diff --git a/search/test/backendsearch_test.py b/search/test/backendsearch_test.py
new file mode 100644
index 0000000..dd5ed18
--- /dev/null
+++ b/search/test/backendsearch_test.py
@@ -0,0 +1,126 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+"""Unittests for monorail.search.backendsearch."""
+from __future__ import print_function
+from __future__ import division
+from __future__ import absolute_import
+
+import unittest
+import mox
+
+import settings
+from search import backendsearch
+from search import backendsearchpipeline
+from services import service_manager
+from testing import fake
+from testing import testing_helpers
+
+
+class BackendSearchTest(unittest.TestCase):
+
+  def setUp(self):
+    self.services = service_manager.Services(
+        issue=fake.IssueService(),
+        )
+    self.mr = testing_helpers.MakeMonorailRequest(
+        path='/_backend/besearch?q=Priority:High&shard=2')
+    self.mr.query_project_names = ['proj']
+    self.mr.specified_logged_in_user_id = 111
+    self.mr.specified_me_user_ids = [222]
+    self.mr.shard_id = 2
+    self.servlet = backendsearch.BackendSearch(
+        'req', 'res', services=self.services)
+    self.mox = mox.Mox()
+
+  def tearDown(self):
+    self.mox.UnsetStubs()
+    self.mox.ResetAll()
+
+  def testHandleRequest_NoResults(self):
+    """Handle the case where the search has no results."""
+    pipeline = testing_helpers.Blank(
+        SearchForIIDs=lambda: None,
+        result_iids=[],
+        search_limit_reached=False,
+        error=None)
+    self.mox.StubOutWithMock(backendsearchpipeline, 'BackendSearchPipeline')
+    backendsearchpipeline.BackendSearchPipeline(
+      self.mr, self.services, 100, ['proj'], 111, [222]
+      ).AndReturn(pipeline)
+    self.mox.ReplayAll()
+
+    json_data = self.servlet.HandleRequest(self.mr)
+    self.mox.VerifyAll()
+    self.assertEqual([], json_data['unfiltered_iids'])
+    self.assertFalse(json_data['search_limit_reached'])
+    self.assertEqual(None, json_data['error'])
+
+  def testHandleRequest_ResultsInOnePagainationPage(self):
+    """Prefetch all result issues and return them."""
+    allowed_iids = [1, 2, 3, 4, 5, 6, 7, 8]
+    pipeline = testing_helpers.Blank(
+        SearchForIIDs=lambda: None,
+        result_iids=allowed_iids,
+        search_limit_reached=False,
+        error=None)
+    self.mox.StubOutWithMock(backendsearchpipeline, 'BackendSearchPipeline')
+    backendsearchpipeline.BackendSearchPipeline(
+      self.mr, self.services, 100, ['proj'], 111, [222]
+      ).AndReturn(pipeline)
+    self.mox.StubOutWithMock(self.services.issue, 'GetIssues')
+    # All issues are prefetched because they fit  on the first pagination page.
+    self.services.issue.GetIssues(self.mr.cnxn, allowed_iids, shard_id=2)
+    self.mox.ReplayAll()
+
+    json_data = self.servlet.HandleRequest(self.mr)
+    self.mox.VerifyAll()
+    self.assertEqual([1, 2, 3, 4, 5, 6, 7, 8], json_data['unfiltered_iids'])
+    self.assertFalse(json_data['search_limit_reached'])
+    self.assertEqual(None, json_data['error'])
+
+  def testHandleRequest_ResultsExceedPagainationPage(self):
+    """Return all result issue IDs, but only prefetch the first page."""
+    self.mr.num = 5
+    pipeline = testing_helpers.Blank(
+        SearchForIIDs=lambda: None,
+        result_iids=[1, 2, 3, 4, 5, 6, 7, 8],
+        search_limit_reached=False,
+        error=None)
+    self.mox.StubOutWithMock(backendsearchpipeline, 'BackendSearchPipeline')
+    backendsearchpipeline.BackendSearchPipeline(
+      self.mr, self.services, 100, ['proj'], 111, [222]
+      ).AndReturn(pipeline)
+    self.mox.StubOutWithMock(self.services.issue, 'GetIssues')
+    # First 5 issues are prefetched because num=5
+    self.services.issue.GetIssues(self.mr.cnxn, [1, 2, 3, 4, 5], shard_id=2)
+    self.mox.ReplayAll()
+
+    json_data = self.servlet.HandleRequest(self.mr)
+    self.mox.VerifyAll()
+    # All are IDs are returned to the frontend.
+    self.assertEqual([1, 2, 3, 4, 5, 6, 7, 8], json_data['unfiltered_iids'])
+    self.assertFalse(json_data['search_limit_reached'])
+    self.assertEqual(None, json_data['error'])
+
+  def testHandleRequest_QueryError(self):
+    """Handle the case where the search has no results."""
+    error = ValueError('Malformed query')
+    pipeline = testing_helpers.Blank(
+        SearchForIIDs=lambda: None,
+        result_iids=[],
+        search_limit_reached=False,
+        error=error)
+    self.mox.StubOutWithMock(backendsearchpipeline, 'BackendSearchPipeline')
+    backendsearchpipeline.BackendSearchPipeline(
+      self.mr, self.services, 100, ['proj'], 111, [222]
+      ).AndReturn(pipeline)
+    self.mox.ReplayAll()
+
+    json_data = self.servlet.HandleRequest(self.mr)
+    self.mox.VerifyAll()
+    self.assertEqual([], json_data['unfiltered_iids'])
+    self.assertFalse(json_data['search_limit_reached'])
+    self.assertEqual(error.message, json_data['error'])