
-    "joe.bloggs@google.com",
-    "1234567890987654321",
+    c("login", "logout", "duration"),
     session
   )
 }
diff --git a/tests/testthat.R b/tests/testthat.R
deleted file mode 100644
index 638376b..0000000
--- a/tests/testthat.R
+++ /dev/null
@@ -1,12 +0,0 @@
-# This file is part of the standard setup for testthat.
-# It is recommended that you do not modify it.
-#
-# Where should you do additional test configuration?
-# Learn more about the roles of various files in:
-# * https://r-pkgs.org/tests.html
-# * https://testthat.r-lib.org/reference/test_package.html#special-files
-
-library(testthat)
-library(shinyusertracking)
-
-test_check("shinyusertracking")
diff --git a/tests/testthat/test-usertracking.R b/tests/testthat/test-usertracking.R
deleted file mode 100644
index 8849056..0000000
--- a/tests/testthat/test-usertracking.R
+++ /dev/null
@@ -1,3 +0,0 @@
-test_that("multiplication works", {
-  expect_equal(2 * 2, 4)
-})