diff --git a/packages/rpc/__tests__/custom-fetch.test.js b/packages/rpc/__tests__/custom-fetch.test.js
new file mode 100644
index 000000000..3147dd42e
--- /dev/null
+++ b/packages/rpc/__tests__/custom-fetch.test.js
@@ -0,0 +1,25 @@
+const { RPC } = require("..");
+
+describe("custom fetch", () => {
+  test("should work", async () => {
+    const customizedFetch = jest.fn((_, { body }) =>
+      Promise.resolve({
+        json: () =>
+          Promise.resolve({
+            jsonrpc: "2.0",
+            result: "0x8dd",
+            id: JSON.parse(body).id,
+          }),
+      })
+    );
+
+    const rpc = new RPC("", { fetch: customizedFetch });
+    await rpc.getTipBlockNumber();
+
+    expect(customizedFetch).toBeCalled();
+    expect(JSON.parse(customizedFetch.mock.calls[0][1].body)).toHaveProperty(
+      "method",
+      "get_tip_block_number"
+    );
+  });
+});