diff --git a/src/ui/public/courier/data_source/__tests__/search_source.js b/src/ui/public/courier/data_source/__tests__/search_source.js
index 4230437d5b452..3db1e4ca78c31 100644
--- a/src/ui/public/courier/data_source/__tests__/search_source.js
+++ b/src/ui/public/courier/data_source/__tests__/search_source.js
@@ -6,6 +6,12 @@ import { requestQueue } from '../../_request_queue';
 import { SearchSourceProvider } from '../search_source';
 import StubIndexPatternProv from 'test_utils/stub_index_pattern';
 
+function timeout() {
+  return new Promise(resolve => {
+    setTimeout(resolve);
+  });
+}
+
 describe('SearchSource', function () {
   require('test_utils/no_digest_promises').activateForSuite();
 
@@ -154,6 +160,48 @@ describe('SearchSource', function () {
     });
   });
 
+  describe('#onRequestStart()', () => {
+    it('should be called when starting a request', async () => {
+      const source = new SearchSource();
+      const fn = sinon.spy();
+      source.onRequestStart(fn);
+      const request = {};
+      source.requestIsStarting(request);
+      await timeout();
+      expect(fn.calledWith(source, request)).to.be(true);
+    });
+
+    it('should not be called on parent searchSource', async () => {
+      const parent = new SearchSource();
+      const source = new SearchSource().inherits(parent);
+
+      const fn = sinon.spy();
+      source.onRequestStart(fn);
+      const parentFn = sinon.spy();
+      parent.onRequestStart(parentFn);
+      const request = {};
+      source.requestIsStarting(request);
+      await timeout();
+      expect(fn.calledWith(source, request)).to.be(true);
+      expect(parentFn.notCalled).to.be(true);
+    });
+
+    it('should be called on parent searchSource if callParentStartHandlers is true', async () => {
+      const parent = new SearchSource();
+      const source = new SearchSource().inherits(parent, { callParentStartHandlers: true });
+
+      const fn = sinon.spy();
+      source.onRequestStart(fn);
+      const parentFn = sinon.spy();
+      parent.onRequestStart(parentFn);
+      const request = {};
+      source.requestIsStarting(request);
+      await timeout();
+      expect(fn.calledWith(source, request)).to.be(true);
+      expect(parentFn.calledWith(source, request)).to.be(true);
+    });
+  });
+
   describe('#_mergeProp', function () {
     describe('filter', function () {
       let source;