diff --git a/tests/testthat/test-backticks.R b/tests/testthat/test-backticks.R
index 955c882ec..261d21c5b 100644
--- a/tests/testthat/test-backticks.R
+++ b/tests/testthat/test-backticks.R
@@ -1,122 +1,110 @@
-iris$`a m` <- iris$Species
-iris$`Sepal Width` <- iris$Sepal.Width
-dat <<- iris
-m <- lm(`Sepal Width` ~ Petal.Length + `a m` * log(Sepal.Length), data = dat)
-m2 <- lm(`Sepal Width` ~ Petal.Length + `a m`, data = dat)
-
-test_that("text_remove_backticks", {
-  d <- data.frame(Parameter = names(coef(m2)), Estimate = unname(coef(m2)), stringsAsFactors = FALSE)
-  expect_equal(
-    text_remove_backticks(d)$Parameter,
-    c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica")
-  )
-
-  d <- data.frame(
-    Parameter = names(coef(m2)),
-    Term = names(coef(m2)),
-    Estimate = unname(coef(m2)),
-    stringsAsFactors = FALSE
-  )
-  x <- text_remove_backticks(d, c("Parameter", "Term"))
-  expect_equal(x$Parameter, c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica"))
-  expect_equal(x$Term, c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica"))
-
-  d <- list(Parameter = names(coef(m2)), Estimate = unname(coef(m2)))
-  expect_warning(text_remove_backticks(d, verbose = TRUE))
-  expect_equal(
-    text_remove_backticks(d),
-    list(
-      Parameter = c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica"),
-      Estimate = c(2.99186937324135, 0.298310962215218, -1.49267407227818, -1.67409183546024)
-    ),
-    tolerance = 1e-3
-  )
-})
-
-test_that("backticks", {
-  expect_equal(
-    find_parameters(m),
-    list(conditional = c(
-      "(Intercept)", "Petal.Length", "a mversicolor",
-      "a mvirginica", "log(Sepal.Length)", "a mversicolor:log(Sepal.Length)",
-      "a mvirginica:log(Sepal.Length)"
-    ))
-  )
-
-  expect_equal(
-    get_parameters(m)$Parameter,
-    c(
-      "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica", "log(Sepal.Length)",
-      "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+skip_if_not_installed("withr")
+
+withr::with_environment(
+  new.env(),
+  test_that("text_remove_backticks", {
+    iris$`a m` <- iris$Species
+    iris$`Sepal Width` <- iris$Sepal.Width
+    dat <- iris
+    m <- lm(`Sepal Width` ~ Petal.Length + `a m` * log(Sepal.Length), data = dat)
+    m2 <- lm(`Sepal Width` ~ Petal.Length + `a m`, data = dat)
+
+    d <- data.frame(Parameter = names(coef(m2)), Estimate = unname(coef(m2)), stringsAsFactors = FALSE)
+    expect_identical(
+      text_remove_backticks(d)$Parameter,
+      c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica")
     )
-  )
 
