Reland: [ios] Refactored back-forward navigation in CRWSessionController.

ios/web/navigation/crw_session_controller_unittest.mm

 // Copyright 2012 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.
 
 #import "ios/web/navigation/crw_session_controller.h"
 
 #import <Foundation/Foundation.h>
 
 #include <utility>
 
@@ skipping 356 matching lines @@
 
   EXPECT_EQ(1U, [[session_controller_ entries] count]);
   EXPECT_EQ(
       GURL("http://www.url.com/"),
       [session_controller_ URLForSessionAtIndex:0U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:0U],
       [session_controller_ currentEntry]);
 }
 
+// Tests going back from the second and last entry to the first one.
 TEST_F(CRWSessionControllerTest, GoBackFromTheEnd) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url2.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   [session_controller_ goBack];
 
-  EXPECT_EQ(2U, [[session_controller_ entries] count]);
+  ASSERT_EQ(2U, [[session_controller_ entries] count]);
   EXPECT_EQ(
       GURL("http://www.url.com/"),
       [session_controller_ URLForSessionAtIndex:0U]);
   EXPECT_EQ(
       GURL("http://www.url2.com/"),
       [session_controller_ URLForSessionAtIndex:1U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:0U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:1U],
+            [session_controller_ previousEntry]);
 }
 
+// Tests going back twice from the second and last entry to the first one.
 TEST_F(CRWSessionControllerTest, GoBackFromTheBeginning) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url2.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   [session_controller_ goBack];
   [session_controller_ goBack];
 
   EXPECT_EQ(2U, [[session_controller_ entries] count]);
   EXPECT_EQ(
       GURL("http://www.url.com/"),
       [session_controller_ URLForSessionAtIndex:0U]);
   EXPECT_EQ(
       GURL("http://www.url2.com/"),
       [session_controller_ URLForSessionAtIndex:1U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:0U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:1U],
+            [session_controller_ previousEntry]);
 }
 
 TEST_F(CRWSessionControllerTest, GoBackFromTheMiddle) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
@@ skipping 27 matching lines @@
       [session_controller_ URLForSessionAtIndex:1U]);
   EXPECT_EQ(
       GURL("http://www.url3.com/"),
       [session_controller_ URLForSessionAtIndex:2U]);
   EXPECT_EQ(
       GURL("http://www.url4.com/"),
       [session_controller_ URLForSessionAtIndex:3U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:1U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:2U],
+            [session_controller_ previousEntry]);
 }
 
 TEST_F(CRWSessionControllerTest, GoBackAndRemove) {
   [session_controller_
    addPendingEntry:GURL("http://www.url.com")
    referrer:MakeReferrer("http://www.referer.com")
    transition:ui::PAGE_TRANSITION_TYPED
    rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
@@ skipping 34 matching lines @@
 
   [session_controller_ goForward];
 
   EXPECT_EQ(1U, [[session_controller_ entries] count]);
   EXPECT_EQ(
       GURL("http://www.url.com/"),
       [session_controller_ URLForSessionAtIndex:0U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:0U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:0U],
+            [session_controller_ currentEntry]);
 }
 
 TEST_F(CRWSessionControllerTest, GoForewardFromTheEnd) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url2.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   [session_controller_ goForward];
 
   EXPECT_EQ(2U, [[session_controller_ entries] count]);
   EXPECT_EQ(
       GURL("http://www.url.com/"),
       [session_controller_ URLForSessionAtIndex:0U]);
   EXPECT_EQ(
       GURL("http://www.url2.com/"),
       [session_controller_ URLForSessionAtIndex:1U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:1U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:1U],
+            [session_controller_ currentEntry]);
 }
 
 TEST_F(CRWSessionControllerTest, GoForewardFromTheBeginning) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url2.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   [session_controller_ goBack];
   [session_controller_ goForward];
 
   EXPECT_EQ(2U, [[session_controller_ entries] count]);
   EXPECT_EQ(
       GURL("http://www.url.com/"),
       [session_controller_ URLForSessionAtIndex:0U]);
   EXPECT_EQ(
       GURL("http://www.url2.com/"),
       [session_controller_ URLForSessionAtIndex:1U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:1U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:0U],
+            [session_controller_ previousEntry]);
 }
 
