Add Simple Account Picker for use with Always Encrypted (#9707)

Adds the ability for the user to select from two or more linked azure accounts, using an integrated UI dialog, when executing a query that requires a Always Encrypted column master key located in Azure Key Vault.

extensions/mssql/src/test/util/dataCache.test.ts

@@ -0,0 +1,70 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the Source EULA. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { DataItemCache } from '../../util/dataCache';
+import 'mocha';
+import { should } from 'chai'; should();
+import * as TypeMoq from "typemoq";
+
+describe('DataItemCache', function (): void {
+
+	const testCacheItem = 'Test Cache Item';
+	const fetchFunction = () => Promise.resolve(testCacheItem);
+	let fetchFunctionMock: TypeMoq.IMock<() => Promise<string>>;
+	let dataItemCache: DataItemCache<String>;
+
+	beforeEach(function (): void {
+		fetchFunctionMock = TypeMoq.Mock.ofInstance(fetchFunction);
+		fetchFunctionMock.setup(fx => fx()).returns(() => Promise.resolve(testCacheItem));
+		dataItemCache = new DataItemCache<string>(fetchFunctionMock.object, 1);
+	});
+
+	it('Should be initialized empty', function (): void {
+		dataItemCache.should.have.property('cachedItem').and.be.undefined;
+	});
+
+	it('Should be initialized as expired', function (): void {
+		dataItemCache.isCacheExpired().should.be.true;
+	});
+
+	it('Should not be expired immediately after first data fetch', async function (): Promise<void> {
+		await dataItemCache.getData();
+
+		dataItemCache.isCacheExpired().should.be.false;
+	});
+
+	it('Should return expected cached item from getValue()', async function (): Promise<void> {
+		let actualValue = await dataItemCache.getData();
+
+		actualValue.should.equal(testCacheItem);
+	});
+
+	it('Should be expired after data is fetched and TTL passes', async function (): Promise<void> {
+		await dataItemCache.getData();
+		await sleep(1.1);
+
+		dataItemCache.isCacheExpired().should.be.true;
+	});
+
+	it('Should call fetch function once for consecutive getValue() calls prior to expiration', async function (): Promise<void> {
+		await dataItemCache.getData();
+		await dataItemCache.getData();
+		await dataItemCache.getData();
+
+		fetchFunctionMock.verify(fx => fx() ,TypeMoq.Times.once());
+	});
+
+	it('Should call fetch function twice for consecutive getValue() calls if TTL expires in between', async function (): Promise<void> {
+		await dataItemCache.getData();
+		await sleep(1.1);
+		await dataItemCache.getData();
+
+		fetchFunctionMock.verify(fx => fx(), TypeMoq.Times.exactly(2));
+	});
+});
+
+const sleep = (seconds: number) => {
+	return new Promise(resolve => setTimeout(resolve, 1000 * seconds));
+}