From 7e66d427e9d739051cf915c3adb463ccc4de22bb Mon Sep 17 00:00:00 2001
From: Nate Chapin <japhet@chromium.org>
Date: Wed, 18 Oct 2023 08:33:19 +0000
Subject: [PATCH] Bug 1856741 [wpt PR 42228] - Make
 navigation-api/navigation-methods/ resilient to starting with extra
 NavigationHistoryEntries, a=testonly

Automatic update from web-platform-tests
Make navigation-api/navigation-methods/ resilient to starting with extra NavigationHistoryEntries

When WPT are run in-browser or via wptrunner, there may be additional
session history entries when the test starts, so the tests shouldn't
assume that they start with navigation.entries().length == 1 or
navigation.currentEntry.index == 0.

This is a workaround for https://github.com/web-platform-tests/wpt/issues/33590.

Change-Id: I406474b33d9c17b682d5d54fc88f5c677bc3d3ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4904062
Reviewed-by: Domenic Denicola <domenic@chromium.org>
Commit-Queue: Nate Chapin <japhet@chromium.org>
Auto-Submit: Nate Chapin <japhet@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1204876}

--

wpt-commits: e1f2e7c0dd66323b85a8cb90182066ed3e6cef9f
wpt-pr: 42228
---
 .../back-forward-multiple-frames.html         | 22 ++++++++++---------
 .../navigation-methods/disambigaute-back.html | 12 +++++-----
 .../disambigaute-forward.html                 | 16 ++++++++------
 ...disambigaute-traverseTo-back-multiple.html | 12 +++++-----
 ...ambigaute-traverseTo-forward-multiple.html | 16 ++++++++------
 .../forward-to-pruned-entry.html              | 12 +++++-----
 .../navigate-history-push-not-loaded.html     |  7 +++---
 .../navigate-history-push-same-url.html       |  8 ++++---
 .../navigate-replace-cross-document.html      |  3 ++-
 .../navigate-replace-same-document.html       |  3 ++-
 .../back-forward-out-of-bounds.html           | 15 +++++++------
 .../return-value/back-intercept-rejected.html |  6 +++--
 .../return-value/back-intercept.html          |  6 +++--
 .../navigation-methods/return-value/back.html |  6 +++--
 .../forward-intercept-rejected.html           |  6 +++--
 .../return-value/forward-intercept.html       |  6 +++--
 .../return-value/forward.html                 |  6 +++--
 .../navigate-intercept-interrupted.html       |  8 ++++---
 ...avigate-interrupted-within-onnavigate.html |  6 +++--
 .../return-value/navigate-interrupted.html    |  8 ++++---
 .../return-value/traverseTo-current.html      |  4 ++--
 .../traverseTo-intercept-rejected.html        |  6 +++--
 .../return-value/traverseTo-intercept.html    |  6 +++--
 .../return-value/traverseTo.html              |  6 +++--
 .../traverseTo-after-adding-iframe.html       |  4 ++--
 .../traverseTo-multiple-steps.html            | 14 +++++++-----
 ...traverseTo-navigates-multiple-iframes.html |  3 ++-
 .../traverseTo-same-document.html             | 20 +++++++++--------
 28 files changed, 147 insertions(+), 100 deletions(-)

diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/back-forward-multiple-frames.html b/testing/web-platform/tests/navigation-api/navigation-methods/back-forward-multiple-frames.html
index 738bfd37dcc72..6c30987f7598d 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/back-forward-multiple-frames.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/back-forward-multiple-frames.html
@@ -6,20 +6,22 @@
 promise_test(async t => {
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
   // Step 1
-  assert_equals(navigation.entries().length, 1, "step 1 outer entries() length");
+  assert_equals(navigation.entries().length, start_length, "step 1 outer entries() length");
   assert_equals(i.contentWindow.navigation.entries().length, 1, "step 1 iframe entries() length");
   await navigation.navigate("#top").committed;
   // Step 2: iframe at initial entry, top on second entry
-  assert_equals(navigation.entries().length, 2, "step 2 outer entries() length");
+  assert_equals(navigation.entries().length, start_length+1, "step 2 outer entries() length");
   assert_equals(i.contentWindow.navigation.entries().length, 1, "step 2 iframe entries() length");
   await i.contentWindow.navigation.navigate("#iframe").committed;
 
