solana.js: added loadHistory test

javascript/solana.js/src/accounts/aggregatorHistoryBuffer.ts

@@ -56,7 +56,7 @@ export class AggregatorHistoryBuffer extends Account<
   }
 
   /**
-   * Decode an aggregators history buffer and return an array of historical samples
+   * Decode an aggregators history buffer and return an array of historical samples in ascending order by timestamp.
    * @params historyBuffer the historyBuffer AccountInfo stored on-chain
    * @return the array of {@linkcode types.AggregatorHistoryRow} samples
    */
@@ -74,13 +74,15 @@ export class AggregatorHistoryBuffer extends Account<
     const front: Array<types.AggregatorHistoryRow> = [];
     const tail: Array<types.AggregatorHistoryRow> = [];
 
-    for (let i = 12; i < historyBuffer.length; i += ROW_SIZE) {
-      if (i + ROW_SIZE > historyBuffer.length) {
+    const buffer = historyBuffer.slice(12);
+
+    for (let i = 0; i < buffer.length; i += ROW_SIZE) {
+      if (i + ROW_SIZE > buffer.length) {
         break;
       }
 
       const row = types.AggregatorHistoryRow.fromDecoded(
-        types.AggregatorHistoryRow.layout().decode(historyBuffer, i)
+        types.AggregatorHistoryRow.layout().decode(buffer, i)
       );
 
       if (row.timestamp.eq(new anchor.BN(0))) {

javascript/solana.js/test/history.spec.ts

@@ -0,0 +1,43 @@
+import 'mocha';
+import assert from 'assert';
+
+import { AggregatorAccount, SwitchboardProgram } from '../src';
+import { clusterApiUrl, Connection } from '@solana/web3.js';
+
+describe('History Tests', () => {
+  let program: SwitchboardProgram;
+
+  before(async () => {
+    program = await SwitchboardProgram.load(
+      'devnet',
+      new Connection(process.env.SOLANA_DEVNET_RPC ?? clusterApiUrl('devnet'))
+    );
+  });
+
+  /** History buffer should be returned with the oldest elements (lowest timestamps) first */
+  it('Verifies a history buffer is decoded in order', async () => {
+    const [aggregatorAccount, aggregator] = await AggregatorAccount.load(
+      program,
+      'GvDMxPzN1sCj7L26YDK2HnMRXEQmQ2aemov8YBtPS7vR'
+    );
+
+    const history = await aggregatorAccount.loadHistory();
+
+    let lastTimestamp: number | undefined = undefined;
+    for (const [n, row] of history.entries()) {
+      if (lastTimestamp === undefined) {
+        lastTimestamp = row.timestamp.toNumber();
+        continue;
+      }
+
+      const currentTimestamp = row.timestamp.toNumber();
+
+      assert(
+        lastTimestamp < currentTimestamp,
+        `Aggregator History is out of order at element ${n}, prev ${lastTimestamp}, curr ${currentTimestamp}`
+      );
+
+      lastTimestamp = currentTimestamp;
+    }
+  });
+});