-  expect_equal(
-    get_statistic(m)$Parameter,
-    c(
-      "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica", "log(Sepal.Length)",
-      "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+    d <- data.frame(
+      Parameter = names(coef(m2)),
+      Term = names(coef(m2)),
+      Estimate = unname(coef(m2)),
+      stringsAsFactors = FALSE
     )
-  )
-
-  expect_equal(
-    clean_parameters(m)$Parameter,
-    c(
-      "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica", "log(Sepal.Length)",
-      "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+    x <- text_remove_backticks(d, c("Parameter", "Term"))
+    expect_identical(x$Parameter, c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica"))
+    expect_identical(x$Term, c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica"))
+
+    d <- list(Parameter = names(coef(m2)), Estimate = unname(coef(m2)))
+    expect_warning(text_remove_backticks(d, verbose = TRUE))
+    expect_equal(
+      text_remove_backticks(d),
+      list(
+        Parameter = c("(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica"),
+        Estimate = c(2.99186937324135, 0.298310962215218, -1.49267407227818, -1.67409183546024)
+      ),
+      tolerance = 1e-3
     )
-  )
-
-  expect_equal(
-    find_predictors(m),
-    list(conditional = c("Petal.Length", "a m", "Sepal.Length"))
-  )
-
-  expect_equal(
-    colnames(get_predictors(m)),
-    c("Petal.Length", "a m", "Sepal.Length")
-  )
-
-  expect_equal(
-    find_variables(m),
-    list(
-      response = "Sepal Width",
-      conditional = c("Petal.Length", "a m", "Sepal.Length")
+    expect_identical(
+      find_parameters(m),
+      list(conditional = c(
+        "(Intercept)", "Petal.Length", "a mversicolor",
+        "a mvirginica", "log(Sepal.Length)", "a mversicolor:log(Sepal.Length)",
+        "a mvirginica:log(Sepal.Length)"
+      ))
     )
-  )
-
-  expect_equal(
-    find_terms(m),
-    list(
-      response = "Sepal Width",
-      conditional = c("Petal.Length", "a m", "log(Sepal.Length)")
+    expect_identical(
+      get_parameters(m)$Parameter,
+      c(
+        "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica", "log(Sepal.Length)",
+        "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+      )
     )
-  )
-
-  expect_equal(
-    rownames(get_varcov(m)),
-    c(
-      "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica",
-      "log(Sepal.Length)", "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+    expect_identical(
+      get_statistic(m)$Parameter,
+      c(
+        "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica", "log(Sepal.Length)",
+        "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+      )
     )
-  )
-
-  expect_equal(
-    clean_names(m),
-    c("Sepal Width", "Petal.Length", "a m", "Sepal.Length")
-  )
-
-  expect_equal(find_response(m), "Sepal Width")
-
-  expect_equal(get_response(m), iris[["Sepal Width"]])
-})
+    expect_identical(
+      clean_parameters(m)$Parameter,
+      c(
+        "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica", "log(Sepal.Length)",
+        "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+      )
+    )
+    expect_identical(
+      find_predictors(m),
+      list(conditional = c("Petal.Length", "a m", "Sepal.Length"))
+    )
+    expect_identical(
+      find_variables(m),
+      list(
+        response = "Sepal Width",
+        conditional = c("Petal.Length", "a m", "Sepal.Length")
+      )
+    )
+    expect_identical(
+      find_terms(m),
+      list(
+        response = "Sepal Width",
+        conditional = c("Petal.Length", "a m", "log(Sepal.Length)")
+      )
+    )
+    expect_identical(
+      rownames(get_varcov(m)),
+      c(
+        "(Intercept)", "Petal.Length", "a mversicolor", "a mvirginica",
+        "log(Sepal.Length)", "a mversicolor:log(Sepal.Length)", "a mvirginica:log(Sepal.Length)"
+      )
+    )
+    expect_identical(
+      clean_names(m),
+      c("Sepal Width", "Petal.Length", "a m", "Sepal.Length")
+    )
+    expect_identical(find_response(m), "Sepal Width")
+    expect_identical(get_response(m), iris[["Sepal Width"]])
+    expect_named(get_predictors(m), c("Petal.Length", "a m", "Sepal.Length"))
+  })
+)
 
 
 test_that("text_remove_backticks, character", {
   x <- "`test`"
-  expect_equal(text_remove_backticks(x), "test")
+  expect_identical(text_remove_backticks(x), "test")
   x <- "test"
-  expect_equal(text_remove_backticks(x), "test")
+  expect_identical(text_remove_backticks(x), "test")
   x <- NULL
   expect_null(text_remove_backticks(x))
 })
@@ -125,13 +113,13 @@ test_that("text_remove_backticks, character", {
 test_that("text_remove_backticks, matrix", {
   x <- matrix(1:9, nrow = 3)
   out <- text_remove_backticks(x)
-  expect_equal(dimnames(x), dimnames(out))
+  expect_identical(dimnames(x), dimnames(out))
 
   colnames(x) <- rownames(x) <- 1:3
   out <- text_remove_backticks(x)
-  expect_equal(dimnames(x), dimnames(out))
+  expect_identical(dimnames(x), dimnames(out))
 