   // Step 3: Both windows on second entry.
-  assert_equals(navigation.entries().length, 2, "step 3 outer entries() length");
+  assert_equals(navigation.entries().length, start_length+1, "step 3 outer entries() length");
   assert_equals(i.contentWindow.navigation.entries().length, 2, "step 3 iframe entries() length");
-  assert_equals(navigation.currentEntry.index, 1, "step 3 outer index");
+  assert_equals(navigation.currentEntry.index, start_index+1, "step 3 outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 1, "step 1 iframe index");
 
   // NOTE: the order of navigation in the two windows is not guaranteed; we need to wait for both.
@@ -29,7 +31,7 @@
     i.contentWindow.navigation.back().committed,
     new Promise(resolve => i.contentWindow.onpopstate = resolve)
   ]);
-  assert_equals(navigation.currentEntry.index, 1, "after iframe back() outer index");
+  assert_equals(navigation.currentEntry.index, start_index+1, "after iframe back() outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0, "after iframe back() iframe index");
 
   // Going forward in iframe should go 2->3
@@ -37,7 +39,7 @@
     i.contentWindow.navigation.forward().commited,
     new Promise(resolve => i.contentWindow.onpopstate = resolve)
   ]);
-  assert_equals(navigation.currentEntry.index, 1, "after iframe forward() outer index");
+  assert_equals(navigation.currentEntry.index, start_index+1, "after iframe forward() outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 1, "after iframe forward() iframe index");
 
   // Going back in top should go 3->1 (navigating both windows).
@@ -45,7 +47,7 @@
     navigation.back().commited,
     new Promise(resolve => i.contentWindow.onpopstate = resolve)
   ]);
-  assert_equals(navigation.currentEntry.index, 0, "after outer back() outer index");
+  assert_equals(navigation.currentEntry.index, start_index, "after outer back() outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0, "after outer back() iframe index");
 
   // Next two should not navigate the iframe
@@ -54,13 +56,13 @@
   // Going forward in top should go 1->2 (navigating top only)
   await navigation.forward().committed;
   await new Promise(resolve => t.step_timeout(resolve, 0));
-  assert_equals(navigation.currentEntry.index, 1, "after outer forward() outer index");
+  assert_equals(navigation.currentEntry.index, start_index+1, "after outer forward() outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0, "after outer forward() iframe index");
 
   // Going back in top should go 2->1
   await navigation.back().committed;
   await new Promise(resolve => t.step_timeout(resolve, 0));
-  assert_equals(navigation.currentEntry.index, 0, "after outer second back() outer index");
+  assert_equals(navigation.currentEntry.index, start_index, "after outer second back() outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0, "after outer second back() iframe index");
 
