diff --git a/Project.toml b/Project.toml
index 0a58776..64e45be 100644
--- a/Project.toml
+++ b/Project.toml
@@ -23,6 +23,7 @@ Dates = "1.6"
 DefaultApplication = "1"
 DocStringExtensions = "0.8, 0.9"
 EzXML = "1"
+FileCmp = "1"
 LibGit2 = "1.6"
 OrderedCollections = "1"
 Pkg = "1.6"
@@ -32,6 +33,7 @@ julia = "1.6"
 
 [extras]
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+FileCmp = "343a5541-a696-4ae7-8102-bc61c09e1896"
 
 [targets]
-test = ["Test"]
+test = ["Test","FileCmp"]
diff --git a/test/dummy.css b/test/dummy.css
new file mode 100644
index 0000000..a8cb6c2
--- /dev/null
+++ b/test/dummy.css
@@ -0,0 +1,4 @@
+body {
+    color: white;
+    background-color: black;
+}
diff --git a/test/runtests.jl b/test/runtests.jl
index deec42b..d75f1ae 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -1,4 +1,6 @@
 using LocalCoverage, Test
+using FileCmp
+
 import Pkg
 
 Pkg.activate("./DummyPackage/")
@@ -15,7 +17,8 @@ function test_coverage(pkg;
                        run_test = true, 
                        test_args = [""], 
                        folder_list = ["src"], 
-                       file_list = [])
+                       file_list = [],
+                       css = nothing)
     @info "Testing coverage for $pkg" test_args folder_list file_list
     clean_coverage(pkg)
     @test isdir(LocalCoverage.pkgdir(pkg))
@@ -47,8 +50,10 @@ function test_coverage(pkg;
 
     if !isnothing(Sys.which("genhtml"))
         mktempdir() do dir
-            html_coverage(pkg, dir = dir)
+            html_coverage(pkg, dir = dir, css = css)
             @test isfile(joinpath(dir, "index.html"))
+            isnothing(css) ||
+                @test filecmp(joinpath(dir, "gcov.css"), css)
         end
     end
 
@@ -83,6 +88,11 @@ end
                     folder_list = [joinpath(dirname(@__FILE__), "DummyPackage", "src", "corge")],
                     file_list = [joinpath(dirname(@__FILE__), "DummyPackage", "src", "qux.jl")])
     end
+
+    @testset "custom CSS" begin
+        @test_throws TypeError test_coverage("DummyPackage", css=1)
+        test_coverage("DummyPackage", css=joinpath(dirname(@__FILE__), "dummy.css"))
+    end
 end
 
 @test LocalCoverage.find_gaps([nothing, 0, 0, 0, 2, 3, 0, nothing, 0, 3, 0, 6, 2]) ==