diff --git a/R/fips.R b/R/fips.R
index a33e38e..7f9e86f 100644
--- a/R/fips.R
+++ b/R/fips.R
@@ -86,9 +86,8 @@ fips <- function(state, county = c()) {
       result <- c(
         result,
         df$fips[which(
-          (name %in% county_i | name %in% paste(county_i, "county"))
-          &
-          (state_abbr %in% state_ | state_full %in% state_)
+          (name %in% county_i | name %in% paste(county_i, "county")) &
+            (state_abbr %in% state_ | state_full %in% state_)
         )]
       )
     }
diff --git a/R/plot-map.R b/R/plot-map.R
index 3b16e24..1e91b9b 100644
--- a/R/plot-map.R
+++ b/R/plot-map.R
@@ -123,7 +123,8 @@ plot_usmap <- function(regions = c("states", "state", "counties", "county"),
       centroid_labels <- centroid_labels[
         centroid_labels$full %in% include |
           centroid_labels$abbr %in% include |
-          centroid_labels$fips %in% include, ]
+          centroid_labels$fips %in% include,
+      ]
     }
 
     if (length(exclude) > 0) {
@@ -131,18 +132,21 @@ plot_usmap <- function(regions = c("states", "state", "counties", "county"),
         centroid_labels$full %in% exclude |
           centroid_labels$abbr %in% exclude |
           centroid_labels$fips %in% exclude |
-          substr(centroid_labels$fips, 1, 2) %in% exclude), ]
+          substr(centroid_labels$fips, 1, 2) %in% exclude
+      ), ]
     }
 
     if (regions_ == "county" || regions_ == "counties") {
       label_layer <- ggplot2::geom_text(
         data = centroid_labels,
         ggplot2::aes(x = .data$x, y = .data$y, label = sub(" County", "", .data$county)),
-        color = label_color)
+        color = label_color
+      )
     } else {
       label_layer <- ggplot2::geom_text(
         data = centroid_labels,
-        ggplot2::aes(x = .data$x, y = .data$y, label = .data$abbr), color = label_color)
+        ggplot2::aes(x = .data$x, y = .data$y, label = .data$abbr), color = label_color
+      )
     }
   } else {
     label_layer <- ggplot2::geom_blank()
diff --git a/R/transform.R b/R/transform.R
index addf21b..c34f573 100644
--- a/R/transform.R
+++ b/R/transform.R
@@ -153,9 +153,9 @@ usmap_transform.data.frame <- function(data,
 
   hawaii <- transformed[
     transformed@coords[, 1] >= hi_bbox[1, 1] &
-    transformed@coords[, 1] <= hi_bbox[1, 2] &
-    transformed@coords[, 2] >= hi_bbox[2, 1] &
-    transformed@coords[, 2] <= hi_bbox[2, 2],
+      transformed@coords[, 1] <= hi_bbox[1, 2] &
+      transformed@coords[, 2] >= hi_bbox[2, 1] &
+      transformed@coords[, 2] <= hi_bbox[2, 2],
   ]
 
   if (length(hawaii) > 0) {
diff --git a/tests/testthat/helper-requireNamespace-mock.R b/tests/testthat/helper-requireNamespace-mock.R
new file mode 100644
index 0000000..ec0d4bf
--- /dev/null
+++ b/tests/testthat/helper-requireNamespace-mock.R
@@ -0,0 +1,12 @@
+
+# Mocks `requireNamespace` to return `FALSE` for
+# provided dependency package "pkg" to test that
+# error occurs when it's not installed.
+expect_package_error <- function(pkg, code, msg) {
+  testthat::with_mocked_bindings({
+    testthat::expect_error(code, paste0("`", pkg, "` must be installed"))
+  },
+  requireNamespace = function(package, ...) package != pkg,
+  .package = "base"
+  )
+}
diff --git a/tests/testthat/test-plot.R b/tests/testthat/test-plot.R
index 68a4a6f..7946bd8 100644
--- a/tests/testthat/test-plot.R
+++ b/tests/testthat/test-plot.R
@@ -1,5 +1,9 @@
 context("Plotting US maps")
 
+test_that("dependencies are verified", {
+  expect_package_error("ggplot2", plot_usmap())
+})
+
 library(proto)
 
 example_data <- data.frame(
diff --git a/tests/testthat/test-transform.R b/tests/testthat/test-transform.R
index 7b2b6a0..a27e2f4 100644
--- a/tests/testthat/test-transform.R
+++ b/tests/testthat/test-transform.R
@@ -1,5 +1,12 @@
 context("Transforming coordinate data frames")
 
+test_that("dependencies are verified", {
+  expect_package_error("sf", usmap_transform(data.frame()))
+  expect_package_error("sp", usmap_transform(data.frame()))
+  expect_package_error("sf", usmap_crs())
+  expect_package_error("sp", usmap_crs())
+})
+
 test_that("data frame with AK and HI points is transformed", {
   data <- data.frame(
     lon = c(-74.01, -95.36, -118.24, -87.65, -134.42, -157.86),
@@ -104,3 +111,9 @@ test_that("error occurs for data with non-numeric columns", {
   expect_error(usmap_transform(invalid_data2))
   expect_error(usmap_transform(invalid_data3))
 })
+
+test_that("sp evolution status is set correctly", {
+  sp::set_evolution_status(1L)
+  usmap_transform(data.frame(lon = 0, lat = 0))
+  expect_equal(sp::get_evolution_status(), 2L)
+})
diff --git a/tests/testthat/test-usmap.R b/tests/testthat/test-usmap.R
new file mode 100644
index 0000000..5a8cb32
--- /dev/null
+++ b/tests/testthat/test-usmap.R
@@ -0,0 +1,11 @@
+context("Retrieving US map data")
+
+test_that("dependencies are verified", {
+  expect_package_error("usmapdata", us_map())
+})
+
+test_that("data frame is returned", {
+  data <- us_map()
+  expect_equal(length(data), 9)
+  expect_equal(length(data$x), 13663)
+})