   colnames(x) <- rownames(x) <- paste0("`", 1:3, "`")
   out <- text_remove_backticks(x)
-  expect_equal(list(as.character(1:3), as.character(1:3)), dimnames(out))
+  expect_identical(list(as.character(1:3), as.character(1:3)), dimnames(out))
 })
diff --git a/tests/testthat/test-coxme.R b/tests/testthat/test-coxme.R
index 5d71b6a7a..e211a94e0 100644
--- a/tests/testthat/test-coxme.R
+++ b/tests/testthat/test-coxme.R
@@ -3,198 +3,186 @@ skip_if_not_installed("lme4")
 skip_if_not_installed("nlme")
 skip_if_not_installed("bdsmatrix")
 skip_if_not_installed("coxme")
-
-lung <- survival::lung
-Surv <- survival::Surv
-
-set.seed(1234)
-lung$inst2 <- sample(1:10, size = nrow(lung), replace = TRUE)
-lung <- subset(lung, subset = ph.ecog %in% 0:2)
-lung$ph.ecog <- factor(lung$ph.ecog, labels = c("good", "ok", "limited"))
-
-d <<- lung
-
-m1 <- coxme::coxme(Surv(time, status) ~ ph.ecog + age + (1 | inst), d)
-m2 <- coxme::coxme(Surv(time, status) ~ ph.ecog + age + (1 | inst) + (1 | inst2), d)
-
-test_that("model_info", {
-  expect_true(model_info(m1)$is_logit)
-  expect_false(model_info(m1)$is_linear)
-})
-
-test_that("find_predictors", {
-  expect_identical(find_predictors(m1), list(conditional = c("ph.ecog", "age")))
-  expect_identical(
-    find_predictors(m1, effects = "random"),
-    list(random = "inst")
-  )
-  expect_identical(find_predictors(m2), list(conditional = c("ph.ecog", "age")))
-  expect_identical(find_predictors(m2, effects = "random"), list(random = c("inst", "inst2")))
-})
-
-test_that("find_response", {
-  expect_identical(find_response(m1), "Surv(time, status)")
-  expect_identical(find_response(m1, combine = FALSE), c("time", "status"))
-})
-
-test_that("link_inverse", {
-  expect_equal(link_inverse(m1)(0.2), plogis(0.2), tolerance = 1e-5)
-  expect_equal(link_inverse(m2)(0.2), plogis(0.2), tolerance = 1e-5)
-})
-
-test_that("get_data", {
-  expect_equal(nrow(get_data(m1)), 225)
-  expect_equal(
-    colnames(get_data(m1)),
-    c(
-      "time",
-      "status",
-      "ph.ecog",
-      "age",
-      "inst"
-    )
-  )
-  expect_equal(
-    colnames(get_data(m2)),
-    c(
-      "time",
-      "status",
-      "ph.ecog",
-      "age",
-      "inst",
-      "inst2"
-    )
-  )
-})
-
-test_that("find_formula", {
-  expect_length(find_formula(m1), 2)
-  expect_equal(
-    find_formula(m1),
-    list(
-      conditional = as.formula("Surv(time, status) ~ ph.ecog + age"),
-      random = as.formula("~1 | inst")
-    ),
-    ignore_attr = TRUE
-  )
-
-  expect_length(find_formula(m2), 2)
-  expect_equal(
-    find_formula(m2),
-    list(
-      conditional = as.formula("Surv(time, status) ~ ph.ecog + age"),
-      random = list(as.formula("~1 | inst"), as.formula("~1 | inst2"))
-    ),
-    ignore_attr = TRUE
-  )
-})
-
-test_that("find_terms", {
-  expect_equal(
-    find_terms(m1),
-    list(
-      response = "Surv(time, status)",
-      conditional = c("ph.ecog", "age"),
-      random = "inst"
-    )
-  )
-  expect_equal(
-    find_terms(m1, flatten = TRUE),
-    c("Surv(time, status)", "ph.ecog", "age", "inst")
-  )
-  expect_equal(
-    find_terms(m2),
-    list(
-      response = "Surv(time, status)",
-      conditional = c("ph.ecog", "age"),
-      random = c("inst", "inst2")
-    )
-  )
-  expect_equal(
-    find_terms(m2, flatten = TRUE),
-    c("Surv(time, status)", "ph.ecog", "age", "inst", "inst2")
-  )
-})
-
-test_that("find_variables", {
-  expect_equal(
-    find_variables(m1),
-    list(
-      response = c("time", "status"),
-      conditional = c("ph.ecog", "age"),
-      random = "inst"
-    )
-  )
-  expect_equal(
-    find_variables(m1, flatten = TRUE),
-    c("time", "status", "ph.ecog", "age", "inst")
-  )
-  expect_equal(
