Move waitForUpdate to test-utils

test/test-utils.js

@@ -302,3 +302,23 @@ export function wrapInMatrixClientContext(WrappedComponent) {
     }
     return Wrapper;
 }
+
+/**
+ * Call fn before calling componentDidUpdate on a react component instance, inst.
+ * @param {React.Component} inst an instance of a React component.
+ * @returns {Promise} promise that resolves when componentDidUpdate is called on
+ *                    given component instance.
+ */
+export function waitForUpdate(inst) {
+    return new Promise((resolve, reject) => {
+        const cdu = inst.componentDidUpdate;
+
+        inst.componentDidUpdate = (prevProps, prevState, snapshot) => {
+            resolve();
+
+            if (cdu) cdu(prevProps, prevState, snapshot);
+
+            inst.componentDidUpdate = cdu;
+        };
+    });
+}