diff --git a/src/dev/build/lib/__mocks__/get_build_number.ts b/src/dev/build/lib/__mocks__/get_build_number.ts
new file mode 100644
index 0000000000000..60cfd3d82557a
--- /dev/null
+++ b/src/dev/build/lib/__mocks__/get_build_number.ts
@@ -0,0 +1,22 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+export function getBuildNumber() {
+  return 12345;
+}
diff --git a/src/dev/build/lib/get_build_number.ts b/src/dev/build/lib/get_build_number.ts
new file mode 100644
index 0000000000000..c512042592002
--- /dev/null
+++ b/src/dev/build/lib/get_build_number.ts
@@ -0,0 +1,34 @@
+/*
+ * Licensed to Elasticsearch B.V. under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch B.V. licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+import os from 'os';
+import execa from 'execa';
+
+export async function getBuildNumber() {
+  if (/^win/.test(os.platform())) {
+    // Windows does not have the wc process and `find /C /V ""` does not consistently work
+    const log = await execa('git', ['log', '--format="%h"']);
+    return log.stdout.split('\n').length;
+  }
+
+  const wc = await execa.command('git log --format="%h" | wc -l', {
+    shell: true,
+  });
+  return parseFloat(wc.stdout.trim());
+}
diff --git a/src/dev/build/lib/version_info.test.ts b/src/dev/build/lib/version_info.test.ts
index 1b0c71bf9220e..ec8c363ddaccf 100644
--- a/src/dev/build/lib/version_info.test.ts
+++ b/src/dev/build/lib/version_info.test.ts
@@ -20,6 +20,8 @@
 import pkg from '../../../../package.json';
 import { getVersionInfo } from './version_info';
 
+jest.mock('./get_build_number');
+
 describe('isRelease = true', () => {
   it('returns unchanged package.version, build sha, and build number', async () => {
     const versionInfo = await getVersionInfo({
diff --git a/src/dev/build/lib/version_info.ts b/src/dev/build/lib/version_info.ts
index 958112c524bac..fb3530b4c4edf 100644
--- a/src/dev/build/lib/version_info.ts
+++ b/src/dev/build/lib/version_info.ts
@@ -17,22 +17,8 @@
  * under the License.
  */
 
-import os from 'os';
-
 import execa from 'execa';
-
-async function getBuildNumber() {
-  if (/^win/.test(os.platform())) {
-    // Windows does not have the wc process and `find /C /V ""` does not consistently work
-    const log = await execa('git', ['log', '--format="%h"']);
-    return log.stdout.split('\n').length;
-  }
-
-  const wc = await execa.command('git log --format="%h" | wc -l', {
-    shell: true,
-  });
-  return parseFloat(wc.stdout.trim());
-}
+import { getBuildNumber } from './get_build_number';
 
 interface Options {
   isRelease: boolean;
diff --git a/src/dev/build/tasks/nodejs/download_node_builds_task.test.ts b/src/dev/build/tasks/nodejs/download_node_builds_task.test.ts
index 6f08c8aa69750..413bf95cde877 100644
--- a/src/dev/build/tasks/nodejs/download_node_builds_task.test.ts
+++ b/src/dev/build/tasks/nodejs/download_node_builds_task.test.ts
@@ -26,13 +26,10 @@ import {
 import { Config, Platform } from '../../lib';
 import { DownloadNodeBuilds } from './download_node_builds_task';
 
-// import * as NodeShasumsNS from '../node_shasums';
-// import * as NodeDownloadInfoNS from '../node_download_info';
-// import * as DownloadNS from '../../../lib/download';
-// import { DownloadNodeBuilds } from '../download_node_builds_task';
 jest.mock('./node_shasums');
 jest.mock('./node_download_info');
 jest.mock('../../lib/download');
+jest.mock('../../lib/get_build_number');
 
 expect.addSnapshotSerializer(createAnyInstanceSerializer(ToolingLog));
 
diff --git a/src/dev/build/tasks/nodejs/extract_node_builds_task.test.ts b/src/dev/build/tasks/nodejs/extract_node_builds_task.test.ts
index 94c421f7c9a62..f1700ef7b578c 100644
--- a/src/dev/build/tasks/nodejs/extract_node_builds_task.test.ts
+++ b/src/dev/build/tasks/nodejs/extract_node_builds_task.test.ts
@@ -27,6 +27,7 @@ import { Config } from '../../lib';
 import { ExtractNodeBuilds } from './extract_node_builds_task';
 
 jest.mock('../../lib/fs');
+jest.mock('../../lib/get_build_number');
 
 const Fs = jest.requireMock('../../lib/fs');
 
diff --git a/src/dev/build/tasks/nodejs/verify_existing_node_builds_task.test.ts b/src/dev/build/tasks/nodejs/verify_existing_node_builds_task.test.ts
index f24b7ffc59c14..19416963d5edd 100644
--- a/src/dev/build/tasks/nodejs/verify_existing_node_builds_task.test.ts
+++ b/src/dev/build/tasks/nodejs/verify_existing_node_builds_task.test.ts
@@ -29,6 +29,7 @@ import { VerifyExistingNodeBuilds } from './verify_existing_node_builds_task';
 jest.mock('./node_shasums');
 jest.mock('./node_download_info');
 jest.mock('../../lib/fs');
+jest.mock('../../lib/get_build_number');
 
 const { getNodeShasums } = jest.requireMock('./node_shasums');
 const { getNodeDownloadInfo } = jest.requireMock('./node_download_info');