Migration/delete database confirmation in react (#542)

Co-authored-by: Steve Faulkner <471400+southpolesteve@users.noreply.github.com>
Co-authored-by: Steve Faulkner <stfaul@microsoft.com>

src/Explorer/Explorer.test.tsx

@@ -0,0 +1,43 @@
+jest.mock("./../Common/dataAccess/deleteDatabase");
+jest.mock("./../Shared/Telemetry/TelemetryProcessor");
+import * as ko from "knockout";
+import { deleteDatabase } from "./../Common/dataAccess/deleteDatabase";
+import * as ViewModels from "./../Contracts/ViewModels";
+import Explorer from "./Explorer";
+
+describe("Explorer.isLastDatabase() and Explorer.isLastNonEmptyDatabase()", () => {
+  let explorer: Explorer;
+  beforeAll(() => {
+    (deleteDatabase as jest.Mock).mockResolvedValue(undefined);
+  });
+
+  beforeEach(() => {
+    explorer = new Explorer();
+  });
+
+  it("should be true if only 1 database", () => {
+    const database = {} as ViewModels.Database;
+    explorer.databases = ko.observableArray<ViewModels.Database>([database]);
+    expect(explorer.isLastDatabase()).toBe(true);
+  });
+
+  it("should be false if only 2 databases", () => {
+    const database = {} as ViewModels.Database;
+    const database2 = {} as ViewModels.Database;
+    explorer.databases = ko.observableArray<ViewModels.Database>([database, database2]);
+    expect(explorer.isLastDatabase()).toBe(false);
+  });
+
+  it("should be false if not last empty database", () => {
+    const database = {} as ViewModels.Database;
+    explorer.databases = ko.observableArray<ViewModels.Database>([database]);
+    expect(explorer.isLastNonEmptyDatabase()).toBe(false);
+  });
+
+  it("should be true if last non empty database", () => {
+    const database = {} as ViewModels.Database;
+    database.collections = ko.observableArray<ViewModels.Collection>([{} as ViewModels.Collection]);
+    explorer.databases = ko.observableArray<ViewModels.Database>([database]);
+    expect(explorer.isLastNonEmptyDatabase()).toBe(true);
+  });
+});