fix

Author: Lightning00Blade

src/McpResponse.ts

@@ -912,8 +912,7 @@ Call ${handleDialog.name} to handle it before continuing.`);
       }
       const aggregates = this.#heapSnapshotOptions.aggregates;
       if (aggregates) {
-        const entries = Object.entries(aggregates);
-        const sortedEntries = entries.sort((a, b) => b[1].self - a[1].self);
+        const sortedEntries = HeapSnapshotFormatter.sort(aggregates);
 
         const paginationData = this.#dataWithPagination(
           sortedEntries,

src/formatters/HeapSnapshotFormatter.ts

@@ -53,4 +53,15 @@ export class HeapSnapshotFormatter {
       retainedSize: info.maxRet,
     }));
   }
+
+  static sort(
+    aggregates: Record<
+      string,
+      DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo
+    >,
+  ): Array<
+    [string, DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo]
+  > {
+    return Object.entries(aggregates).sort((a, b) => b[1].self - a[1].self);
+  }
 }

tests/formatters/HeapSnapshotFormatter.test.ts

@@ -0,0 +1,92 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import assert from 'node:assert';
+import {describe, it} from 'node:test';
+
+import {HeapSnapshotFormatter} from '../../src/formatters/HeapSnapshotFormatter.js';
+import type {DevTools} from '../../src/third_party/index.js';
+
+describe('HeapSnapshotFormatter', () => {
+  const mockAggregates: Record<
+    string,
+    DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo
+  > = {
+    ObjectA: {
+      name: 'ObjectA',
+      count: 10,
+      self: 100,
+      maxRet: 1000,
+      distance: 1,
+      idxs: [],
+    } as unknown as DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo,
+    ObjectB: {
+      name: 'ObjectB',
+      count: 5,
+      self: 50,
+      maxRet: 500,
+      distance: 2,
+      idxs: [],
+    } as unknown as DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo,
+  };
+
+  describe('toString', () => {
+    it('formats data as CSV and sorts by self size', () => {
+      const formatter = new HeapSnapshotFormatter(mockAggregates);
+      const result = formatter.toString();
+      const expected = [
+        'className,count,selfSize,maxRetainedSize',
+        '"ObjectA",10,100,1000',
+        '"ObjectB",5,50,500',
+      ].join('\n');
+      assert.strictEqual(result, expected);
+    });
+  });
+
+  describe('toJSON', () => {
+    it('returns structured data sorted by self size', () => {
+      const formatter = new HeapSnapshotFormatter(mockAggregates);
+      const result = formatter.toJSON();
+      assert.deepStrictEqual(result, [
+        {
+          className: 'ObjectA',
+          count: 10,
+          selfSize: 100,
+          retainedSize: 1000,
+        },
+        {
+          className: 'ObjectB',
+          count: 5,
+          selfSize: 50,
+          retainedSize: 500,
+        },
+      ]);
+    });
+  });
+
+  describe('sort', () => {
+    it('sorts aggregates by self size descending', () => {
+      const unsortedAggregates: Record<
+        string,
+        DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo
+      > = {
+        ObjectB: {
+          name: 'ObjectB',
+          self: 50,
+        } as unknown as DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo,
+        ObjectA: {
+          name: 'ObjectA',
+          self: 100,
+        } as unknown as DevTools.HeapSnapshotModel.HeapSnapshotModel.AggregatedInfo,
+      };
+
+      const result = HeapSnapshotFormatter.sort(unsortedAggregates);
+      assert.strictEqual(result.length, 2);
+      assert.strictEqual(result[0][0], 'ObjectA');
+      assert.strictEqual(result[1][0], 'ObjectB');
+    });
+  });
+});