-    find_variables(m2),
-    list(
-      response = c("time", "status"),
-      conditional = c("ph.ecog", "age"),
-      random = c("inst", "inst2")
-    )
-  )
-  expect_equal(
-    find_variables(m2, flatten = TRUE),
-    c("time", "status", "ph.ecog", "age", "inst", "inst2")
-  )
-})
-
-test_that("n_obs", {
-  expect_equal(n_obs(m1), 225)
-  expect_equal(n_obs(m2), 225)
-})
-
-test_that("get_response", {
-  expect_equal(colnames(get_response(m1)), c("time", "status"))
-  expect_equal(nrow(get_response(m1)), 225)
-  expect_equal(colnames(get_response(m1)), c("time", "status"))
-  expect_equal(nrow(get_response(m2)), 225)
-})
-
-test_that("linkfun", {
-  expect_false(is.null(link_function(m1)))
-  expect_false(is.null(link_function(m2)))
-})
-
-test_that("is_multivariate", {
-  expect_false(is_multivariate(m1))
-})
-
-test_that("find_parameters", {
-  expect_equal(
-    find_parameters(m1),
-    list(
-      conditional = c("ph.ecogok", "ph.ecoglimited", "age"),
-      random = "inst"
-    )
-  )
-  expect_equal(
-    find_parameters(m2),
-    list(
-      conditional = c("ph.ecogok", "ph.ecoglimited", "age"),
-      random = c("inst", "inst2")
-    )
-  )
-  expect_equal(nrow(get_parameters(m1)), 3)
-  expect_equal(
-    get_parameters(m1)$Parameter,
-    c("ph.ecogok", "ph.ecoglimited", "age")
-  )
-
-  expect_equal(nrow(get_parameters(m2)), 3)
-  expect_equal(
-    get_parameters(m2)$Parameter,
-    c("ph.ecogok", "ph.ecoglimited", "age")
-  )
-
-  expect_length(get_parameters(m2, effects = "random"), 2)
-})
-
-test_that("find_statistic", {
-  expect_identical(find_statistic(m1), "z-statistic")
-  expect_identical(find_statistic(m2), "z-statistic")
-})
+skip_if_not_installed("withr")
+
+withr::with_environment(
+  new.env(),
+  {
+    lung <- survival::lung
+    Surv <- survival::Surv
+
+    set.seed(1234)
+    lung$inst2 <- sample(1:10, size = nrow(lung), replace = TRUE)
+    lung <- subset(lung, subset = ph.ecog %in% 0:2)
+    lung$ph.ecog <- factor(lung$ph.ecog, labels = c("good", "ok", "limited"))
+
+    d <<- lung
+
+    m1 <- coxme::coxme(Surv(time, status) ~ ph.ecog + age + (1 | inst), d)
+    m2 <- coxme::coxme(Surv(time, status) ~ ph.ecog + age + (1 | inst) + (1 | inst2), d)
+
+    test_that("model_info", {
+      expect_true(model_info(m1)$is_logit)
+      expect_false(model_info(m1)$is_linear)
+    })
+
+    test_that("find_predictors", {
+      expect_identical(find_predictors(m1), list(conditional = c("ph.ecog", "age")))
+      expect_identical(
+        find_predictors(m1, effects = "random"),
+        list(random = "inst")
+      )
+      expect_identical(find_predictors(m2), list(conditional = c("ph.ecog", "age")))
+      expect_identical(find_predictors(m2, effects = "random"), list(random = c("inst", "inst2")))
+    })
+
+    test_that("find_response", {
+      expect_identical(find_response(m1), "Surv(time, status)")
+      expect_identical(find_response(m1, combine = FALSE), c("time", "status"))
+    })
+
+    test_that("link_inverse", {
+      expect_equal(link_inverse(m1)(0.2), plogis(0.2), tolerance = 1e-5)
+      expect_equal(link_inverse(m2)(0.2), plogis(0.2), tolerance = 1e-5)
+    })
+
+    test_that("get_data", {
+      expect_identical(nrow(get_data(m1)), 225L)
+      expect_named(get_data(m1), c("time", "status", "ph.ecog", "age", "inst"))
+      expect_named(get_data(m2), c("time", "status", "ph.ecog", "age", "inst", "inst2"))
+    })
+
+    test_that("find_formula", {
+      expect_length(find_formula(m1), 2)
+      expect_equal(
+        find_formula(m1),
+        list(
+          conditional = as.formula("Surv(time, status) ~ ph.ecog + age"),
+          random = as.formula("~1 | inst")
+        ),
+        ignore_attr = TRUE
+      )
+
