diff --git a/testing/web-platform/meta/fs/FileSystemDirectoryHandle-removeEntry.https.any.js.ini b/testing/web-platform/meta/fs/FileSystemDirectoryHandle-removeEntry.https.any.js.ini
index 9c413c62150b..5b68c2a5902d 100644
--- a/testing/web-platform/meta/fs/FileSystemDirectoryHandle-removeEntry.https.any.js.ini
+++ b/testing/web-platform/meta/fs/FileSystemDirectoryHandle-removeEntry.https.any.js.ini
@@ -26,7 +26,7 @@
   [removeEntry() with a path separator should fail.]
     expected: FAIL
 
-  [removeEntry() while the file has an open writable succeeds]
+  [removeEntry() while the file has an open writable fails]
     expected: FAIL
 
 
@@ -58,5 +58,5 @@
   [removeEntry() with a path separator should fail.]
     expected: FAIL
 
-  [removeEntry() while the file has an open writable succeeds]
+  [removeEntry() while the file has an open writable fails]
     expected: FAIL
diff --git a/testing/web-platform/tests/fs/resources/messaging-serialize-helpers.js b/testing/web-platform/tests/fs/resources/messaging-serialize-helpers.js
index 063fe4173d98..13c900c0cbcf 100644
--- a/testing/web-platform/tests/fs/resources/messaging-serialize-helpers.js
+++ b/testing/web-platform/tests/fs/resources/messaging-serialize-helpers.js
@@ -30,12 +30,17 @@ async function serialize_handle(handle) {
 // serialized properties shared by both FileSystemFileHandle and
 // FileSystemDirectoryHandle.
 async function serialize_file_system_handle(handle) {
-  const read_permission =
-    await handle.queryPermission({ mode: 'read' });
-
-  const write_permission =
-    await handle.queryPermission({ mode: 'readwrite' })
+  let read_permission = "granted";
+  let write_permission = "granted";
+  // query-permission is part of the File System Acecss API
+  // https://wicg.github.io/file-system-access, which may not be supported
+  if ("queryPermission" in FileSystemHandle.prototype) {
+    read_permission =
+      await handle.queryPermission({ mode: 'read' });
 
+    write_permission =
+      await handle.queryPermission({ mode: 'readwrite' })
+  }
   return {
     kind: handle.kind,
     name: handle.name,
diff --git a/testing/web-platform/tests/fs/resources/test-helpers.js b/testing/web-platform/tests/fs/resources/test-helpers.js
index 91834e0677a3..e27666a1beb7 100644
--- a/testing/web-platform/tests/fs/resources/test-helpers.js
+++ b/testing/web-platform/tests/fs/resources/test-helpers.js
@@ -86,3 +86,21 @@ function garbageCollect() {
   if (self.gc)
     self.gc();
 };
+
+async function cleanup(test, value, cleanup_func) {
+  test.add_cleanup(async () => {
+    try {
+      await cleanup_func();
+    } catch (e) {
+      // Ignore any errors when removing files, as tests might already remove
+      // the file.
+    }
+  });
+  return value;
+}
+
+async function cleanup_writable(test, value) {
+  return cleanup(test, value, async () => {
+    value.close();
+  });
+}
diff --git a/testing/web-platform/tests/fs/script-tests/FileSystemBaseHandle-IndexedDB.js b/testing/web-platform/tests/fs/script-tests/FileSystemBaseHandle-IndexedDB.js
index 855e52f04ddf..15a0c2a3b579 100644
--- a/testing/web-platform/tests/fs/script-tests/FileSystemBaseHandle-IndexedDB.js
+++ b/testing/web-platform/tests/fs/script-tests/FileSystemBaseHandle-IndexedDB.js
@@ -6,7 +6,6 @@ directory_test(async (t, root_dir) => {
     const db = await createDatabase(t, db => {
       const store = db.createObjectStore('store');
     });
-    t.add_cleanup(() => deleteAllDatabases(t));
 
     const value = handles;
 
@@ -28,7 +27,6 @@ directory_test(async (t, root_dir) => {
     const db = await createDatabase(t, db => {
       const store = db.createObjectStore('store');
     });
-    t.add_cleanup(() => deleteAllDatabases(t));
 
     const value = handles;
 
@@ -53,7 +51,6 @@ directory_test(async (t, root_dir) => {
     const db = await createDatabase(t, db => {
       const store = db.createObjectStore('store');
     });
-    t.add_cleanup(() => deleteAllDatabases(t));
 
     const value = {handles, blob: new Blob(["foobar"])};
 
@@ -80,7 +77,6 @@ directory_test(async (t, root_dir) => {
     const db = await createDatabase(t, db => {
       const store = db.createObjectStore('store');
     });
-    t.add_cleanup(() => deleteAllDatabases(t));
 
     const value = handles;
 
