diff --git a/src/vs/platform/configuration/test/common/configurationModels.test.ts b/src/vs/platform/configuration/test/common/configurationModels.test.ts
index ef1f5a33328..97b4a40cc91 100644
--- a/src/vs/platform/configuration/test/common/configurationModels.test.ts
+++ b/src/vs/platform/configuration/test/common/configurationModels.test.ts
@@ -37,7 +37,12 @@ suite('ConfigurationModel', () => {
 
 		testObject.setValue('b.c', 1);
 
-		assert.deepEqual(testObject.contents, { 'a': { 'b': 1 }, 'b': { 'c': 1 }, 'f': 1 });
+		const expected: any = {};
+		expected['a'] = { 'b': 1 };
+		expected['f'] = 1;
+		expected['b'] = Object.create(null);
+		expected['b']['c'] = 1;
+		assert.deepStrictEqual(testObject.contents, expected);
 		assert.deepStrictEqual(testObject.keys, ['a.b', 'f', 'b.c']);
 	});
 
@@ -315,17 +320,17 @@ suite('CustomConfigurationModel', () => {
 		const testObject = new ConfigurationModelParser('test');
 		testObject.parseContent('');
 
-		assert.deepEqual(testObject.configurationModel.contents, {});
+		assert.deepStrictEqual(testObject.configurationModel.contents, Object.create(null));
 		assert.deepStrictEqual(testObject.configurationModel.keys, []);
 
 		testObject.parseContent(null!);
 
-		assert.deepEqual(testObject.configurationModel.contents, {});
+		assert.deepStrictEqual(testObject.configurationModel.contents, Object.create(null));
 		assert.deepStrictEqual(testObject.configurationModel.keys, []);
 
 		testObject.parseContent(undefined!);
 
-		assert.deepEqual(testObject.configurationModel.contents, {});
+		assert.deepStrictEqual(testObject.configurationModel.contents, Object.create(null));
 		assert.deepStrictEqual(testObject.configurationModel.keys, []);
 	});
 
diff --git a/src/vs/workbench/services/configuration/test/common/configurationModels.test.ts b/src/vs/workbench/services/configuration/test/common/configurationModels.test.ts
index 653b2a3eb7b..74fecfd1931 100644
--- a/src/vs/workbench/services/configuration/test/common/configurationModels.test.ts
+++ b/src/vs/workbench/services/configuration/test/common/configurationModels.test.ts
@@ -53,7 +53,11 @@ suite('FolderSettingsModelParser', () => {
 
 		testObject.parseContent(JSON.stringify({ 'FolderSettingsModelParser.window': 'window', 'FolderSettingsModelParser.resource': 'resource', 'FolderSettingsModelParser.application': 'application', 'FolderSettingsModelParser.machine': 'executable' }));
 
-		assert.deepEqual(testObject.configurationModel.contents, { 'FolderSettingsModelParser': { 'window': 'window', 'resource': 'resource' } });
+		const expected = Object.create(null);
+		expected['FolderSettingsModelParser'] = Object.create(null);
+		expected['FolderSettingsModelParser']['window'] = 'window';
+		expected['FolderSettingsModelParser']['resource'] = 'resource';
+		assert.deepStrictEqual(testObject.configurationModel.contents, expected);
 	});
 
 	test('parse resource folder settings', () => {
@@ -61,7 +65,10 @@ suite('FolderSettingsModelParser', () => {
 
 		testObject.parseContent(JSON.stringify({ 'FolderSettingsModelParser.window': 'window', 'FolderSettingsModelParser.resource': 'resource', 'FolderSettingsModelParser.application': 'application', 'FolderSettingsModelParser.machine': 'executable' }));
 
-		assert.deepEqual(testObject.configurationModel.contents, { 'FolderSettingsModelParser': { 'resource': 'resource' } });
+		const expected = Object.create(null);
+		expected['FolderSettingsModelParser'] = Object.create(null);
+		expected['FolderSettingsModelParser']['resource'] = 'resource';
+		assert.deepStrictEqual(testObject.configurationModel.contents, expected);
 	});
 
 	test('parse resource and resource language settings', () => {
@@ -69,7 +76,11 @@ suite('FolderSettingsModelParser', () => {
 
 		testObject.parseContent(JSON.stringify({ '[json]': { 'FolderSettingsModelParser.window': 'window', 'FolderSettingsModelParser.resource': 'resource', 'FolderSettingsModelParser.resourceLanguage': 'resourceLanguage', 'FolderSettingsModelParser.application': 'application', 'FolderSettingsModelParser.machine': 'executable' } }));
 
