test(Popup): try fixing list/tree sizing flakiness

packages/jui/integration-tests/modal-window-and-tree.cy.tsx

@@ -31,6 +31,7 @@ describe("ModalWindow containing Tree", () => {
         />
       </ModalWindow>
     );
+    cy.findByRole("dialog").invoke("width").should("be.greaterThan", 180);
     matchImageSnapshot("ModalWindow-sized-based-on-Tree");
   });
 });

packages/jui/src/Popup/Popup.cy.tsx

@@ -4,22 +4,32 @@ import { composeStories } from "@storybook/react";
 import * as stories from "./Popup.stories";
 import { Popup } from "./Popup";
 
-const { Default, DefaultPosition, DefaultSize, MenuContent, ListContent } =
-  composeStories(stories);
+const {
+  Default,
+  DefaultPosition,
+  DefaultSize,
+  MenuContent,
+  ListContent,
+  TreeContent,
+} = composeStories(stories);
 
 describe("Popup", () => {
   describe("sizing and positioning", () => {
-    it("Sets the size based on content, and places the popup centered, if no bounds provided", () => {
+    it.only("Sets the size based on content, and places the popup centered, if no bounds provided", () => {
       cy.mount(<Default />);
       matchImageSnapshot("Popup-default-bounds--simple");
       cy.mount(<MenuContent />);
       matchImageSnapshot("Popup-default-bounds--menu");
+
+      // List and Tree use virtualization, and are not immediately sized in the first render
       cy.mount(<ListContent />);
+      cy.findByRole("dialog").invoke("width").should("be.greaterThan", 100);
+
       matchImageSnapshot("Popup-default-bounds--list");
+      cy.mount(<TreeContent />);
+      cy.findByRole("dialog").invoke("width").should("be.greaterThan", 150);
 
-      // Tree uses virtualization, and sizing is flaky at the moment. FIXME
-      // cy.mount(<TreeContent />);
-      // matchImageSnapshot("Popup-default-bounds--tree");
+      matchImageSnapshot("Popup-default-bounds--tree");
     });
 
     it("takes default position into account, while setting size based on content", () => {

packages/jui/src/Tree/Tree.cy.tsx

@@ -12,6 +12,7 @@ describe("Tree", () => {
     cy.mount(<Static />);
 
     cy.contains("Foo").click().type("{enter}");
+    cy.findByRole("treeitem", { name: "FooBar" });
     matchImageSnapshot("Tree-nested-single-child-expansion");
   });