   // Going forward in iframe should go 1->3 (navigating both windows)
@@ -68,7 +70,7 @@
     i.contentWindow.navigation.forward().commited,
     new Promise(resolve => i.contentWindow.onpopstate = resolve)
   ]);
-  assert_equals(navigation.currentEntry.index, 1, "after iframe second forward() outer index");
+  assert_equals(navigation.currentEntry.index, start_index+1, "after iframe second forward() outer index");
   assert_equals(i.contentWindow.navigation.currentEntry.index, 1, "after iframe second forward() iframe index");
 }, "navigation.back() and navigation.forward() can navigate multiple frames");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-back.html b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-back.html
index d44d435896dd8..a42000ca5fc9c 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-back.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-back.html
@@ -4,18 +4,20 @@
 <iframe id="i" src="/common/blank.html"></iframe>
 <script>
 async_test(t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   window.onload = () => t.step_timeout(() => {
-    assert_equals(navigation.entries().length, 1);
+    assert_equals(navigation.entries().length, start_length);
     assert_equals(i.contentWindow.navigation.entries().length, 1);
     navigation.navigate("#top");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length+1);
     assert_equals(i.contentWindow.navigation.entries().length, 1);
     i.contentWindow.navigation.navigate("#1");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length+1);
     assert_equals(i.contentWindow.navigation.entries().length, 2);
-    assert_equals(navigation.currentEntry.index, 1);
+    assert_equals(navigation.currentEntry.index, start_index+1);
     assert_equals(i.contentWindow.navigation.currentEntry.index, 1);
     assert_true(navigation.canGoBack);
     assert_true(i.contentWindow.navigation.canGoBack);
@@ -24,7 +26,7 @@
     // previous key. Navigate to the nearest one (which navigates the iframe
     // but not the top window).
     i.contentWindow.navigation.back().committed.then(t.step_func_done(() => {
-      assert_equals(navigation.currentEntry.index, 1);
+      assert_equals(navigation.currentEntry.index, start_index+1);
       assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
     }));
   }, 0);
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-forward.html b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-forward.html
index e252e30994103..3062cb0bebfc6 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-forward.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-forward.html
@@ -4,33 +4,35 @@
 <iframe id="i" src="/common/blank.html"></iframe>
 <script>
 async_test(t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   window.onload = () => t.step_timeout(() => {
-    assert_equals(navigation.entries().length, 1);
+    assert_equals(navigation.entries().length, start_length);
     assert_equals(i.contentWindow.navigation.entries().length, 1);
     navigation.navigate("#top");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length+1);
     assert_equals(i.contentWindow.navigation.entries().length, 1);
     i.contentWindow.navigation.navigate("#1");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length+1);
     assert_equals(i.contentWindow.navigation.entries().length, 2);
-    assert_equals(navigation.currentEntry.index, 1);
+    assert_equals(navigation.currentEntry.index, start_index+1);
     assert_equals(i.contentWindow.navigation.currentEntry.index, 1);
     assert_true(navigation.canGoBack);
     assert_true(i.contentWindow.navigation.canGoBack);
 
     i.contentWindow.navigation.back().committed.then(t.step_func(() => {
-      assert_equals(navigation.currentEntry.index, 1);
+      assert_equals(navigation.currentEntry.index, start_index+1);
       assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
       navigation.back().committed.then(t.step_func(() => {
-        assert_equals(navigation.currentEntry.index, 0);
+        assert_equals(navigation.currentEntry.index, start_index);
         assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
         // There are 2 joint session history entries containing the top window's
         // final key. Navigate to the nearest one (which navigates only the
         // top window).
         navigation.forward().committed.then(t.step_func_done(() => {
-          assert_equals(navigation.currentEntry.index, 1);
+          assert_equals(navigation.currentEntry.index, start_index+1);
           assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
         }));
       }));
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-back-multiple.html b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-back-multiple.html
index 03a8eb10edeb8..7ecfc01b3fce1 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-back-multiple.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-back-multiple.html
@@ -4,21 +4,23 @@
 <iframe id="i" src="/common/blank.html"></iframe>
 <script>
 async_test(t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   window.onload = () => t.step_timeout(() => {
-    assert_equals(navigation.entries().length, 1);
+    assert_equals(navigation.entries().length, start_length);
     assert_equals(i.contentWindow.navigation.entries().length, 1);
     navigation.navigate("#top");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length+1);
     assert_equals(i.contentWindow.navigation.entries().length, 1);
 
