diff --git a/tests/testthat/test-error_if_field_not_in_df.R b/tests/testthat/test-error_if_field_not_in_df.R
new file mode 100644
index 0000000..e950f99
--- /dev/null
+++ b/tests/testthat/test-error_if_field_not_in_df.R
@@ -0,0 +1,48 @@
+## Test error_if_field_not_in_df() ----
+
+### Data for tests ----
+
+test_error_if_field_not_in_df <- function(data, column) {
+  error_if_field_not_in_df(data, column)
+  invisible(NULL)
+}
+
+good_data <- sf::st_read(system.file(file.path("extdata", 
+                                               "marine_fish_richness.gpkg"), 
+                                     package = "rphenofish"), quiet = TRUE)
+bad_col  <- "missing_column"
+good_col <- "ECOREGION"
+
+
+### Tests for errors ----
+
+test_that("Test error_if_field_not_in_df() for error", {
+  
+  expect_error(error_if_field_not_in_df(good_data, bad_col),
+               "The column listed in 'bad_col' is absent from 'good_data'",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_field_not_in_df(good_data, bad_col),
+               "The column listed in 'column' is absent from 'data'",
+               fixed = TRUE)
+  
+  expect_error(error_if_field_not_in_df(good_data, c(good_col, good_col)),
+               "Argument 'c(good_col, good_col)' must be a `character` of length 1",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_field_not_in_df(good_data, c(good_col, good_col)),
+               "Argument 'column' must be a `character` of length 1",
+               fixed = TRUE)
+})
+
+
+### Tests for success ----
+
+test_that("Test error_if_field_not_in_df() for success", {
+  
+  expect_silent(error_if_field_not_in_df(good_data, good_col))
+  expect_silent(test_error_if_field_not_in_df(good_data, good_col))
+  
+  expect_invisible(x <- error_if_field_not_in_df(good_data, good_col))
+  expect_invisible(x <- test_error_if_field_not_in_df(good_data, good_col))
+})
diff --git a/tests/testthat/test-error_if_missing.R b/tests/testthat/test-error_if_missing.R
new file mode 100644
index 0000000..2c10dc2
--- /dev/null
+++ b/tests/testthat/test-error_if_missing.R
@@ -0,0 +1,34 @@
+## Test error_if_missing() ----
+
+### Data for tests ----
+
+test_error_if_missing <- function(data) {
+  error_if_missing(data)
+  invisible(NULL)
+}
+
+
+### Tests for errors ----
+
+test_that("Test error_if_missing() for error", {
+  
+  expect_error(error_if_missing(),
+               "Argument '' is required",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_missing(),
+               "Argument 'data' is required",
+               fixed = TRUE)
+})
+
+
+### Tests for success ----
+
+test_that("Test error_if_missing() for success", {
+  
+  expect_silent(error_if_missing(iris))
+  expect_silent(test_error_if_missing(iris))
+
+  expect_invisible(x <- error_if_missing(iris))
+  expect_invisible(x <- test_error_if_missing(iris))
+})
diff --git a/tests/testthat/test-error_if_not_character.R b/tests/testthat/test-error_if_not_character.R
new file mode 100644
index 0000000..0bba22c
--- /dev/null
+++ b/tests/testthat/test-error_if_not_character.R
@@ -0,0 +1,50 @@
+## Test error_if_not_character() ----
+
+### Data for tests ----
+
+test_error_if_not_character <- function(data) {
+  error_if_not_character(data)
+  invisible(NULL)
+}
+
+
+### Tests for errors ----
+
+test_that("Test error_if_not_character() for error", {
+  
+  expect_error(error_if_not_character(1),
+               "Argument '1' must be a `character`",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_character(iris),
+               "Argument 'iris' must be a `character`",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_character(NULL),
+               "Argument 'NULL' must be a `character`",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_character(1),
+               "Argument 'data' must be a `character`",
+               fixed = TRUE)
+
+  expect_error(test_error_if_not_character(iris),
+               "Argument 'data' must be a `character`",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_character(NULL),
+               "Argument 'data' must be a `character`",
+               fixed = TRUE)
+})
+
+
+### Tests for success ----
+
+test_that("Test error_if_not_character() for success", {
+  
+  expect_silent(error_if_not_character("this is a character"))
+  expect_silent(test_error_if_not_character("this is a character"))
+  
+  expect_invisible(x <- error_if_not_character("this is a character"))
+  expect_invisible(x <- test_error_if_not_character("this is a character"))