 TEST_F(CRWSessionControllerTest, GoForwardFromTheMiddle) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
@@ skipping 28 matching lines @@
       [session_controller_ URLForSessionAtIndex:1U]);
   EXPECT_EQ(
       GURL("http://www.url3.com/"),
       [session_controller_ URLForSessionAtIndex:2U]);
   EXPECT_EQ(
       GURL("http://www.url4.com/"),
       [session_controller_ URLForSessionAtIndex:3U]);
   EXPECT_EQ(
       [[session_controller_ entries] objectAtIndex:2U],
       [session_controller_ currentEntry]);
+  EXPECT_EQ([[session_controller_ entries] objectAtIndex:1U],
+            [session_controller_ previousEntry]);
+}
+
+// Tests going delta, including out of range cases.
+TEST_F(CRWSessionControllerTest, GoDelta) {
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/0")
+                              referrer:MakeReferrer("http://www.example.com/a")
+                            transition:ui::PAGE_TRANSITION_LINK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/redirect")
+                              referrer:MakeReferrer("http://www.example.com/r")
+                            transition:ui::PAGE_TRANSITION_IS_REDIRECT_MASK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/1")
+                              referrer:MakeReferrer("http://www.example.com/b")
+                            transition:ui::PAGE_TRANSITION_LINK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/2")
+                              referrer:MakeReferrer("http://www.example.com/c")
+                            transition:ui::PAGE_TRANSITION_LINK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/redirect")
+                              referrer:MakeReferrer("http://www.example.com/r")
+                            transition:ui::PAGE_TRANSITION_IS_REDIRECT_MASK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(3, [session_controller_ previousNavigationIndex]);
+  NSArray* entries = [session_controller_ entries];
+  ASSERT_EQ(5U, entries.count);
+
+  // Try going forward, which should not be possible.
+  EXPECT_FALSE([session_controller_ canGoDelta:1]);
+  [session_controller_ goDelta:1];
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(3, [session_controller_ previousNavigationIndex]);
+
+  // Try going back 3 entries, which should not be possible as there are only 2
+  // non-redirect entries.
+  EXPECT_FALSE([session_controller_ canGoDelta:-3]);
+  [session_controller_ goDelta:-3];
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(3, [session_controller_ previousNavigationIndex]);
+  [session_controller_ goToEntry:entries[4]];
+
+  // Go back 2 entries.
+  EXPECT_TRUE([session_controller_ canGoDelta:-2]);
+  [session_controller_ goDelta:-2];
+  ASSERT_EQ(1, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(4, [session_controller_ previousNavigationIndex]);
+
+  // Try going back 1 entry which should not be possible, because back entry had
+  // redirect response.
+  EXPECT_FALSE([session_controller_ canGoDelta:-1]);
+  [session_controller_ goDelta:-1];
+  ASSERT_EQ(1, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(4, [session_controller_ previousNavigationIndex]);
+
+  // Try going forward 3 entries which should not be possible, because there are
+  // only 2 non-redirect entries in forward entries.
+  EXPECT_FALSE([session_controller_ canGoDelta:3]);
+  [session_controller_ goDelta:3];
+  ASSERT_EQ(1, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(4, [session_controller_ previousNavigationIndex]);
+  [session_controller_ goToEntry:entries[1]];
+
+  // Go forward 2 entries.
+  EXPECT_TRUE([session_controller_ canGoDelta:2]);
+  [session_controller_ goDelta:2];
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(1, [session_controller_ previousNavigationIndex]);
+
+  // Now add a transient entry and go back 2 entries.
+  [session_controller_ addTransientEntryWithURL:GURL("http://www.example.com")];
+  EXPECT_TRUE([session_controller_ canGoDelta:-2]);
+  [session_controller_ goDelta:-2];
+  ASSERT_EQ(2, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(4, [session_controller_ previousNavigationIndex]);
+
+  // Try going back 2 entries which should not be possible, because there is
+  // only one non-redirect back entry.
+  EXPECT_FALSE([session_controller_ canGoDelta:-2]);
+  [session_controller_ goDelta:-2];
+  ASSERT_EQ(2, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(4, [session_controller_ previousNavigationIndex]);
+  [session_controller_ goToEntry:entries[2]];
+
+  // Go back 1 entry.
+  EXPECT_TRUE([session_controller_ canGoDelta:-1]);
+  [session_controller_ goDelta:-1];
+  ASSERT_EQ(1, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(2, [session_controller_ previousNavigationIndex]);
+
+  // Go forward 1 entry.
+  EXPECT_TRUE([session_controller_ canGoDelta:1]);
+  [session_controller_ goDelta:1];
+  ASSERT_EQ(2, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(1, [session_controller_ previousNavigationIndex]);
 }
 
 TEST_F(CRWSessionControllerTest, CanGoBackWithoutCommitedEntry) {
   EXPECT_FALSE([session_controller_ canGoBack]);
+  EXPECT_FALSE([session_controller_ canGoDelta:-1]);
 }
 