     let iframe_initial_key = i.contentWindow.navigation.currentEntry.key;
     i.contentWindow.navigation.navigate("#1");
     i.contentWindow.navigation.navigate("#2");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length+1);
     assert_equals(i.contentWindow.navigation.entries().length, 3);
-    assert_equals(navigation.currentEntry.index, 1);
+    assert_equals(navigation.currentEntry.index, start_index+1);
     assert_equals(i.contentWindow.navigation.currentEntry.index, 2);
     assert_true(navigation.canGoBack);
     assert_true(i.contentWindow.navigation.canGoBack);
@@ -27,7 +29,7 @@
     // initial key.  Navigate to the nearest one (which navigates the iframe
     // but not the top window).
     i.contentWindow.navigation.traverseTo(iframe_initial_key).committed.then(t.step_func_done(() => {
-      assert_equals(navigation.currentEntry.index, 1);
+      assert_equals(navigation.currentEntry.index, start_index+1);
       assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
     }));
   }, 0);
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-forward-multiple.html b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-forward-multiple.html
index f8e78c4b1d951..92f23f0acff9e 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-forward-multiple.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/disambigaute-traverseTo-forward-multiple.html
@@ -4,36 +4,38 @@
 <iframe id="i" src="/common/blank.html"></iframe>
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
-  assert_equals(navigation.entries().length, 1);
+  assert_equals(navigation.entries().length, start_length);
   assert_equals(i.contentWindow.navigation.entries().length, 1);
   let initial_key = navigation.currentEntry.key;
   await navigation.navigate("#top1").committed;
   await navigation.navigate("#top2").committed;
-  assert_equals(navigation.entries().length, 3);
+  assert_equals(navigation.entries().length, start_length+2);
   assert_equals(i.contentWindow.navigation.entries().length, 1);
   await i.contentWindow.navigation.navigate("#1").committed;
-  assert_equals(navigation.entries().length, 3);
+  assert_equals(navigation.entries().length, start_length+2);
   assert_equals(i.contentWindow.navigation.entries().length, 2);
-  assert_equals(navigation.currentEntry.index, 2);
+  assert_equals(navigation.currentEntry.index, start_index+2);
   assert_equals(i.contentWindow.navigation.currentEntry.index, 1);
   assert_true(navigation.canGoBack);
   assert_true(i.contentWindow.navigation.canGoBack);
   let final_key = navigation.currentEntry.key;
 
   await i.contentWindow.navigation.back().committed;
-  assert_equals(navigation.currentEntry.index, 2);
+  assert_equals(navigation.currentEntry.index, start_index+2);
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
   await navigation.traverseTo(initial_key).committed;
-  assert_equals(navigation.currentEntry.index, 0);
+  assert_equals(navigation.currentEntry.index, start_index);
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
   // There are 2 joint session history entries containing the top window's
   // final key. Navigate to the nearest one (which navigates only the
   // top window).
   await navigation.traverseTo(final_key).committed;
-  assert_equals(navigation.currentEntry.index, 2);
+  assert_equals(navigation.currentEntry.index, start_index+2);
   assert_equals(i.contentWindow.navigation.currentEntry.index, 0);
 }, "navigation.traverseTo() goes to the nearest entry when going forward");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/forward-to-pruned-entry.html b/testing/web-platform/tests/navigation-api/navigation-methods/forward-to-pruned-entry.html
index 05f70c5c2dccb..18b30c620d59c 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/forward-to-pruned-entry.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/forward-to-pruned-entry.html
@@ -3,13 +3,15 @@
 <script src="/resources/testharnessreport.js"></script>
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
   await navigation.navigate("#foo").finished;
-  assert_equals(navigation.entries().length, 2);
+  assert_equals(navigation.entries().length, start_length+1);
   await navigation.back().finished;
-  assert_equals(navigation.currentEntry.index, 0);
+  assert_equals(navigation.currentEntry.index, start_index);
 
   // Traverse forward then immediately do a same-document push. This will
   // truncate the back forward list, and by the time the traverse commits, the
@@ -19,15 +21,15 @@
   navigation.onnavigateerror = t.unreached_func("navigateerror should not fire");
   let forward_value = navigation.forward();
   await navigation.navigate("#clobber").finished;
-  assert_equals(navigation.currentEntry.index, 1);
+  assert_equals(navigation.currentEntry.index, start_index+1);
   await promise_rejects_dom(t, "AbortError", forward_value.committed);
   await promise_rejects_dom(t, "AbortError", forward_value.finished);
 