+      expect_length(find_formula(m2), 2)
+      expect_equal(
+        find_formula(m2),
+        list(
+          conditional = as.formula("Surv(time, status) ~ ph.ecog + age"),
+          random = list(as.formula("~1 | inst"), as.formula("~1 | inst2"))
+        ),
+        ignore_attr = TRUE
+      )
+    })
+
+    test_that("find_terms", {
+      expect_identical(
+        find_terms(m1),
+        list(
+          response = "Surv(time, status)",
+          conditional = c("ph.ecog", "age"),
+          random = "inst"
+        )
+      )
+      expect_identical(
+        find_terms(m1, flatten = TRUE),
+        c("Surv(time, status)", "ph.ecog", "age", "inst")
+      )
+      expect_identical(
+        find_terms(m2),
+        list(
+          response = "Surv(time, status)",
+          conditional = c("ph.ecog", "age"),
+          random = c("inst", "inst2")
+        )
+      )
+      expect_identical(
+        find_terms(m2, flatten = TRUE),
+        c("Surv(time, status)", "ph.ecog", "age", "inst", "inst2")
+      )
+    })
+
+    test_that("find_variables", {
+      expect_identical(
+        find_variables(m1),
+        list(
+          response = c("time", "status"),
+          conditional = c("ph.ecog", "age"),
+          random = "inst"
+        )
+      )
+      expect_identical(
+        find_variables(m1, flatten = TRUE),
+        c("time", "status", "ph.ecog", "age", "inst")
+      )
+      expect_identical(
+        find_variables(m2),
+        list(
+          response = c("time", "status"),
+          conditional = c("ph.ecog", "age"),
+          random = c("inst", "inst2")
+        )
+      )
+      expect_identical(
+        find_variables(m2, flatten = TRUE),
+        c("time", "status", "ph.ecog", "age", "inst", "inst2")
+      )
+    })
+
+    test_that("n_obs", {
+      expect_identical(n_obs(m1), 225)
+      expect_identical(n_obs(m2), 225)
+    })
+
+    test_that("get_response", {
+      expect_named(get_response(m1), c("time", "status"))
+      expect_identical(nrow(get_response(m1)), 225L)
+      expect_named(get_response(m1), c("time", "status"))
+      expect_identical(nrow(get_response(m2)), 225L)
+    })
+
+    test_that("linkfun", {
+      expect_false(is.null(link_function(m1)))
+      expect_false(is.null(link_function(m2)))
+    })
+
+    test_that("is_multivariate", {
+      expect_false(is_multivariate(m1))
+    })
+
+    test_that("find_parameters", {
+      expect_identical(
+        find_parameters(m1),
+        list(
+          conditional = c("ph.ecogok", "ph.ecoglimited", "age"),
+          random = "inst"
+        )
+      )
+      expect_identical(
+        find_parameters(m2),
+        list(
+          conditional = c("ph.ecogok", "ph.ecoglimited", "age"),
+          random = c("inst", "inst2")
+        )
+      )
+      expect_identical(nrow(get_parameters(m1)), 3L)
+      expect_identical(
+        get_parameters(m1)$Parameter,
+        c("ph.ecogok", "ph.ecoglimited", "age")
+      )
+
+      expect_identical(nrow(get_parameters(m2)), 3L)
+      expect_identical(
+        get_parameters(m2)$Parameter,
+        c("ph.ecogok", "ph.ecoglimited", "age")
+      )
+
+      expect_length(get_parameters(m2, effects = "random"), 2)
+    })
+
+    test_that("find_statistic", {
+      expect_identical(find_statistic(m1), "z-statistic")
+      expect_identical(find_statistic(m2), "z-statistic")
+    })
+
+  }
+)
diff --git a/tests/testthat/test-coxph.R b/tests/testthat/test-coxph.R
index 2539e195b..e2af4da30 100644
--- a/tests/testthat/test-coxph.R
+++ b/tests/testthat/test-coxph.R
@@ -1,6 +1,7 @@
 skip_if_not_installed("survival")
 skip_if_not_installed("insight")
 skip_if_not_installed("JM")
+skip_if_not_installed("withr")
 
