1 files changed, 75 insertions, 0 deletions
diff --git a/devtools/shared/heapsnapshot/tests/xpcshell/test_census_diff_01.js b/devtools/shared/heapsnapshot/tests/xpcshell/test_census_diff_01.js
new file mode 100644
index 0000000000..c90b34af70
--- /dev/null
+++ b/devtools/shared/heapsnapshot/tests/xpcshell/test_census_diff_01.js
@@ -0,0 +1,75 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test diffing census reports of breakdown by "internalType".
+
+const BREAKDOWN = {
+  by: "internalType",
+  then: { by: "count", count: true, bytes: true },
+};
+
+const REPORT1 = {
+  JSObject: {
+    count: 10,
+    bytes: 100,
+  },
+  "js::Shape": {
+    count: 50,
+    bytes: 500,
+  },
+  JSString: {
+    count: 0,
+    bytes: 0,
+  },
+  "js::LazyScript": {
+    count: 1,
+    bytes: 10,
+  },
+};
+
+const REPORT2 = {
+  JSObject: {
+    count: 11,
+    bytes: 110,
+  },
+  "js::Shape": {
+    count: 51,
+    bytes: 510,
+  },
+  JSString: {
+    count: 1,
+    bytes: 1,
+  },
+  "js::BaseShape": {
+    count: 1,
+    bytes: 42,
+  },
+};
+
+const EXPECTED = {
+  JSObject: {
+    count: 1,
+    bytes: 10,
+  },
+  "js::Shape": {
+    count: 1,
+    bytes: 10,
+  },
+  JSString: {
+    count: 1,
+    bytes: 1,
+  },
+  "js::LazyScript": {
+    count: -1,
+    bytes: -10,
+  },
+  "js::BaseShape": {
+    count: 1,
+    bytes: 42,
+  },
+};
+
+function run_test() {
+  assertDiff(BREAKDOWN, REPORT1, REPORT2, EXPECTED);
+}