+})
diff --git a/tests/testthat/test-error_if_not_length_of.R b/tests/testthat/test-error_if_not_length_of.R
new file mode 100644
index 0000000..9cb65cb
--- /dev/null
+++ b/tests/testthat/test-error_if_not_length_of.R
@@ -0,0 +1,81 @@
+## Test error_if_not_length_of() ----
+
+### Data for tests ----
+
+test_error_if_not_length_of <- function(data, n) {
+  error_if_not_length_of(data, n)
+  invisible(NULL)
+}
+
+
+
+### Tests for errors ----
+
+test_that("Test error_if_not_length_of() for error", {
+  
+  expect_error(error_if_not_length_of("length_1", n = "length_1"),
+               "Argument 'n' must be a `numeric`",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_length_of("length_1", n = NULL),
+               "Argument 'n' must be a `numeric`",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_length_of("length_1", n = NA),
+               "Argument 'n' must be a `numeric`",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_length_of("length_1", n = 1:2),
+               "Argument 'n' must be a `numeric` of length 1",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_length_of("length_1", n = 2),
+               "Argument '\"length_1\"' must be of length 2",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_length_of(rep("length_1", 2), n = 1),
+               "Argument 'rep(\"length_1\", 2)' must be of length 1",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_length_of("length_1", n = "length_1"),
+               "Argument 'n' must be a `numeric`",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_length_of("length_1", n = NULL),
+               "Argument 'n' must be a `numeric`",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_length_of("length_1", n = NA),
+               "Argument 'n' must be a `numeric`",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_length_of("length_1", n = 1:2),
+               "Argument 'n' must be a `numeric` of length 1",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_length_of("length_1", n = 2),
+               "Argument 'data' must be of length 2",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_length_of(rep("length_1", 2), n = 1),
+               "Argument 'data' must be of length 1",
+               fixed = TRUE)
+})
+
+
+### Tests for success ----
+
+test_that("Test error_if_not_length_of() for success", {
+  
+  expect_silent(error_if_not_length_of("length_1", 1))
+  expect_silent(test_error_if_not_length_of("length_1", 1))
+  
+  expect_invisible(x <- error_if_not_length_of("length_1", 1))
+  expect_invisible(x <- test_error_if_not_length_of("length_1", 1))
+  
+  expect_silent(error_if_not_length_of(rep("length_1", 2), 2))
+  expect_silent(test_error_if_not_length_of(rep("length_1", 2), 2))
+  
+  expect_invisible(x <- error_if_not_length_of(rep("length_1", 2), 2))
+  expect_invisible(x <- test_error_if_not_length_of(rep("length_1", 2), 2))
+})
diff --git a/tests/testthat/test-error_if_not_sf.R b/tests/testthat/test-error_if_not_sf.R
new file mode 100644
index 0000000..194c8e6
--- /dev/null
+++ b/tests/testthat/test-error_if_not_sf.R
@@ -0,0 +1,47 @@
+## Test error_if_not_sf() ----
+
+### Data for tests ----
+
+test_error_if_not_sf <- function(data) {
+  error_if_not_sf(data)
+  invisible(NULL)
+}
+
+bad_data  <- iris
+good_data <- sf::st_read(system.file(file.path("extdata", 
+                                               "marine_fish_richness.gpkg"), 
+                                     package = "rphenofish"), quiet = TRUE)
+
+
+### Tests for errors ----
+
+test_that("Test error_if_not_sf() for error", {
+  
+  expect_error(error_if_not_sf(bad_data),
+               "Argument 'bad_data' must be an `sf` object",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_sf(bad_data),
+               "Argument 'data' must be an `sf` object",
+               fixed = TRUE)
+  
+  expect_error(error_if_not_sf(good_data[0, ]),
+               "Argument 'good_data[0, ]' must have at least one row",
+               fixed = TRUE)
+  
+  expect_error(test_error_if_not_sf(good_data[0, ]),
+               "Argument 'data' must have at least one row",
+               fixed = TRUE)
+})
+
+
+### Tests for success ----
+
+test_that("Test error_if_not_sf() for success", {
+  
+  expect_silent(error_if_not_sf(good_data))
+  expect_silent(test_error_if_not_sf(good_data))
+  
+  expect_invisible(x <- error_if_not_sf(good_data))
+  expect_invisible(x <- test_error_if_not_sf(good_data))
+})