   // This leaves navigation.entries() in a consistent state where traversing
   // back and forward still works.
   await navigation.back().finished;
-  assert_equals(navigation.currentEntry.index, 0);
+  assert_equals(navigation.currentEntry.index, start_index);
   await navigation.forward().finished;
-  assert_equals(navigation.currentEntry.index, 1);
+  assert_equals(navigation.currentEntry.index, start_index+1);
 }, "If forward pruning clobbers the target of a traverse, abort");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-not-loaded.html b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-not-loaded.html
index c1ecdaeeafdfb..f919417332559 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-not-loaded.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-not-loaded.html
@@ -5,8 +5,9 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Purposefully do not wait until after the load event (unlike some sibling tests).
-  assert_equals(navigation.entries().length, 1);
   assert_equals(document.readyState, "loading", "Document must not have loaded yet");
 
   let navigateEventType;
@@ -14,7 +15,7 @@
 
   await navigation.navigate("#1", { history: "push" }).finished;
   assert_equals(navigateEventType, "push");
-  assert_equals(navigation.entries().length, 2);
-  assert_equals(navigation.currentEntry.index, 1);
+  assert_equals(navigation.entries().length, start_length+1);
+  assert_equals(navigation.currentEntry.index, start_index+1);
 }, "navigate() with history: 'push' in a document that has not yet had its load event");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-same-url.html b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-same-url.html
index 339e8c3056bb2..a81215f7d46a3 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-same-url.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-history-push-same-url.html
@@ -5,10 +5,12 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation due to onload not having completed.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
-  assert_equals(navigation.entries().length, 1);
+  assert_equals(navigation.entries().length, start_length);
 
 
   let navigateEventType;
@@ -20,7 +22,7 @@
 
   await navigation.navigate(location.href, { history: "push" }).finished;
   assert_equals(navigateEventType, "push");
-  assert_equals(navigation.entries().length, 2);
-  assert_equals(navigation.currentEntry.index, 1);
+  assert_equals(navigation.entries().length, start_length+1);
+  assert_equals(navigation.currentEntry.index, start_index+1);
 }, "navigate() to the current URL with history: 'push' and intercept so it remains same-document");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-cross-document.html b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-cross-document.html
index 7f016babe6bc7..0a36e25970fd1 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-cross-document.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-cross-document.html
@@ -7,6 +7,7 @@
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation (which would defeat the point of the test).
   window.onload = () => t.step_timeout(() => {
+    let start_length = navigation.entries().length;
     let start_history_length = history.length;
     let start_entry_top = navigation.currentEntry;
     let start_entry_iframe_id = i.contentWindow.navigation.currentEntry.id;
@@ -16,7 +17,7 @@
     i.onload = t.step_func_done(() => {
       assert_equals(history.length, start_history_length);
 
-      assert_equals(navigation.entries().length, 1);
+      assert_equals(navigation.entries().length, start_length);
       assert_equals(navigation.currentEntry, start_entry_top);
 
       assert_equals(i.contentWindow.navigation.entries().length, 1);
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-same-document.html b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-same-document.html
index 0d8493b788240..943ab377654b1 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-same-document.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/navigate-replace-same-document.html
@@ -6,6 +6,7 @@
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   window.onload = () => t.step_timeout(t.step_func_done(async () => {
+    let start_length = navigation.entries().length;
     let start_history_length = history.length;
     let key1 = navigation.currentEntry.key;
     await navigation.navigate("#1").committed;
@@ -14,7 +15,7 @@
     await navigation.navigate("#2", { history: "replace" }).committed;
     let key3 = navigation.currentEntry.key;
     assert_equals(key2, key3);
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length + 1);
     assert_equals(history.length, start_history_length + 1);
   }), 0);
 }, "navigate() with history: 'replace' option");
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-forward-out-of-bounds.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-forward-out-of-bounds.html
index 015c090bf97e5..ac6d901ba52a9 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-forward-out-of-bounds.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-forward-out-of-bounds.html
@@ -2,15 +2,16 @@
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <script src="resources/helpers.js"></script>
-
+<iframe id="i" src="/common/blank.html"></iframe>
 <script>
 promise_test(async t => {
-  assert_equals(navigation.entries().length, 1);
-  assert_equals(navigation.entries()[0], navigation.currentEntry);
-  assert_false(navigation.canGoBack);
-  assert_false(navigation.canGoForward);
+  await new Promise(resolve => window.onload = resolve);
+  assert_equals(i.contentWindow.navigation.entries().length, 1);
+  assert_equals(i.contentWindow.navigation.entries()[0], i.contentWindow.navigation.currentEntry);
+  assert_false(i.contentWindow.navigation.canGoBack);
+  assert_false(i.contentWindow.navigation.canGoForward);
 