-		assert.deepEqual(testObject.configurationModel.overrides, [{ 'contents': { 'FolderSettingsModelParser': { 'resource': 'resource', 'resourceLanguage': 'resourceLanguage' } }, 'identifiers': ['json'], 'keys': ['FolderSettingsModelParser.resource', 'FolderSettingsModelParser.resourceLanguage'] }]);
+		const expected = Object.create(null);
+		expected['FolderSettingsModelParser'] = Object.create(null);
+		expected['FolderSettingsModelParser']['resource'] = 'resource';
+		expected['FolderSettingsModelParser']['resourceLanguage'] = 'resourceLanguage';
+		assert.deepStrictEqual(testObject.configurationModel.overrides, [{ 'contents': expected, 'identifiers': ['json'], 'keys': ['FolderSettingsModelParser.resource', 'FolderSettingsModelParser.resourceLanguage'] }]);
 	});
 
 	test('reprocess folder settings excludes application and machine setting', () => {
@@ -77,7 +88,11 @@ suite('FolderSettingsModelParser', () => {
 
 		testObject.parseContent(JSON.stringify({ 'FolderSettingsModelParser.resource': 'resource', 'FolderSettingsModelParser.anotherApplicationSetting': 'executable' }));
 
-		assert.deepEqual(testObject.configurationModel.contents, { 'FolderSettingsModelParser': { 'resource': 'resource', 'anotherApplicationSetting': 'executable' } });
+		let expected = Object.create(null);
+		expected['FolderSettingsModelParser'] = Object.create(null);
+		expected['FolderSettingsModelParser']['resource'] = 'resource';
+		expected['FolderSettingsModelParser']['anotherApplicationSetting'] = 'executable';
+		assert.deepStrictEqual(testObject.configurationModel.contents, expected);
 
 		const configurationRegistry = Registry.as<IConfigurationRegistry>(ConfigurationExtensions.Configuration);
 		configurationRegistry.registerConfiguration({
@@ -98,7 +113,11 @@ suite('FolderSettingsModelParser', () => {
 		});
 
 		testObject.parse();
-		assert.deepEqual(testObject.configurationModel.contents, { 'FolderSettingsModelParser': { 'resource': 'resource' } });
+
+		expected = Object.create(null);
+		expected['FolderSettingsModelParser'] = Object.create(null);
+		expected['FolderSettingsModelParser']['resource'] = 'resource';
+		assert.deepStrictEqual(testObject.configurationModel.contents, expected);
 	});
 
 });
@@ -110,7 +129,11 @@ suite('StandaloneConfigurationModelParser', () => {
 
 		testObject.parseContent(JSON.stringify({ 'version': '1.1.1', 'tasks': [] }));
 
-		assert.deepEqual(testObject.configurationModel.contents, { 'tasks': { 'version': '1.1.1', 'tasks': [] } });
+		const expected = Object.create(null);
+		expected['tasks'] = Object.create(null);
+		expected['tasks']['version'] = '1.1.1';
+		expected['tasks']['tasks'] = [];
+		assert.deepStrictEqual(testObject.configurationModel.contents, expected);
 	});
 
 });
diff --git a/src/vs/workbench/test/browser/codeeditor.test.ts b/src/vs/workbench/test/browser/codeeditor.test.ts
index d84c3e0d788..35100e22784 100644
--- a/src/vs/workbench/test/browser/codeeditor.test.ts
+++ b/src/vs/workbench/test/browser/codeeditor.test.ts
@@ -55,52 +55,52 @@ suite('Editor - Range decorations', () => {
 	});
 
 	test('highlight range for the resource if it is an active editor', function () {
-		let range: IRange = { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 };
+		const range: IRange = new Range(1, 1, 1, 1);
 		testObject.highlightRange({ resource: model.uri, range });
 