 lung <- subset(survival::lung, subset = ph.ecog %in% 0:2)
 lung$sex <- factor(lung$sex, labels = c("male", "female"))
@@ -36,41 +37,44 @@ test_that("get_data", {
   ## NOTE check back every now and then and see if tests still work
   skip("works interactively")
   expect_s3_class(get_data(m1), "data.frame")
-  expect_equal(dim(get_data(m1)), c(166, 10))
+  expect_identical(dim(get_data(m1)), c(166L, 10L))
 })
 
-test_that("get_data: regression test for previous bug", {
-  ## NOTE check back every now and then and see if tests still work
-  skip("works interactively")
-  dat_regression_test <- data.frame(
-    time = c(4, 3, 1, 1, 2, 2, 3),
-    status = c(1, 1, 1, 0, 1, 1, 0),
-    x = c(0, 2, 1, 1, 1, 0, 0),
-    sex = c(0, 0, 0, 0, 1, 1, 1)
-  )
-  mod <- survival::coxph(Surv(time, status) ~ x + strata(sex),
-    data = dat_regression_test,
-    ties = "breslow"
-  )
-  expect_equal(get_data(mod), dat_regression_test, ignore_attr = TRUE)
-})
 
-
-test_that("get_data: regression test for data stored as list", {
-  ## NOTE check back every now and then and see if tests still work
-  skip("works interactively")
-  dat_regression_test <- list(
-    time = c(4, 3, 1, 1, 2, 2, 3),
-    status = c(1, 1, 1, 0, 1, 1, 0),
-    x = c(0, 2, 1, 1, 1, 0, 0),
-    sex = c(0, 0, 0, 0, 1, 1, 1)
-  )
-  mod <- coxph(Surv(time, status) ~ x + strata(sex),
-    data = dat_regression_test,
-    ties = "breslow"
-  )
-  expect_equal(get_data(mod), as.data.frame(dat_regression_test), ignore_attr = TRUE)
-})
+withr::with_environment(
+  new.env(),
+  test_that("get_data: regression test for previous bug", {
+    dat_regression_test <- data.frame(
+      time = c(4, 3, 1, 1, 2, 2, 3),
+      status = c(1, 1, 1, 0, 1, 1, 0),
+      x = c(0, 2, 1, 1, 1, 0, 0),
+      sex = c(0, 0, 0, 0, 1, 1, 1)
+    )
+    mod <- survival::coxph(Surv(time, status) ~ x + strata(sex),
+      data = dat_regression_test,
+      ties = "breslow"
+    )
+    expect_equal(get_data(mod), dat_regression_test, ignore_attr = TRUE)
+  })
+)
+
+
+withr::with_environment(
+  new.env(),
+  test_that("get_data: regression test for data stored as list", {
+    dat_regression_test <- list(
+      time = c(4, 3, 1, 1, 2, 2, 3),
+      status = c(1, 1, 1, 0, 1, 1, 0),
+      x = c(0, 2, 1, 1, 1, 0, 0),
+      sex = c(0, 0, 0, 0, 1, 1, 1)
+    )
+    mod <- survival::coxph(Surv(time, status) ~ x + strata(sex),
+      data = dat_regression_test,
+      ties = "breslow"
+    )
+    expect_equal(get_data(mod), as.data.frame(dat_regression_test), ignore_attr = TRUE)
+  })
+)
 
 
 test_that("find_formula", {
@@ -85,18 +89,18 @@ test_that("find_formula", {
 })
 
 test_that("find_variables", {
-  expect_equal(find_variables(m1), list(
+  expect_identical(find_variables(m1), list(
     response = c("time", "status"),
     conditional = c("sex", "age", "ph.ecog")
   ))
-  expect_equal(
+  expect_identical(
     find_variables(m1, flatten = TRUE),
     c("time", "status", "sex", "age", "ph.ecog")
   )
 })
 
 test_that("n_obs", {
-  expect_equal(n_obs(m1), 226)
+  expect_identical(n_obs(m1), 226L)
 })
 
 test_that("linkfun", {
@@ -108,21 +112,21 @@ test_that("is_multivariate", {
 })
 
 test_that("find_parameters", {
-  expect_equal(
+  expect_identical(
     find_parameters(m1),
     list(
       conditional = c("sexfemale", "age", "ph.ecogok", "ph.ecoglimited")
     )
   )
-  expect_equal(nrow(get_parameters(m1)), 4)
-  expect_equal(
+  expect_identical(nrow(get_parameters(m1)), 4L)
+  expect_identical(
     get_parameters(m1)$Parameter,
     c("sexfemale", "age", "ph.ecogok", "ph.ecoglimited")
   )
 })
 
