1 files changed, 34 insertions, 0 deletions
diff --git a/dom/heapsnapshot/tests/unit/test_census_diff_05.js b/dom/heapsnapshot/tests/unit/test_census_diff_05.js
new file mode 100644
index 000000000..b6d99f823
--- /dev/null
+++ b/dom/heapsnapshot/tests/unit/test_census_diff_05.js
@@ -0,0 +1,34 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// 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);
+}