Hoisted assert clipboard into TestAppContext

crates/gpui/src/app.rs

@@ -627,6 +627,14 @@ impl TestAppContext {
             }
         })
     }
+
+    pub fn assert_clipboard_content(&mut self, expected_content: Option<&str>) {
+        self.update(|cx| {
+            let actual_content = cx.read_from_clipboard().map(|item| item.text().to_owned());
+            let expected_content = expected_content.map(|content| content.to_owned());
+            assert_eq!(actual_content, expected_content);
+        })
+    }
 }
 
 impl AsyncAppContext {