-		let actuals = rangeHighlightDecorations(model);
+		const actuals = rangeHighlightDecorations(model);
 
-		assert.deepEqual([range], actuals);
+		assert.deepStrictEqual(actuals, [range]);
 	});
 
 	test('remove highlight range', function () {
 		testObject.highlightRange({ resource: model.uri, range: { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 } });
 		testObject.removeHighlightRange();
 
-		let actuals = rangeHighlightDecorations(model);
+		const actuals = rangeHighlightDecorations(model);
 
-		assert.deepStrictEqual([], actuals);
+		assert.deepStrictEqual(actuals, []);
 	});
 
 	test('highlight range for the resource removes previous highlight', function () {
 		testObject.highlightRange({ resource: model.uri, range: { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 } });
-		let range: IRange = { startLineNumber: 2, startColumn: 2, endLineNumber: 4, endColumn: 3 };
+		const range: IRange = new Range(2, 2, 4, 3);
 		testObject.highlightRange({ resource: model.uri, range });
 
-		let actuals = rangeHighlightDecorations(model);
+		const actuals = rangeHighlightDecorations(model);
 
-		assert.deepEqual([range], actuals);
+		assert.deepStrictEqual(actuals, [range]);
 	});
 
 	test('highlight range for a new resource removes highlight of previous resource', function () {
 		testObject.highlightRange({ resource: model.uri, range: { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 } });
 
-		let anotherModel = prepareActiveEditor('anotherModel');
-		let range: IRange = { startLineNumber: 2, startColumn: 2, endLineNumber: 4, endColumn: 3 };
+		const anotherModel = prepareActiveEditor('anotherModel');
+		const range: IRange = new Range(2, 2, 4, 3);
 		testObject.highlightRange({ resource: anotherModel.uri, range });
 
 		let actuals = rangeHighlightDecorations(model);
-		assert.deepStrictEqual([], actuals);
+		assert.deepStrictEqual(actuals, []);
 		actuals = rangeHighlightDecorations(anotherModel);
-		assert.deepEqual([range], actuals);
+		assert.deepStrictEqual(actuals, [range]);
 	});
 
 	test('highlight is removed on model change', function () {
 		testObject.highlightRange({ resource: model.uri, range: { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 } });
 		prepareActiveEditor('anotherModel');
 
-		let actuals = rangeHighlightDecorations(model);
-		assert.deepStrictEqual([], actuals);
+		const actuals = rangeHighlightDecorations(model);
+		assert.deepStrictEqual(actuals, []);
 	});
 
 	test('highlight is removed on cursor position change', function () {
@@ -109,27 +109,27 @@ suite('Editor - Range decorations', () => {
 			position: new Position(2, 1)
 		});
 
-		let actuals = rangeHighlightDecorations(model);
-		assert.deepStrictEqual([], actuals);
+		const actuals = rangeHighlightDecorations(model);
+		assert.deepStrictEqual(actuals, []);
 	});
 
 	test('range is not highlight if not active editor', function () {
-		let model = aModel(URI.file('some model'));
+		const model = aModel(URI.file('some model'));
 		testObject.highlightRange({ resource: model.uri, range: { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 } });
 
-		let actuals = rangeHighlightDecorations(model);
-		assert.deepStrictEqual([], actuals);
+		const actuals = rangeHighlightDecorations(model);
+		assert.deepStrictEqual(actuals, []);
 	});
 
 	test('previous highlight is not removed if not active editor', function () {
-		let range: IRange = { startLineNumber: 1, startColumn: 1, endLineNumber: 1, endColumn: 1 };
+		const range = new Range(1, 1, 1, 1);
 		testObject.highlightRange({ resource: model.uri, range });
 
-		let model1 = aModel(URI.file('some model'));
+		const model1 = aModel(URI.file('some model'));
 		testObject.highlightRange({ resource: model1.uri, range: { startLineNumber: 2, startColumn: 1, endLineNumber: 2, endColumn: 1 } });
 
-		let actuals = rangeHighlightDecorations(model);
-		assert.deepEqual([range], actuals);
+		const actuals = rangeHighlightDecorations(model);
+		assert.deepStrictEqual(actuals, [range]);
 	});
 
 	function prepareActiveEditor(resource: string): TextModel {