diff --git a/__mocks__/gatsby-plugin-firebase.js b/__mocks__/gatsby-plugin-firebase.js
index bc84e9fc..97d9bdf7 100644
--- a/__mocks__/gatsby-plugin-firebase.js
+++ b/__mocks__/gatsby-plugin-firebase.js
@@ -157,9 +157,12 @@ const database = () => {
   };
 };
 
-database.ServerValue = {
-  TIMESTAMP: Date.now(),
-};
+database.ServerValue = {};
+Object.defineProperty(database.ServerValue, 'TIMESTAMP', {
+  get() {
+    return new Date().getTime();
+  },
+});
 
 export default class firebase {
   static auth = auth;
diff --git a/src/pages/app/__tests__/builder.test.js b/src/pages/app/__tests__/builder.test.js
index bd548b82..30908682 100644
--- a/src/pages/app/__tests__/builder.test.js
+++ b/src/pages/app/__tests__/builder.test.js
@@ -78,7 +78,7 @@ describe('builder', () => {
 
       await ref.update({
         ...resume,
-        updatedAt: firebaseMock.database().ServerValue.TIMESTAMP,
+        updatedAt: firebaseMock.database.ServerValue.TIMESTAMP,
       });
 
       await waitFor(() =>
diff --git a/src/pages/app/__tests__/mock.test.js b/src/pages/app/__tests__/mock.test.js
new file mode 100644
index 00000000..3e7429c9
--- /dev/null
+++ b/src/pages/app/__tests__/mock.test.js
@@ -0,0 +1,42 @@
+import { cleanup, waitFor } from '@testing-library/react';
+
+import firebaseMock from 'gatsby-plugin-firebase';
+
+beforeEach(() => {
+  firebaseMock.database().__init();
+});
+
+afterEach(cleanup);
+
+describe('builder', () => {
+  let resumeId = null;
+  let resume = null;
+
+  beforeEach(async () => {
+    resumeId = firebaseMock.database().__demoResumeId;
+    resume = (
+      await firebaseMock.database().ref(`resumes/${resumeId}`).once('value')
+    ).val();
+  });
+
+  it('test 1', async () => {
+    const now = new Date().getTime();
+    const newInputValue = 'test street 123';
+    resume.profile.address.line1 = newInputValue;
+    const ref = firebaseMock.database().ref(`resumes/${resumeId}`);
+    const functionSpy = jest.spyOn(ref, 'update');
+
+    await ref.update({
+      ...resume,
+      updatedAt: firebaseMock.database.ServerValue.TIMESTAMP,
+    });
+
+    await waitFor(() => expect(functionSpy).toHaveBeenCalledTimes(1), {
+      timeout: 4000,
+    });
+    const functionCallArgument = functionSpy.mock.calls[0][0];
+    expect(functionCallArgument.id).toBe(resume.id);
+    expect(functionCallArgument.profile.address.line1).toBe(newInputValue);
+    expect(functionCallArgument.updatedAt).toBeGreaterThanOrEqual(now);
+  });
+});