-  await assertBothRejectDOM(t, navigation.back(), "InvalidStateError");
-  await assertBothRejectDOM(t, navigation.forward(), "InvalidStateError");
+  await assertBothRejectDOM(t, i.contentWindow.navigation.back(), "InvalidStateError", i.contentWindow);
+  await assertBothRejectDOM(t, i.contentWindow.navigation.forward(), "InvalidStateError", i.contentWindow);
 }, "back() and forward() out of bounds");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept-rejected.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept-rejected.html
index 9d4238087ff50..013ebf1e1e3df 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept-rejected.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept-rejected.html
@@ -5,14 +5,16 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept.html
index 2654045c2b008..1db2f870d8dce 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back-intercept.html
@@ -5,14 +5,16 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back.html
index a2b13db901bfa..5521de25b7950 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/back.html
@@ -5,14 +5,16 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept-rejected.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept-rejected.html
index 9e86dcca19760..9d5318a260d77 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept-rejected.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept-rejected.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -12,8 +14,8 @@
   location.href = "#1";
   await navigation.back().committed;
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept.html
index ce4ab3217070a..3c52119745411 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward-intercept.html
@@ -5,14 +5,16 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward.html
index 36bdba8daafd8..5ba58f2c8ea19 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/forward.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -12,8 +14,8 @@
   location.href = "#1";
   await navigation.back().committed;
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-intercept-interrupted.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-intercept-interrupted.html
index 36403c892c6c9..7f661b80b6d49 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-intercept-interrupted.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-intercept-interrupted.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -14,10 +16,10 @@
   const result1 = navigation.navigate("#1");
   const result2 = navigation.navigate("#2");
 
-  assert_equals(navigation.entries().length, 3);
-  assert_array_equals(navigation.entries().map(e => (new URL(e.url)).hash), ["", "#1", "#2"]);
+  assert_equals(navigation.entries().length, start_length + 2);
+  assert_array_equals(navigation.entries().slice(start_index).map(e => (new URL(e.url)).hash), ["", "#1", "#2"]);
 
-  await assertCommittedFulfillsFinishedRejectsDOM(t, result1, navigation.entries()[1], "AbortError");
+  await assertCommittedFulfillsFinishedRejectsDOM(t, result1, navigation.entries()[start_index + 1], "AbortError");
   await assertBothFulfill(t, result2, navigation.currentEntry);
 }, "interrupted navigate() promises with intercept()");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted-within-onnavigate.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted-within-onnavigate.html
index 3db02c6931e41..249a7df69c2ff 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted-within-onnavigate.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted-within-onnavigate.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -19,8 +21,8 @@
 
   const result1 = navigation.navigate("#1", { info: 1 });
 
-  assert_equals(navigation.entries().length, 2);
-  assert_array_equals(navigation.entries().map(e => (new URL(e.url)).hash), ["", "#2"]);
+  assert_equals(navigation.entries().length, start_length + 1);
+  assert_array_equals(navigation.entries().slice(start_index).map(e => (new URL(e.url)).hash), ["", "#2"]);
 
   await assertBothRejectDOM(t, result1, "AbortError");
   await assertBothFulfill(t, result2, navigation.currentEntry);
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted.html
index 2c928254e0b64..d1ade5b423da7 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/navigate-interrupted.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -12,10 +14,10 @@
   const result1 = navigation.navigate("#1");
   const result2 = navigation.navigate("#2");
 
