diff --git a/packages/core/src/browser/storage-service.spec.ts b/packages/core/src/browser/storage-service.spec.ts
index 0d9d2d741f4b3..496abf60e7892 100644
--- a/packages/core/src/browser/storage-service.spec.ts
+++ b/packages/core/src/browser/storage-service.spec.ts
@@ -6,7 +6,7 @@
  */
 
 import { LocalStorageService, StorageService } from './storage-service';
-import * as assert from 'assert';
+import { expect } from 'chai';
 import { TestLogger } from '../common/test/test-logger';
 
 let storageService: StorageService;
@@ -21,24 +21,24 @@ describe("storage-service", () => {
         storageService.setData('foo', {
             test: 'foo'
         });
-        assert(await storageService.getData('bar', 'bar') === 'bar');
-        assert((await storageService.getData('foo', {
+        expect(await storageService.getData('bar', 'bar')).equals('bar');
+        expect((await storageService.getData('foo', {
             test: 'bar'
-        })).test === 'foo');
+        })).test).equals('foo');
     });
 
     it("removes data", async () => {
         storageService.setData('foo', {
             test: 'foo'
         });
-        assert((await storageService.getData('foo', {
+        expect((await storageService.getData('foo', {
             test: 'bar'
-        })).test === 'foo');
+        })).test).equals('foo');
 
         storageService.setData('foo', undefined);
-        assert((await storageService.getData('foo', {
+        expect((await storageService.getData('foo', {
             test: 'bar'
-        })).test === 'bar');
+        })).test).equals('bar');
     });
 
 });
diff --git a/packages/core/src/browser/storage-service.ts b/packages/core/src/browser/storage-service.ts
index c71ad830d52b0..194537fb34da7 100644
--- a/packages/core/src/browser/storage-service.ts
+++ b/packages/core/src/browser/storage-service.ts
@@ -24,6 +24,7 @@ export interface StorageService {
      * returns the data stored for the given key or the provided default value if nothing is stored for the given key.
      */
     getData<T>(key: string, defaultValue: T): Promise<T>;
+    getData<T>(key: string): Promise<T | undefined>;
 }
 
 interface LocalStorage {
@@ -50,10 +51,10 @@ export class LocalStorageService implements StorageService {
         } else {
             delete this.storage[this.prefix(key)];
         }
-        return Promise.resolve(undefined);
+        return Promise.resolve();
     }
 
-    getData<T>(key: string, defaultValue: T): Promise<T> {
+    getData<T>(key: string, defaultValue?: T): Promise<T | undefined> {
         const result = this.storage[this.prefix(key)];
         if (result === undefined) {
             return Promise.resolve(defaultValue);
diff --git a/packages/core/src/browser/widget-manager.spec.ts b/packages/core/src/browser/widget-manager.spec.ts
index 48b53163109ce..1e133c2416241 100644
--- a/packages/core/src/browser/widget-manager.spec.ts
+++ b/packages/core/src/browser/widget-manager.spec.ts
@@ -6,7 +6,7 @@
  */
 
 
-import * as assert from 'assert';
+import { expect } from 'chai';
 import { TestLogger } from '../common/test/test-logger';
 import { WidgetManager, WidgetFactory } from './widget-manager';
 import { Widget } from '@phosphor/widgets';
@@ -51,9 +51,8 @@ describe("widget-manager", () => {
     it("creates and caches widgets", async () => {
         const wA = await widgetManager.getOrCreateWidget('test', 'widgetA');
         const wB = await widgetManager.getOrCreateWidget('test', 'widgetB');
-        assert.notStrictEqual(wA, wB);
-        assert.strictEqual(wA, await widgetManager.getOrCreateWidget('test', 'widgetA'));
+        expect(wA).not.equals(wB);
+        expect(wA).equals(await widgetManager.getOrCreateWidget('test', 'widgetA'));
     });
 
 });
-
diff --git a/packages/workspace/src/browser/workspace-storage-service.ts b/packages/workspace/src/browser/workspace-storage-service.ts
index 6b3ae15d45715..1dca10f34a075 100644
--- a/packages/workspace/src/browser/workspace-storage-service.ts
+++ b/packages/workspace/src/browser/workspace-storage-service.ts
@@ -34,17 +34,17 @@ export class WorkspaceStorageService implements StorageService {
         if (!this.root) {
             await this.rootPromise;
         }
-        const fullKey = this.getKey(key);
+        const fullKey = this.prefixWorkspaceURI(key);
         return this.storageService.setData(fullKey, data);
     }
 
-    async getData<T>(key: string, defaultValue: T): Promise<T> {
+    async getData<T>(key: string, defaultValue?: T): Promise<T | undefined> {
         await this.rootPromise;
-        const fullKey = this.getKey(key);
+        const fullKey = this.prefixWorkspaceURI(key);
         return this.storageService.getData(fullKey, defaultValue);
     }
 
-    protected getKey(originalKey: string): string {
+    protected prefixWorkspaceURI(originalKey: string): string {
         return this.root.uri + ":" + originalKey;
     }
 }