diff --git a/test/sortedDomain.test.js b/test/sortedDomain.test.js
new file mode 100644
index 000000000..130f6745e
--- /dev/null
+++ b/test/sortedDomain.test.js
@@ -0,0 +1,67 @@
+import { sortedDomain } from "../src/util/sortedDomain";
+
+test("sortedDomain works correctly in normal case", () => {
+  const stateCount = new Map([
+    ["Italy", 8],
+    ["Lombardy", 9],
+    ["USA", 1],
+    ["Iran", 18],
+    ["Comunitat Valenciana", 1],
+    ["Hubei", 35],
+    ["China", 2],
+    ["Grand Princess", 2],
+    ["Hong Kong", 1],
+    ["South Korea", 1],
+    ["Europe", 1],
+    ["UK", 1]
+  ]);
+  const domain = stateCount.keys();
+  const sorted = sortedDomain(domain, "", stateCount);
+  expect(sorted).toMatchObject([
+    "Hubei",
+    "Iran",
+    "Lombardy",
+    "Italy",
+    "China",
+    "Grand Princess",
+    "Comunitat Valenciana",
+    "Europe",
+    "Hong Kong",
+    "South Korea",
+    "UK",
+    "USA"
+  ]);
+});
+
+test("sortedDomain works correctly in special case", () => {
+  const stateCount = new Map([
+    ["Italy", 8],
+    ["Lombardy", 9],
+    ["USA", 1],
+    ["Iran", 18],
+    ["Comunitat Valenciana", 1],
+    ["Hubei", 35],
+    ["China", 2],
+    ["Grand Princess", 2],
+    ["Hong Kong", 1],
+    ["South Korea", 1],
+    ["Europe", 1],
+    ["UK", 1]
+  ]);
+  const domain = stateCount.keys();
+  const sorted = sortedDomain(domain, "clade_membership", stateCount);
+  expect(sorted).toMatchObject([
+    "China",
+    "Comunitat Valenciana",
+    "Europe",
+    "Grand Princess",
+    "Hong Kong",
+    "Hubei",
+    "Iran",
+    "Italy",
+    "Lombardy",
+    "South Korea",
+    "UK",
+    "USA"
+  ]);
+});