-  assert_equals(navigation.entries().length, 3);
-  assert_array_equals(navigation.entries().map(e => (new URL(e.url)).hash), ["", "#1", "#2"]);
+  assert_equals(navigation.entries().length, start_length + 2);
+  assert_array_equals(navigation.entries().slice(start_index).map(e => (new URL(e.url)).hash), ["", "#1", "#2"]);
 
-  await assertCommittedFulfillsFinishedRejectsDOM(t, result1, navigation.entries()[1], "AbortError");
+  await assertCommittedFulfillsFinishedRejectsDOM(t, result1, navigation.entries()[start_index + 1], "AbortError");
   await assertBothFulfill(t, result2, navigation.currentEntry);
 }, "interrupted navigate() promises");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-current.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-current.html
index 212fe992cf774..3942faf77fb3b 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-current.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-current.html
@@ -5,13 +5,13 @@
 
 <script>
 promise_test(async t => {
-  assert_equals(navigation.entries().length, 1);
+  let start_length = navigation.entries().length;
   const entry = navigation.currentEntry;
 
   const result = navigation.traverseTo(navigation.currentEntry.key);
   await assertBothFulfill(t, result, entry);
 
-  assert_equals(navigation.entries().length, 1);
+  assert_equals(navigation.entries().length, start_length);
   assert_equals(navigation.currentEntry, entry);
 }, "traverseTo() with current key");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept-rejected.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept-rejected.html
index f934eae5d4c1a..f39913e05b239 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept-rejected.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept-rejected.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -13,8 +15,8 @@
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept.html
index a4cb4e711d8c9..e5baf8b1417fc 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo-intercept.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -13,8 +15,8 @@
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length + 1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo.html b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo.html
index 8e00f5ba918cd..5270bbb411df8 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/return-value/traverseTo.html
@@ -5,6 +5,8 @@
 
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -13,8 +15,8 @@
 
   location.href = "#1";
 
-  assert_equals(navigation.entries().length, 2);
-  const [entry0, entry1] = navigation.entries();
+  assert_equals(navigation.entries().length, start_length+1);
+  const [entry0, entry1] = navigation.entries().slice(start_index);
   assert_equals((new URL(entry0.url)).hash, "");
   assert_equals((new URL(entry1.url)).hash, "#1");
 
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-after-adding-iframe.html b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-after-adding-iframe.html
index 5ab2820551080..0289c455f1b74 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-after-adding-iframe.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-after-adding-iframe.html
@@ -4,13 +4,13 @@
 <body>
 <script>
 async_test(t => {
-  let start_length = history.length;
+  let start_length = navigation.entries().length;
 
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   window.onload = () => t.step_timeout(() => {
     navigation.navigate("#top");
-    assert_equals(navigation.entries().length, 2);
+    assert_equals(navigation.entries().length, start_length + 1);
 
     let i = document.createElement("iframe");
     i.src = "/common/blank.html";
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-multiple-steps.html b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-multiple-steps.html
index 059eb214a8b85..24cf0281845f6 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-multiple-steps.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-multiple-steps.html
@@ -3,23 +3,25 @@
 <script src="/resources/testharnessreport.js"></script>
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
-  assert_equals(navigation.entries().length, 1);
+  assert_equals(navigation.entries().length, start_length);
   let key0 = navigation.currentEntry.key;
   await navigation.navigate("#1").committed;
   await navigation.navigate("#2").committed;
   let key2 = navigation.currentEntry.key;
-  assert_equals(navigation.entries().length, 3);
+  assert_equals(navigation.entries().length, start_length + 2);
 