@@ -107,7 +103,6 @@ directory_test(async (t, root_dir) => {
     const db = await createDatabase(t, db => {
       const store = db.createObjectStore('store', {keyPath: 'key'});
     });
-    t.add_cleanup(() => deleteAllDatabases(t));
 
     const value = handles;
     let tx = db.transaction('store', 'readwrite');
diff --git a/testing/web-platform/tests/fs/script-tests/FileSystemDirectoryHandle-removeEntry.js b/testing/web-platform/tests/fs/script-tests/FileSystemDirectoryHandle-removeEntry.js
index 01e2ebe10889..c28e46ca2e14 100644
--- a/testing/web-platform/tests/fs/script-tests/FileSystemDirectoryHandle-removeEntry.js
+++ b/testing/web-platform/tests/fs/script-tests/FileSystemDirectoryHandle-removeEntry.js
@@ -23,7 +23,6 @@ directory_test(async (t, root) => {
   await root.removeEntry('dir-to-remove');
 
   assert_array_equals(await getSortedDirectoryEntries(root), ['file-to-keep']);
-  await promise_rejects_dom(t, 'NotFoundError', getSortedDirectoryEntries(dir));
 }, 'removeEntry() to remove an empty directory');
 
 directory_test(async (t, root) => {
@@ -93,11 +92,13 @@ directory_test(async (t, root) => {
   await createFileWithContents(t, 'file-to-keep', 'abc', root);
 
   const writable = await handle.createWritable();
-  await root.removeEntry('file-to-remove');
-  await promise_rejects_dom(t, 'NotFoundError', getFileContents(handle));
+  await promise_rejects_dom(
+    t, 'InvalidModificationError', root.removeEntry('file-to-remove'));
 
   await writable.close();
+  await root.removeEntry('file-to-remove');
+
   assert_array_equals(
       await getSortedDirectoryEntries(root),
-      ['file-to-keep', 'file-to-remove']);
-}, 'removeEntry() while the file has an open writable succeeds');
+      ['file-to-keep']);
+}, 'removeEntry() while the file has an open writable fails');
diff --git a/testing/web-platform/tests/fs/script-tests/FileSystemFileHandle-move.js b/testing/web-platform/tests/fs/script-tests/FileSystemFileHandle-move.js
index 5b2d25faf345..4057b0f8d46a 100644
--- a/testing/web-platform/tests/fs/script-tests/FileSystemFileHandle-move.js
+++ b/testing/web-platform/tests/fs/script-tests/FileSystemFileHandle-move.js
@@ -74,7 +74,7 @@ directory_test(async (t, root) => {
   const handle = await createFileWithContents(t, 'file-before', 'abc', root);
 
   // Cannot rename handle with an active writable.
-  const stream = await handle.createWritable();
+  const stream = await cleanup_writable(t, await handle.createWritable());
   await promise_rejects_dom(
       t, 'NoModificationAllowedError', handle.move('file-after'));
 
@@ -90,7 +90,7 @@ directory_test(async (t, root) => {
       await createFileWithContents(t, 'file-after', '123', root);
 
   // Cannot overwrite a handle with an active writable.
-  const stream = await handle_dest.createWritable();
+  const stream = await cleanup_writable(t, await handle_dest.createWritable());
   await promise_rejects_dom(
       t, 'NoModificationAllowedError', handle.move('file-after'));
 
@@ -259,7 +259,7 @@ directory_test(async (t, root) => {
   const file = await createFileWithContents(t, 'file', 'abc', dir_src);
 
   // Cannot move handle with an active writable.
-  const stream = await file.createWritable();
+  const stream = await cleanup_writable(t, await file.createWritable());
   await promise_rejects_dom(t, 'NoModificationAllowedError', file.move(dir_dest));
 
   assert_array_equals(
@@ -282,7 +282,7 @@ directory_test(async (t, root) => {
   const file = await createFileWithContents(t, 'file-before', 'abc', dir_src);
 
   // Cannot move handle with an active writable.
-  const stream = await file.createWritable();
+  const stream = await cleanup_writable(t, await file.createWritable());
   await promise_rejects_dom(t, 'NoModificationAllowedError', file.move(dir_dest));
 
   assert_array_equals(
@@ -307,7 +307,7 @@ directory_test(async (t, root) => {
   const file_dest = await createFileWithContents(t, 'file', '123', dir_dest);
 
   // Cannot overwrite handle with an active writable.
-  const stream = await file_dest.createWritable();
+  const stream = await cleanup_writable(t, await file_dest.createWritable());
   await promise_rejects_dom(t, 'NoModificationAllowedError', file.move(dir_dest));
 
   assert_array_equals(
@@ -334,7 +334,7 @@ directory_test(async (t, root) => {
       await createFileWithContents(t, 'file-dest', '123', dir_dest);
 
   // Cannot overwrite handle with an active writable.
-  const stream = await file_dest.createWritable();
+  const stream = await cleanup_writable(t, await file_dest.createWritable());
   await promise_rejects_dom(
       t, 'NoModificationAllowedError', file.move(dir_dest, 'file-dest'));