diff --git a/extensions/notebook/src/test/book/bookTocManager.test.ts b/extensions/notebook/src/test/book/bookTocManager.test.ts
index 433e54a08a..1526f8413e 100644
--- a/extensions/notebook/src/test/book/bookTocManager.test.ts
+++ b/extensions/notebook/src/test/book/bookTocManager.test.ts
@@ -90,15 +90,18 @@ describe('BookTocManagerTests', function () {
 			let bookTocManager: BookTocManager = new BookTocManager();
 			let expectedSection: IJupyterBookSectionV2[] = [{
 				title: 'notebook2',
-				file: path.join(subfolder, 'notebook2')
+				file: path.posix.join(subfolder, 'notebook2')
 			},
 			{
 				title: 'notebook3',
-				file: path.join(subfolder, 'notebook3')
+				file: path.posix.join(subfolder, 'notebook3')
 			}];
 			await bookTocManager.createBook(bookFolderPath, root2FolderPath);
-			should(equalTOC(bookTocManager.tableofContents[1].sections, expectedSection)).be.true;
-			should((bookTocManager.tableofContents[1] as IJupyterBookSectionV2).file).be.equal(path.join(path.sep, subfolder, 'index'));
+			const index = bookTocManager.tableofContents.findIndex(entry => entry.file === path.posix.join(path.posix.sep, subfolder, 'index'));
+			should(index).not.be.equal(-1, 'Should find a section with the Subfolder entry');
+			if (index !== -1) {
+				should(equalTOC(bookTocManager.tableofContents[index].sections, expectedSection)).be.true;
+			}
 		});
 
 		it('should ignore invalid file extensions', async () => {
@@ -130,88 +133,88 @@ describe('BookTocManagerTests', function () {
 				version: BookVersion.v1,
 				sourceBook: {
 					'rootBookFolderPath': sourceBookFolderPath,
-					'bookContentFolderPath': path.join(sourceBookFolderPath, 'content'),
-					'tocPath': path.join(sourceBookFolderPath, '_data', 'toc.yml'),
-					'readme': path.join(sourceBookFolderPath, 'content', 'readme.md'),
+					'bookContentFolderPath': path.posix.join(sourceBookFolderPath, 'content'),
+					'tocPath': path.posix.join(sourceBookFolderPath, '_data', 'toc.yml'),
+					'readme': path.posix.join(sourceBookFolderPath, 'content', 'readme.md'),
 					'toc': [
 						{
 							'title': 'Notebook 1',
-							'file': path.join(path.sep, 'sectionA', 'notebook1')
+							'file': path.posix.join(path.posix.sep, 'sectionA', 'notebook1')
 						},
 						{
 							'title': 'Notebook 2',
-							'file': path.join(path.sep, 'sectionA', 'notebook2')
+							'file': path.posix.join(path.posix.sep, 'sectionA', 'notebook2')
 						}
 					]
 				},
 				sectionA: {
-					'contentPath': path.join(sourceBookFolderPath, 'content', 'sectionA', 'readme.md'),
-					'sectionRoot': path.join(sourceBookFolderPath, 'content', 'sectionA'),
+					'contentPath': path.posix.join(sourceBookFolderPath, 'content', 'sectionA', 'readme.md'),
+					'sectionRoot': path.posix.join(sourceBookFolderPath, 'content', 'sectionA'),
 					'sectionName': 'Section A',
-					'notebook1': path.join(sourceBookFolderPath, 'content', 'sectionA', 'notebook1.ipynb'),
-					'notebook2': path.join(sourceBookFolderPath, 'content', 'sectionA', 'notebook2.ipynb'),
+					'notebook1': path.posix.join(sourceBookFolderPath, 'content', 'sectionA', 'notebook1.ipynb'),
+					'notebook2': path.posix.join(sourceBookFolderPath, 'content', 'sectionA', 'notebook2.ipynb'),
 					'sectionFormat': [
 						{
 							'title': 'Notebook 1',
-							'file': path.join(path.sep, 'sectionA', 'notebook1')
+							'file': path.posix.join(path.posix.sep, 'sectionA', 'notebook1')
 						},
 						{
 							'title': 'Notebook 2',
-							'file': path.join(path.sep, 'sectionA', 'notebook2')
+							'file': path.posix.join(path.posix.sep, 'sectionA', 'notebook2')
 						}
 					]
 				},
 				sectionB: {
-					'contentPath': path.join(sourceBookFolderPath, 'content', 'sectionB', 'readme.md'),
-					'sectionRoot': path.join(sourceBookFolderPath, 'content', 'sectionB'),
+					'contentPath': path.posix.join(sourceBookFolderPath, 'content', 'sectionB', 'readme.md'),
+					'sectionRoot': path.posix.join(sourceBookFolderPath, 'content', 'sectionB'),
 					'sectionName': 'Section B',