   await navigation.traverseTo(key0).committed;
-  assert_equals(navigation.entries().length, 3);
-  assert_equals(navigation.currentEntry, navigation.entries()[0]);
+  assert_equals(navigation.entries().length, start_length + 2);
+  assert_equals(navigation.currentEntry, navigation.entries()[start_index]);
   assert_equals(key0, navigation.currentEntry.key);
   await navigation.traverseTo(key2).committed;
-  assert_equals(navigation.entries().length, 3);
-  assert_equals(navigation.currentEntry, navigation.entries()[2]);
+  assert_equals(navigation.entries().length, start_length + 2);
+  assert_equals(navigation.currentEntry, navigation.entries()[start_index+2]);
   assert_equals(key2, navigation.currentEntry.key);
 }, "goto() can precisely traverse multiple steps in the joint session history");
 </script>
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-navigates-multiple-iframes.html b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-navigates-multiple-iframes.html
index 3d6adb53413e3..1892ae065e2e3 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-navigates-multiple-iframes.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-navigates-multiple-iframes.html
@@ -6,6 +6,7 @@
 <iframe id="i2" src="resources/slow-no-store.py"></iframe>
 <script>
 promise_test(async t => {
+  let start_length = navigation.entries().length;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   await new Promise(resolve => window.onload = () => t.step_timeout(resolve, 0));
@@ -14,7 +15,7 @@
   await new Promise(resolve => i1.onload = resolve);
   i2.src = "/common/blank.html?navigated";
   await new Promise(resolve => i2.onload = resolve);
-  assert_equals(navigation.entries().length, 1);
+  assert_equals(navigation.entries().length, start_length);
   assert_equals(i1.contentWindow.navigation.entries().length, 2);
   assert_equals(i2.contentWindow.navigation.entries().length, 2);
   assert_equals(i1.contentWindow.navigation.currentEntry.index, 1);
diff --git a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-same-document.html b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-same-document.html
index 1a32bce99c98e..3bd7f4d3d2bf8 100644
--- a/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-same-document.html
+++ b/testing/web-platform/tests/navigation-api/navigation-methods/traverseTo-same-document.html
@@ -3,10 +3,12 @@
 <script src="/resources/testharnessreport.js"></script>
 <script>
 async_test(t => {
+  let start_length = navigation.entries().length;
+  let start_index = navigation.currentEntry.index;
   // Wait for after the load event so that the navigation doesn't get converted
   // into a replace navigation.
   window.onload = () => t.step_timeout(() => {
-    assert_equals(navigation.entries().length, 1);
+    assert_equals(navigation.entries().length, start_length);
 
     let onnavigate_count = 0;
     navigation.onnavigate = () => onnavigate_count++;
@@ -14,27 +16,27 @@
     let key = navigation.currentEntry.key;
     navigation.navigate("#").committed
       .then(t.step_func(() => {
-        assert_equals(navigation.entries().length, 2);
-        assert_equals(navigation.currentEntry, navigation.entries()[1]);
+        assert_equals(navigation.entries().length, start_length + 1);
+        assert_equals(navigation.currentEntry, navigation.entries()[start_index + 1]);
         assert_not_equals(key, navigation.currentEntry.key);
         return navigation.traverseTo(key).committed;
       }))
       .then(t.step_func(() => {
-        assert_equals(navigation.entries().length, 2);
-        assert_equals(navigation.currentEntry, navigation.entries()[0]);
+        assert_equals(navigation.entries().length, start_length + 1);
+        assert_equals(navigation.currentEntry, navigation.entries()[start_index]);
         assert_equals(key, navigation.currentEntry.key);
         assert_true(navigation.canGoForward);
         return navigation.forward().committed;
       }))
       .then(t.step_func(() => {
-        assert_equals(navigation.entries().length, 2);
-        assert_equals(navigation.currentEntry, navigation.entries()[1]);
+        assert_equals(navigation.entries().length, start_length + 1);
+        assert_equals(navigation.currentEntry, navigation.entries()[start_index + 1]);
         assert_true(navigation.canGoBack);
         return navigation.back().committed;
       }))
       .then(t.step_func_done(() => {
-        assert_equals(navigation.entries().length, 2);
-        assert_equals(navigation.currentEntry, navigation.entries()[0]);
+        assert_equals(navigation.entries().length, start_length + 1);
+        assert_equals(navigation.currentEntry, navigation.entries()[start_index]);
         assert_equals(key, navigation.currentEntry.key);
         assert_equals(onnavigate_count, 4);
       }));