1 files changed, 62 insertions, 0 deletions
diff --git a/devtools/shared/heapsnapshot/tests/xpcshell/test_HeapAnalyses_takeCensusDiff_01.js b/devtools/shared/heapsnapshot/tests/xpcshell/test_HeapAnalyses_takeCensusDiff_01.js
new file mode 100644
index 0000000000..9703229438
--- /dev/null
+++ b/devtools/shared/heapsnapshot/tests/xpcshell/test_HeapAnalyses_takeCensusDiff_01.js
@@ -0,0 +1,62 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+"use strict";
+
+// Test that the HeapAnalyses{Client,Worker} can take diffs between censuses.
+
+const BREAKDOWN = {
+  by: "objectClass",
+  then: { by: "count", count: true, bytes: false },
+  other: { by: "count", count: true, bytes: false },
+};
+
+add_task(async function () {
+  const client = new HeapAnalysesClient();
+
+  const markers = [allocationMarker()];
+
+  const firstSnapshotFilePath = saveNewHeapSnapshot();
+
+  // Allocate and hold an additional AllocationMarker object so we can see it in
+  // the next heap snapshot.
+  markers.push(allocationMarker());
+
+  const secondSnapshotFilePath = saveNewHeapSnapshot();
+
+  await client.readHeapSnapshot(firstSnapshotFilePath);
+  await client.readHeapSnapshot(secondSnapshotFilePath);
+  ok(true, "Should have read both heap snapshot files");
+
+  const { delta } = await client.takeCensusDiff(
+    firstSnapshotFilePath,
+    secondSnapshotFilePath,
+    { breakdown: BREAKDOWN }
+  );
+
+  equal(
+    delta.AllocationMarker.count,
+    1,
+    "There exists one new AllocationMarker in the second heap snapshot"
+  );
+
+  const { delta: deltaTreeNode } = await client.takeCensusDiff(
+    firstSnapshotFilePath,
+    secondSnapshotFilePath,
+    { breakdown: BREAKDOWN },
+    { asTreeNode: true }
+  );
+
+  // Have to manually set these because symbol properties aren't structured
+  // cloned.
+  delta[CensusUtils.basisTotalBytes] = deltaTreeNode.totalBytes;
+  delta[CensusUtils.basisTotalCount] = deltaTreeNode.totalCount;
+
+  compareCensusViewData(
+    BREAKDOWN,
+    delta,
+    deltaTreeNode,
+    "Returning delta-census as a tree node represents same data as the report"
+  );
+
+  client.destroy();
+});