-					'notebook3': path.join(sourceBookFolderPath, 'content', 'sectionB', 'notebook3.ipynb'),
-					'notebook4': path.join(sourceBookFolderPath, 'content', 'sectionB', 'notebook4.ipynb'),
+					'notebook3': path.posix.join(sourceBookFolderPath, 'content', 'sectionB', 'notebook3.ipynb'),
+					'notebook4': path.posix.join(sourceBookFolderPath, 'content', 'sectionB', 'notebook4.ipynb'),
 					'sectionFormat': [
 						{
 							'title': 'Notebook 3',
-							'file': path.join(path.sep, 'sectionB', 'notebook3')
+							'file': path.posix.join(path.posix.sep, 'sectionB', 'notebook3')
 						},
 						{
 							'title': 'Notebook 4',
-							'file': path.join(path.sep, 'sectionB', 'notebook4')
+							'file': path.posix.join(path.posix.sep, 'sectionB', 'notebook4')
 						}
 					]
 				},
 				notebook5: {
-					'contentPath': path.join(sourceBookFolderPath, 'content', 'notebook5.ipynb')
+					'contentPath': path.posix.join(sourceBookFolderPath, 'content', 'notebook5.ipynb')
 				},
 				targetBook: {
 					'rootBookFolderPath': targetBookFolderPath,
-					'bookContentFolderPath': path.join(targetBookFolderPath, 'content'),
-					'tocPath': path.join(targetBookFolderPath, '_data', 'toc.yml'),
-					'readme': path.join(targetBookFolderPath, 'content', 'readme.md'),
+					'bookContentFolderPath': path.posix.join(targetBookFolderPath, 'content'),
+					'tocPath': path.posix.join(targetBookFolderPath, '_data', 'toc.yml'),
+					'readme': path.posix.join(targetBookFolderPath, 'content', 'readme.md'),
 					'toc': [
 						{
 							'title': 'Welcome page',
-							'file': path.join(path.sep, 'readme'),
+							'file': path.posix.join(path.posix.sep, 'readme'),
 						},
 						{
 							'title': 'Section C',
-							'file': path.join(path.sep, 'sectionC', 'readme'),
+							'file': path.posix.join(path.posix.sep, 'sectionC', 'readme'),
 							'sections': [
 								{
 									'title': 'Notebook 6',
-									'file': path.join(path.sep, 'sectionC', 'notebook6')
+									'file': path.posix.join(path.posix.sep, 'sectionC', 'notebook6')
 								}
 							]
 						}
 					]
 				},
 				sectionC: {
-					'contentPath': path.join(targetBookFolderPath, 'content', 'sectionC', 'readme.md'),
-					'sectionRoot': path.join(targetBookFolderPath, 'content', 'sectionC'),
+					'contentPath': path.posix.join(targetBookFolderPath, 'content', 'sectionC', 'readme.md'),
+					'sectionRoot': path.posix.join(targetBookFolderPath, 'content', 'sectionC'),
 					'sectionName': 'Section C',
-					'notebook6': path.join(targetBookFolderPath, 'content', 'sectionC', 'notebook6.ipynb'),
+					'notebook6': path.posix.join(targetBookFolderPath, 'content', 'sectionC', 'notebook6.ipynb'),
 					'sectionFormat': [
 						{
 							'title': 'Notebook 6',
-							'file': path.join(path.sep, 'sectionC', 'notebook6')
+							'file': path.posix.join(path.posix.sep, 'sectionC', 'notebook6')
 						}
 					]
 				}
@@ -221,77 +224,77 @@ describe('BookTocManagerTests', function () {
 				sourceBook: {
 					'rootBookFolderPath': sourceBookFolderPath,
 					'bookContentFolderPath': sourceBookFolderPath,
-					'tocPath': path.join(sourceBookFolderPath, '_toc.yml'),
-					'readme': path.join(sourceBookFolderPath, 'readme.md')
+					'tocPath': path.posix.join(sourceBookFolderPath, '_toc.yml'),
+					'readme': path.posix.join(sourceBookFolderPath, 'readme.md')
 				},
 				sectionA: {
-					'contentPath': path.join(sourceBookFolderPath, 'sectionA', 'readme.md'),
-					'sectionRoot': path.join(sourceBookFolderPath, 'sectionA'),
+					'contentPath': path.posix.join(sourceBookFolderPath, 'sectionA', 'readme.md'),
+					'sectionRoot': path.posix.join(sourceBookFolderPath, 'sectionA'),
 					'sectionName': 'Section A',
-					'notebook1': path.join(sourceBookFolderPath, 'sectionA', 'notebook1.ipynb'),
-					'notebook2': path.join(sourceBookFolderPath, 'sectionA', 'notebook2.ipynb'),
+					'notebook1': path.posix.join(sourceBookFolderPath, 'sectionA', 'notebook1.ipynb'),
