1 files changed, 70 insertions, 0 deletions
diff --git a/devtools/client/shared/test/shared-redux-head.js b/devtools/client/shared/test/shared-redux-head.js
new file mode 100644
index 0000000000..b0bbfc8172
--- /dev/null
+++ b/devtools/client/shared/test/shared-redux-head.js
@@ -0,0 +1,70 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+/* eslint no-unused-vars: [2, {"vars": "local"}] */
+/* import-globals-from ./shared-head.js */
+
+// Common utility functions for working with Redux stores.  The file is meant
+// to be safe to load in both mochitest and xpcshell environments.
+
+/**
+ * Wait until the store has reached a state that matches the predicate.
+ * @param Store store
+ *        The Redux store being used.
+ * @param function predicate
+ *        A function that returns true when the store has reached the expected
+ *        state.
+ * @return Promise
+ *         Resolved once the store reaches the expected state.
+ */
+function waitUntilState(store, predicate) {
+  return new Promise(resolve => {
+    const unsubscribe = store.subscribe(check);
+
+    info(`Waiting for state predicate "${predicate}"`);
+    function check() {
+      if (predicate(store.getState())) {
+        info(`Found state predicate "${predicate}"`);
+        unsubscribe();
+        resolve();
+      }
+    }
+
+    // Fire the check immediately in case the action has already occurred
+    check();
+  });
+}
+
+/**
+ * Wait until a particular action has been emitted by the store.
+ * @param {Store} store
+ *        The Redux store being used.
+ * @param {String} actionType
+ *        The expected action to wait for.
+ * @param {Number} count
+ *         Number of times to expect the action to occur. Default is once.
+ * @return Promise
+ *         Resolved once the expected action is emitted by the store.
+ */
+function waitUntilAction(store, actionType, count = 1) {
+  return new Promise(resolve => {
+    const unsubscribe = store.subscribe(check);
+    const history = store.history;
+    let index = history.length;
+
+    info(`Waiting for action "${actionType}"`);
+    function check() {
+      const action = history[index++];
+      if (action && action.type === actionType) {
+        info(`Found action "${actionType}"`);
+        count--;
+        if (count === 0) {
+          unsubscribe();
+          resolve(store.getState());
+        }
+      }
+    }
+  });
+}