diff --git a/tests/unit/style/custom_properties.rs b/tests/unit/style/custom_properties.rs
new file mode 100644
index 00000000000..135583e9d62
--- /dev/null
+++ b/tests/unit/style/custom_properties.rs
@@ -0,0 +1,49 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use cssparser::{Parser, ParserInput};
+use servo_arc::Arc;
+use style::custom_properties::{self, Name, SpecifiedValue, CustomPropertiesMap};
+use style::properties::DeclaredValue;
+use test::{self, Bencher};
+
+fn cascade(
+    name_and_value: &[(&str, &str)],
+    inherited: Option<&Arc<CustomPropertiesMap>>,
+) -> Option<Arc<CustomPropertiesMap>> {
+    let values = name_and_value.iter().map(|&(name, value)| {
+        let mut input = ParserInput::new(value);
+        let mut parser = Parser::new(&mut input);
+        (Name::from(name), SpecifiedValue::parse(&mut parser).unwrap())
+    }).collect::<Vec<_>>();
+
+    let mut custom_properties = None;
+    let mut seen = Default::default();
+    for &(ref name, ref val) in &values {
+        custom_properties::cascade(
+            &mut custom_properties,
+            inherited,
+            &mut seen,
+            name,
+            DeclaredValue::Value(val)
+        )
+    }
+
+    custom_properties::finish_cascade(custom_properties, inherited)
+}
+
+#[bench]
+fn cascade_custom_simple(b: &mut Bencher) {
+    b.iter(|| {
+        let parent = cascade(&[
+            ("foo", "10px"),
+            ("bar", "100px"),
+        ], None);
+
+        test::black_box(cascade(&[
+            ("baz", "calc(40em + 4px)"),
+            ("bazz", "calc(30em + 4px)"),
+        ], parent.as_ref()))
+    })
+}
diff --git a/tests/unit/style/lib.rs b/tests/unit/style/lib.rs
index f1774fe1a09..c1eab17d1b6 100644
--- a/tests/unit/style/lib.rs
+++ b/tests/unit/style/lib.rs
@@ -24,6 +24,7 @@ extern crate test;
 
 mod animated_properties;
 mod attr;
+mod custom_properties;
 mod keyframes;
 mod logical_geometry;
 mod media_queries;