 test_that("find_terms", {
-  expect_equal(
+  expect_identical(
     find_terms(m1),
     list(
       response = "Surv(time, status)",
@@ -139,9 +143,9 @@ test_that("JM", {
   data("aids", package = "JM")
   m <- survival::coxph(Surv(start, stop, event) ~ CD4, data = aids)
   d <- get_data(m)
-  expect_equal(dim(d), c(1405, 4))
-  expect_equal(colnames(d), c("start", "stop", "event", "CD4"))
-  expect_equal(find_variables(m), list(response = c("start", "stop", "event"), conditional = "CD4"))
+  expect_identical(dim(d), c(1405L, 4L))
+  expect_named(d, c("start", "stop", "event", "CD4"))
+  expect_identical(find_variables(m), list(response = c("start", "stop", "event"), conditional = "CD4"))
 })
 
 test_that("get_statistic", {
diff --git a/tests/testthat/test-fixest.R b/tests/testthat/test-fixest.R
index 576f60db9..8048063eb 100644
--- a/tests/testthat/test-fixest.R
+++ b/tests/testthat/test-fixest.R
@@ -2,6 +2,7 @@ skip_on_os("mac")
 skip_if(getRversion() < "3.6.0")
 skip_if_not_installed("fixest")
 skip_if_not_installed("carData")
+skip_if_not_installed("withr")
 
 # avoid warnings
 fixest::setFixest_nthreads(1)
@@ -298,32 +299,33 @@ test_that("get_predicted", {
   expect_warning(get_predicted(m1, predict = NULL, type = "link"), NA)
 })
 
-test_that("get_data works when model data has name of  reserved words", {
-  ## NOTE check back every now and then and see if tests still work
-  skip("works interactively")
-  rep <- data.frame(Y = runif(100) > 0.5, X = rnorm(100))
-  m <- fixest::feglm(Y ~ X, data = rep, family = binomial)
-  out <- get_data(m)
-  expect_s3_class(out, "data.frame")
-  expect_equal(
-    head(out),
-    structure(
-      list(
-        Y = c(TRUE, TRUE, TRUE, TRUE, FALSE, FALSE),
+
+withr::with_environment(
+  new.env(),
+  test_that("get_data works when model data has name of reserved words", {
+    set.seed(1234)
+    rep <- data.frame(Y = runif(100) > 0.5, X = rnorm(100))
+    m <- fixest::feglm(Y ~ X, data = rep, family = binomial)
+    out <- get_data(m)
+    expect_s3_class(out, "data.frame")
+    expect_equal(
+      head(out),
+      data.frame(
+        Y = c(FALSE, TRUE, TRUE, TRUE, TRUE, TRUE),
         X = c(
-          -1.37601434046896, -0.0340090992175856, 0.418083058388383,
-          -0.51688491498936, -1.30634551903768, -0.858343109785566
+          -1.80603125680195, -0.582075924689333, -1.10888962442678,
+          -1.01496200949201, -0.162309523556819, 0.563055818994517
         )
       ),
-      is_subset = FALSE, row.names = c(NA, 6L), class = "data.frame"
-    ),
-    ignore_attr = TRUE,
-    tolerance = 1e-3
-  )
-})
+      ignore_attr = TRUE,
+      tolerance = 1e-3
+    )
+  })
+)
 
 
 test_that("find_variables with interaction", {
+  data(mtcars)
   mod <- suppressMessages(fixest::feols(mpg ~ 0 | carb | vs:cyl ~ am:cyl, data = mtcars))
   expect_equal(
     find_variables(mod),
@@ -341,15 +343,14 @@ test_that("find_variables with interaction", {
 
 
 test_that("find_predictors with i(f1, i.f2) interaction", {
+  data(airquality)
   aq <- airquality
   aq$week <- aq$Day %/% 7 + 1
 
   mod <- fixest::feols(Ozone ~ i(Month, i.week), aq, notes = FALSE)
   expect_equal(
     find_predictors(mod),
-    list(
-      conditional = c("Month", "week")
-    ),
+    list(conditional = c("Month", "week")),
     ignore_attr = TRUE
   )
 })