1 files changed, 35 insertions, 0 deletions
diff --git a/devtools/shared/heapsnapshot/tests/xpcshell/test_census_diff_05.js b/devtools/shared/heapsnapshot/tests/xpcshell/test_census_diff_05.js
new file mode 100644
index 0000000000..1ce0cfeb5b
--- /dev/null
+++ b/devtools/shared/heapsnapshot/tests/xpcshell/test_census_diff_05.js
@@ -0,0 +1,35 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test diffing census reports of breakdown by "allocationStack".
+
+const BREAKDOWN = {
+  by: "allocationStack",
+  then: { by: "count", count: true, bytes: true },
+  noStack: { by: "count", count: true, bytes: true },
+};
+
+const stack1 = saveStack();
+const stack2 = saveStack();
+const stack3 = saveStack();
+
+const REPORT1 = new Map([
+  [stack1, { count: 10, bytes: 100 }],
+  [stack2, { count: 1, bytes: 10 }],
+]);
+
+const REPORT2 = new Map([
+  [stack2, { count: 10, bytes: 100 }],
+  [stack3, { count: 1, bytes: 10 }],
+]);
+
+const EXPECTED = new Map([
+  [stack1, { count: -10, bytes: -100 }],
+  [stack2, { count: 9, bytes: 90 }],
+  [stack3, { count: 1, bytes: 10 }],
+]);
+
+function run_test() {
+  assertDiff(BREAKDOWN, REPORT1, REPORT2, EXPECTED);
+}