 // Tests that |canGoBack| returns NO if there is a transient entry, but no
 // committed entries.
 TEST_F(CRWSessionControllerTest, CanGoBackWithTransientEntry) {
   [session_controller_ addTransientEntryWithURL:GURL("http://www.url.com")];
 
   EXPECT_FALSE([session_controller_ canGoBack]);
 }
 
@@ skipping 12 matching lines @@
 
 TEST_F(CRWSessionControllerTest, CanGoBackWithSingleCommitedEntry) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   EXPECT_FALSE([session_controller_ canGoBack]);
+  EXPECT_FALSE([session_controller_ canGoDelta:-1]);
 }
 
 TEST_F(CRWSessionControllerTest, CanGoBackWithMultipleCommitedEntries) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url1.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url2.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   EXPECT_TRUE([session_controller_ canGoBack]);
+  EXPECT_TRUE([session_controller_ canGoDelta:-1]);
 
   [session_controller_ goBack];
   EXPECT_TRUE([session_controller_ canGoBack]);
+  EXPECT_TRUE([session_controller_ canGoDelta:-1]);
 
   [session_controller_ goBack];
   EXPECT_FALSE([session_controller_ canGoBack]);
+  EXPECT_FALSE([session_controller_ canGoDelta:-1]);
 
   [session_controller_ goBack];
   EXPECT_FALSE([session_controller_ canGoBack]);
+  EXPECT_FALSE([session_controller_ canGoDelta:-1]);
 
   [session_controller_ goForward];
   EXPECT_TRUE([session_controller_ canGoBack]);
+  EXPECT_TRUE([session_controller_ canGoDelta:-1]);
+}
+
+// Tests that going forward is not possible if there is a pending entry.
+TEST_F(CRWSessionControllerTest, CanGoForwardWithPendingEntry) {
+  [session_controller_ addPendingEntry:GURL("http://www.url.com")
+                              referrer:MakeReferrer("http://www.referer.com")
+                            transition:ui::PAGE_TRANSITION_TYPED
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.url1.com")
+                              referrer:MakeReferrer("http://www.referer.com")
+                            transition:ui::PAGE_TRANSITION_TYPED
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ goBack];
+  [session_controller_ addPendingEntry:GURL("http://www.url2.com")
+                              referrer:MakeReferrer("http://www.referer.com")
+                            transition:ui::PAGE_TRANSITION_TYPED
+                     rendererInitiated:NO];
+
+  // Pending entry should not allow going forward.
+  EXPECT_FALSE([session_controller_ canGoForward]);
+  EXPECT_FALSE([session_controller_ canGoDelta:1]);
 }
 
 TEST_F(CRWSessionControllerTest, CanGoForwardWithoutCommitedEntry) {
   EXPECT_FALSE([session_controller_ canGoForward]);
+  EXPECT_FALSE([session_controller_ canGoDelta:1]);
 }
 
 TEST_F(CRWSessionControllerTest, CanGoForwardWithSingleCommitedEntry) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   EXPECT_FALSE([session_controller_ canGoForward]);
+  EXPECT_FALSE([session_controller_ canGoDelta:1]);
 }
 
 TEST_F(CRWSessionControllerTest, CanGoForwardWithMultipleCommitedEntries) {
   [session_controller_
         addPendingEntry:GURL("http://www.url.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url1.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
   [session_controller_
         addPendingEntry:GURL("http://www.url2.com")
                referrer:MakeReferrer("http://www.referer.com")
              transition:ui::PAGE_TRANSITION_TYPED
       rendererInitiated:NO];
   [session_controller_ commitPendingEntry];
 
   EXPECT_FALSE([session_controller_ canGoForward]);
+  EXPECT_FALSE([session_controller_ canGoDelta:1]);
 
   [session_controller_ goBack];
   EXPECT_TRUE([session_controller_ canGoForward]);
+  EXPECT_TRUE([session_controller_ canGoDelta:1]);
 
   [session_controller_ goBack];
   EXPECT_TRUE([session_controller_ canGoForward]);
+  EXPECT_TRUE([session_controller_ canGoDelta:1]);
 
   [session_controller_ goForward];
   EXPECT_TRUE([session_controller_ canGoForward]);
+  EXPECT_TRUE([session_controller_ canGoDelta:1]);
 
   [session_controller_ goForward];
   EXPECT_FALSE([session_controller_ canGoForward]);
+  EXPECT_FALSE([session_controller_ canGoDelta:1]);
 }
 
