zjquery: Add set_height helper.

frontend_tests/node_tests/buddy_list.js

@@ -31,7 +31,7 @@ function init_simulated_scrolling() {
 
     $("#buddy_list_wrapper")[0] = elem;
 
-    $("#buddy_list_wrapper_padding").height = () => 0;
+    $("#buddy_list_wrapper_padding").set_height(0);
 
     return elem;
 }

frontend_tests/node_tests/compose_actions.js

@@ -223,6 +223,8 @@ run_test("start", () => {
         abort_xhr_called = true;
     };
 
+    $("#compose-textarea").set_height(50);
+
     assert_hidden("#compose_controls");
     cancel();
     assert(abort_xhr_called);

frontend_tests/zjsunit/zjquery.js

@@ -152,6 +152,8 @@ exports.make_new_elem = function (selector, opts) {
     let value;
     let css;
     let shown = false;
+    let height;
+
     const find_results = new Map();
     let my_parent;
     const parents_result = new Map();
@@ -234,7 +236,12 @@ exports.make_new_elem = function (selector, opts) {
         hasClass(class_name) {
             return classes.has(class_name);
         },
-        height: noop,
+        height() {
+            if (height === undefined) {
+                throw new Error(`Please call $("${selector}").set_height`);
+            }
+            return height;
+        },
         hide() {
             shown = false;
             return self;
@@ -325,6 +332,9 @@ exports.make_new_elem = function (selector, opts) {
         serializeArray() {
             return self;
         },
+        set_height(fake_height) {
+            height = fake_height;
+        },
         set_parent(parent_elem) {
             my_parent = parent_elem;
         },