1 files changed, 88 insertions, 0 deletions
diff --git a/devtools/client/shared/test/xpcshell/test_undoStack.js b/devtools/client/shared/test/xpcshell/test_undoStack.js
new file mode 100644
index 0000000000..dafb007120
--- /dev/null
+++ b/devtools/client/shared/test/xpcshell/test_undoStack.js
@@ -0,0 +1,88 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const { UndoStack } = require("resource://devtools/client/shared/undo.js");
+
+const MAX_SIZE = 5;
+
+function run_test() {
+  let str = "";
+  const stack = new UndoStack(MAX_SIZE);
+
+  function add(ch) {
+    stack.do(
+      function () {
+        str += ch;
+      },
+      function () {
+        str = str.slice(0, -1);
+      }
+    );
+  }
+
+  Assert.ok(!stack.canUndo());
+  Assert.ok(!stack.canRedo());
+
+  // Check adding up to the limit of the size
+  add("a");
+  Assert.ok(stack.canUndo());
+  Assert.ok(!stack.canRedo());
+
+  add("b");
+  add("c");
+  add("d");
+  add("e");
+
+  Assert.equal(str, "abcde");
+
+  // Check a simple undo+redo
+  stack.undo();
+
+  Assert.equal(str, "abcd");
+  Assert.ok(stack.canRedo());
+
+  stack.redo();
+  Assert.equal(str, "abcde");
+  Assert.ok(!stack.canRedo());
+
+  // Check an undo followed by a new action
+  stack.undo();
+  Assert.equal(str, "abcd");
+
+  add("q");
+  Assert.equal(str, "abcdq");
+  Assert.ok(!stack.canRedo());
+
+  stack.undo();
+  Assert.equal(str, "abcd");
+  stack.redo();
+  Assert.equal(str, "abcdq");
+
+  // Revert back to the beginning of the queue...
+  while (stack.canUndo()) {
+    stack.undo();
+  }
+  Assert.equal(str, "");
+
+  // Now put it all back....
+  while (stack.canRedo()) {
+    stack.redo();
+  }
+  Assert.equal(str, "abcdq");
+
+  // Now go over the undo limit...
+  add("1");
+  add("2");
+  add("3");
+
+  Assert.equal(str, "abcdq123");
+
+  // And now undoing the whole stack should only undo 5 actions.
+  while (stack.canUndo()) {
+    stack.undo();
+  }
+
+  Assert.equal(str, "abc");
+}