 // Helper to create a NavigationItem. Caller is responsible for freeing
 // the memory.
 web::NavigationItem* CreateNavigationItem(const std::string& url,
                                           const std::string& referrer,
                                           NSString* title) {
   web::Referrer referrer_object(GURL(referrer),
                                 web::ReferrerPolicyDefault);
   web::NavigationItemImpl* navigation_item = new web::NavigationItemImpl();
@@ skipping 278 matching lines @@
   EXPECT_EQ(1, session_controller_.get().currentNavigationIndex);
 
   // Remove an entry and attempt to go it. Ensure it outlives the removal.
   base::scoped_nsobject<CRWSessionEntry> entry3(
       [[session_controller_.get().entries objectAtIndex:3] retain]);
   [session_controller_ removeEntryAtIndex:3];
   [session_controller_ goToEntry:entry3];
   EXPECT_EQ(1, session_controller_.get().currentNavigationIndex);
 }
 
+// Tests -[CRWSessionController indexOfEntryForDelta:] API for positive,
+// negative and zero delta. Tested session controller will have redirect entries
+// to make sure they are appropriately skipped.
+TEST_F(CRWSessionControllerTest, IndexOfEntryForDelta) {
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/0")
+                              referrer:MakeReferrer("http://www.example.com/a")
+                            transition:ui::PAGE_TRANSITION_LINK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/redirect")
+                              referrer:MakeReferrer("http://www.example.com/r")
+                            transition:ui::PAGE_TRANSITION_IS_REDIRECT_MASK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/1")
+                              referrer:MakeReferrer("http://www.example.com/b")
+                            transition:ui::PAGE_TRANSITION_LINK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/2")
+                              referrer:MakeReferrer("http://www.example.com/c")
+                            transition:ui::PAGE_TRANSITION_LINK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  [session_controller_ addPendingEntry:GURL("http://www.example.com/redirect")
+                              referrer:MakeReferrer("http://www.example.com/r")
+                            transition:ui::PAGE_TRANSITION_IS_REDIRECT_MASK
+                     rendererInitiated:NO];
+  [session_controller_ commitPendingEntry];
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  ASSERT_EQ(5U, [[session_controller_ entries] count]);
+
+  // Go to entry at index 1 and test API from that state.
+  NSArray* entries = [session_controller_ entries];
+  [session_controller_ goToEntry:entries[1]];
+  ASSERT_EQ(1, [session_controller_ currentNavigationIndex]);
+  EXPECT_EQ(-1, [session_controller_ indexOfEntryForDelta:-1]);
+  EXPECT_EQ(-2, [session_controller_ indexOfEntryForDelta:-2]);
+  EXPECT_EQ(2, [session_controller_ indexOfEntryForDelta:1]);
+  EXPECT_EQ(4, [session_controller_ indexOfEntryForDelta:2]);
+  EXPECT_EQ(5, [session_controller_ indexOfEntryForDelta:3]);
+
+  // Go to entry at index 2 and test API from that state.
+  [session_controller_ goToEntry:entries[2]];
+  ASSERT_EQ(2, [session_controller_ currentNavigationIndex]);
+  EXPECT_EQ(1, [session_controller_ indexOfEntryForDelta:-1]);
+  EXPECT_EQ(-1, [session_controller_ indexOfEntryForDelta:-2]);
+  EXPECT_EQ(4, [session_controller_ indexOfEntryForDelta:1]);
+  EXPECT_EQ(5, [session_controller_ indexOfEntryForDelta:2]);
+
+  // Go to entry at index 4 and test API from that state.
+  [session_controller_ goToEntry:entries[4]];
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  EXPECT_EQ(2, [session_controller_ indexOfEntryForDelta:-1]);
+  EXPECT_EQ(1, [session_controller_ indexOfEntryForDelta:-2]);
+  EXPECT_EQ(5, [session_controller_ indexOfEntryForDelta:1]);
+  EXPECT_EQ(6, [session_controller_ indexOfEntryForDelta:2]);
+
+  // Now try with existing transient entry.
+  [session_controller_ addTransientEntryWithURL:GURL("http://www.example.com")];
+  ASSERT_EQ(5U, [[session_controller_ entries] count]);
+  ASSERT_EQ(4, [session_controller_ currentNavigationIndex]);
+  EXPECT_EQ(4, [session_controller_ indexOfEntryForDelta:-1]);
+  EXPECT_EQ(2, [session_controller_ indexOfEntryForDelta:-2]);
+  EXPECT_EQ(1, [session_controller_ indexOfEntryForDelta:-3]);
+  EXPECT_EQ(5, [session_controller_ indexOfEntryForDelta:1]);
+  EXPECT_EQ(6, [session_controller_ indexOfEntryForDelta:2]);
+}
+
 }  // anonymous namespace