Mock subscribe template (home-assistant#7529)

Author: balloob

demo/src/stubs/template.ts

@@ -6,4 +6,11 @@ export const mockTemplate = (hass: MockHomeAssistant) => {
       body: { message: "Template dev tool does not work in the demo." },
     })
   );
+  hass.mockWS("render_template", (msg, onChange) => {
+    onChange!({
+      result: msg.template,
+      listeners: { all: false, domains: [], entities: [], time: false },
+    });
+    return () => {};
+  });
 };

gallery/src/demos/demo-hui-markdown-card.ts

@@ -1,6 +1,8 @@
 import { html } from "@polymer/polymer/lib/utils/html-tag";
 /* eslint-plugin-disable lit */
 import { PolymerElement } from "@polymer/polymer/polymer-element";
+import { mockTemplate } from "../../../demo/src/stubs/template";
+import { provideHass } from "../../../src/fake_data/provide_hass";
 import "../components/demo-cards";
 
 const CONFIGS = [
@@ -254,7 +256,7 @@ const CONFIGS = [
 
 class DemoMarkdown extends PolymerElement {
   static get template() {
-    return html` <demo-cards configs="[[_configs]]"></demo-cards> `;
+    return html` <demo-cards id="demos" configs="[[_configs]]"></demo-cards> `;
   }
 
   static get properties() {
@@ -265,6 +267,12 @@ class DemoMarkdown extends PolymerElement {
       },
     };
   }
+
+  public ready() {
+    super.ready();
+    const hass = provideHass(this.$.demos);
+    mockTemplate(hass);
+  }
 }
 
 customElements.define("demo-hui-markdown-card", DemoMarkdown);