+					'notebook2': path.posix.join(sourceBookFolderPath, 'sectionA', 'notebook2.ipynb'),
 					'sectionFormat': [
 						{
 							'title': 'Notebook 1',
-							'file': path.join(path.sep, 'sectionA', 'notebook1')
+							'file': path.posix.join(path.posix.sep, 'sectionA', 'notebook1')
 						},
 						{
 							'title': 'Notebook 2',
-							'file': path.join(path.sep, 'sectionA', 'notebook2')
+							'file': path.posix.join(path.posix.sep, 'sectionA', 'notebook2')
 						}
 					]
 				},
 				sectionB: {
-					'contentPath': path.join(sourceBookFolderPath, 'sectionB', 'readme.md'),
-					'sectionRoot': path.join(sourceBookFolderPath, 'sectionB'),
+					'contentPath': path.posix.join(sourceBookFolderPath, 'sectionB', 'readme.md'),
+					'sectionRoot': path.posix.join(sourceBookFolderPath, 'sectionB'),
 					'sectionName': 'Section B',
-					'notebook3': path.join(sourceBookFolderPath, 'sectionB', 'notebook3.ipynb'),
-					'notebook4': path.join(sourceBookFolderPath, 'sectionB', 'notebook4.ipynb'),
+					'notebook3': path.posix.join(sourceBookFolderPath, 'sectionB', 'notebook3.ipynb'),
+					'notebook4': path.posix.join(sourceBookFolderPath, 'sectionB', 'notebook4.ipynb'),
 					'sectionFormat': [
 						{
 							'title': 'Notebook 3',
-							'file': path.join(path.sep, 'sectionB', 'notebook3')
+							'file': path.posix.join(path.posix.sep, 'sectionB', 'notebook3')
 						},
 						{
 							'title': 'Notebook 4',
-							'file': path.join(path.sep, 'sectionB', 'notebook4')
+							'file': path.posix.join(path.posix.sep, 'sectionB', 'notebook4')
 						}
 					]
 				},
 				notebook5: {
-					'contentPath': path.join(sourceBookFolderPath, 'notebook5.ipynb')
+					'contentPath': path.posix.join(sourceBookFolderPath, 'notebook5.ipynb')
 				},
 				targetBook: {
 					'rootBookFolderPath': targetBookFolderPath,
 					'bookContentFolderPath': targetBookFolderPath,
-					'tocPath': path.join(targetBookFolderPath, '_toc.yml'),
-					'readme': path.join(targetBookFolderPath, 'readme.md'),
+					'tocPath': path.posix.join(targetBookFolderPath, '_toc.yml'),
+					'readme': path.posix.join(targetBookFolderPath, 'readme.md'),
 					'toc': [
 						{
 							'title': 'Welcome',
-							'file': path.join(path.sep, 'readme'),
+							'file': path.posix.join(path.posix.sep, 'readme'),
 						},
 						{
 							'title': 'Section C',
-							'file': path.join(path.sep, 'sectionC', 'readme'),
+							'file': path.posix.join(path.posix.sep, 'sectionC', 'readme'),
 							'sections': [
 								{
 									'title': 'Notebook 6',
-									'file': path.join(path.sep, 'sectionC', 'notebook6')
+									'file': path.posix.join(path.posix.sep, 'sectionC', 'notebook6')
 								}
 							]
 						}
 					]
 				},
 				sectionC: {
-					'contentPath': path.join(targetBookFolderPath, 'sectionC', 'readme.md'),
-					'sectionRoot': path.join(targetBookFolderPath, 'sectionC'),
+					'contentPath': path.posix.join(targetBookFolderPath, 'sectionC', 'readme.md'),
+					'sectionRoot': path.posix.join(targetBookFolderPath, 'sectionC'),
 					'sectionName': 'Section C',
-					'notebook6': path.join(targetBookFolderPath, 'sectionC', 'notebook6.ipynb'),
+					'notebook6': path.posix.join(targetBookFolderPath, 'sectionC', 'notebook6.ipynb'),
 					'sectionFormat': [
 						{
 							'title': 'Notebook 6',
-							'file': path.join(path.sep, 'sectionC', 'notebook6')
+							'file': path.posix.join(path.posix.sep, 'sectionC', 'notebook6')
 						}
 					]
 				}
@@ -343,7 +346,7 @@ describe('BookTocManagerTests', function () {
 						version: run.version,
 						page: {
 							title: run.sectionA.sectionName,
-							file: path.join(path.sep, 'sectionA', 'readme'),
+							file: path.posix.join(path.posix.sep, 'sectionA', 'readme'),
 							sections: run.sectionA.sectionFormat
 						}
 					};
@@ -362,7 +365,7 @@ describe('BookTocManagerTests', function () {
 						version: run.version,
 						page: {
 							title: run.sectionB.sectionName,
-							file: path.join(path.sep, 'sectionB', 'readme'),
+							file: path.posix.join(path.posix.sep, 'sectionB', 'readme'),
