diff --git a/libs/utils/src/namespaces/fonts.ts b/libs/utils/src/namespaces/fonts.ts
index 14fcc09d..4af07c5b 100644
--- a/libs/utils/src/namespaces/fonts.ts
+++ b/libs/utils/src/namespaces/fonts.ts
@@ -6,7 +6,18 @@ export type Font = {
   files: Record<string, string>;
 };
 
+/**
+ * Known system fonts we consider available locally without fetching from Google Fonts.
+ * Extend this list when adding more system-safe families to the app.
+ */
 export const localFonts = ["Arial", "Cambria", "Garamond", "Times New Roman"];
+
+/**
+ * Checks whether a font family is a local/system font.
+ *
+ * Input: font family name (case-insensitive)
+ * Output: true if present in localFonts, otherwise false
+ */
 export const isLocalFont = (family: string): boolean =>
   localFonts.some((f) => f.toLowerCase() === family.toLowerCase());
 
diff --git a/libs/utils/src/namespaces/tests/fonts.test.ts b/libs/utils/src/namespaces/tests/fonts.test.ts
new file mode 100644
index 00000000..ec1832e7
--- /dev/null
+++ b/libs/utils/src/namespaces/tests/fonts.test.ts
@@ -0,0 +1,24 @@
+import { describe, it, expect } from "vitest";
+import { isLocalFont, localFonts } from "../fonts";
+
+describe("isLocalFont", () => {
+  it("returns true for known local fonts (case-insensitive)", () => {
+    expect(isLocalFont("Arial")).toBe(true);
+    expect(isLocalFont("arial")).toBe(true);
+    expect(isLocalFont("Times New Roman")).toBe(true);
+    expect(isLocalFont("times new roman")).toBe(true);
+  });
+
+  it("returns false for non-local fonts", () => {
+    expect(isLocalFont("Roboto")).toBe(false);
+    expect(isLocalFont("Open Sans")).toBe(false);
+  });
+});
+
+describe("localFonts", () => {
+  it("includes the expected base set", () => {
+    for (const f of ["Arial", "Cambria", "Garamond", "Times New Roman"]) {
+      expect(localFonts).toContain(f);
+    }
+  });
+});