 							sections: run.sectionB.sectionFormat
 						}
 					};
@@ -376,7 +379,7 @@ describe('BookTocManagerTests', function () {
 							sections: [
 								{
 									'title': 'Notebook 5',
-									'file': path.join(path.sep, 'notebook5')
+									'file': path.posix.join(path.posix.sep, 'notebook5')
 								}
 							]
 						},
@@ -386,19 +389,19 @@ describe('BookTocManagerTests', function () {
 						version: run.version,
 						page: {
 							'title': 'Notebook 5',
-							'file': path.join(path.sep, 'notebook5')
+							'file': path.posix.join(path.posix.sep, 'notebook5')
 						}
 					};
 
 					let duplicatedNbTreeItemFormat: BookTreeItemFormat = {
 						title: 'Duplicated Notebook',
-						contentPath: path.join(duplicatedNotebookPath, 'notebook5.ipynb'),
+						contentPath: path.posix.join(duplicatedNotebookPath, 'notebook5.ipynb'),
 						root: duplicatedNotebookPath,
 						tableOfContents: {
 							sections: [
 								{
 									'title': 'Notebook 5',
-									'file': path.join(path.sep, 'notebook5')
+									'file': path.posix.join(path.posix.sep, 'notebook5')
 								}
 							]
 						},
@@ -408,7 +411,7 @@ describe('BookTocManagerTests', function () {
 						version: run.version,
 						page: {
 							'title': 'Notebook 5',
-							'file': path.join(path.sep, 'notebook5')
+							'file': path.posix.join(path.posix.sep, 'notebook5')
 						}
 					};
 
@@ -420,9 +423,9 @@ describe('BookTocManagerTests', function () {
 					duplicatedNotebook = new BookTreeItem(duplicatedNbTreeItemFormat, undefined);
 
 
-					sectionC.uri = path.join('sectionC', 'readme');
-					sectionA.uri = path.join('sectionA', 'readme');
-					sectionB.uri = path.join('sectionB', 'readme');
+					sectionC.uri = path.posix.join('sectionC', 'readme');
+					sectionA.uri = path.posix.join('sectionA', 'readme');
+					sectionB.uri = path.posix.join('sectionB', 'readme');
 
 					targetBook.contextValue = 'savedBook';
 					sectionA.contextValue = 'section';
@@ -443,7 +446,7 @@ describe('BookTocManagerTests', function () {
 					notebook.sections = [
 						{
 							'title': 'Notebook 5',
-							'file': path.join(path.sep, 'notebook5')
+							'file': path.posix.join(path.posix.sep, 'notebook5')
 						}
 					];
 					duplicatedNotebook.sections = notebook.sections;
@@ -498,7 +501,7 @@ describe('BookTocManagerTests', function () {
 					bookTocManager = new BookTocManager(targetBookModel, sourceBookModel);
 					await bookTocManager.updateBook(sectionB, sectionC, {
 						'title': 'Notebook 6',
-						'file': path.join(path.sep, 'sectionC', 'notebook6')
+						'file': path.posix.join(path.posix.sep, 'sectionC', 'notebook6')
 					});
 					const sectionCFiles = await fs.promises.readdir(path.join(run.targetBook.bookContentFolderPath, 'sectionC'));
 					const sectionBFiles = await fs.promises.readdir(path.join(run.targetBook.bookContentFolderPath, 'sectionB'));
@@ -516,7 +519,7 @@ describe('BookTocManagerTests', function () {
 				it('Remove notebook from book', async () => {
 					let toc: JupyterBookSection[] = yaml.safeLoad((await fs.promises.readFile(notebook.tableOfContentsPath)).toString());
 					let notebookInToc = toc.some(section => {
-						if (section.title === 'Notebook 5' && section.file === path.join(path.sep, 'notebook5')) {
+						if (section.title === 'Notebook 5' && section.file === path.posix.join(path.posix.sep, 'notebook5')) {
 							return true;
 						}
 						return false;
@@ -529,7 +532,7 @@ describe('BookTocManagerTests', function () {
 					const listFiles = await fs.promises.readdir(run.sourceBook.bookContentFolderPath);
 					toc = yaml.safeLoad((await fs.promises.readFile(notebook.tableOfContentsPath)).toString());
 					notebookInToc = toc.some(section => {
-						if (section.title === 'Notebook 5' && section.file === path.join(path.sep, 'notebook5')) {
+						if (section.title === 'Notebook 5' && section.file === path.posix.join(path.posix.sep, 'notebook5')) {
 							return true;
 						}
 						return false;