Removing the code with less precision and uncommenting the code with …

src/router/sorClass.ts

@@ -537,12 +537,8 @@ function iterateSwapAmountsApproximation(
     // 1.042818e-12 while using normal js math operations it was
     // 1.0428184989387553e-12. This loss of precision caused an important bug
 
-    // let weighted_average_SPaS = sumSPaSDividedByDerivativeSPaSs.div(
-    //     sumInverseDerivativeSPaSs
-    // );
-    const weighted_average_SPaS = bnum(
-        sumSPaSDividedByDerivativeSPaSs.toNumber() /
-            sumInverseDerivativeSPaSs.toNumber()
+    const weighted_average_SPaS = sumSPaSDividedByDerivativeSPaSs.div(
+        sumInverseDerivativeSPaSs
     );
 
     swapAmounts.forEach((swapAmount, i) => {

test/fullSwaps.spec.ts

@@ -139,7 +139,7 @@ describe('Tests full swaps against known values', () => {
         // These test should highlight any changes in maths that may unexpectedly change result
         assert.equal(
             swapInfo.returnAmount.toString(),
-            '2932409883691685',
+            '2932409883691175',
             'V2 sanity check.'
         );
     }).timeout(10000);
@@ -184,7 +184,7 @@ describe('Tests full swaps against known values', () => {
             swapInfo.tokenAddresses[swapInfo.swaps[0].assetOutIndex],
             USDC.address
         );
-        assert.equal(swapInfo.swaps[0].amount, '89883768143240164');
+        assert.equal(swapInfo.swaps[0].amount, '89883768143225903');
         assert.equal(
             swapInfo.swaps[1].poolId,
             '0x57755f7dec33320bca83159c26e93751bfd30fbe'
@@ -197,7 +197,7 @@ describe('Tests full swaps against known values', () => {
             swapInfo.tokenAddresses[swapInfo.swaps[1].assetOutIndex],
             USDC.address
         );
-        assert.equal(swapInfo.swaps[1].amount, '10116231856759836');
+        assert.equal(swapInfo.swaps[1].amount, '10116231856774097');
     }).timeout(10000);
 
     it('should full swap weighted swapExactOut', async () => {
@@ -234,7 +234,7 @@ describe('Tests full swaps against known values', () => {
         });
 
         // The expected test results are from previous version
-        assert.equal(swapInfo.returnAmount.toString(), '99251606996075153');
+        assert.equal(swapInfo.returnAmount.toString(), '99251606996078174');
         assert.equal(swapInfo.swaps.length, 2);
         assert.equal(
             swapInfo.swaps[0].poolId,
@@ -426,7 +426,7 @@ describe('Tests full swaps against known values', () => {
             swapInfo.tokenAddresses[swapInfo.swaps[0].assetOutIndex],
             USDC.address
         );
-        assert.equal(swapInfo.swaps[0].amount, '692256505473389013');
+        assert.equal(swapInfo.swaps[0].amount, '692256505473351912');
         assert.equal(
             swapInfo.swaps[1].poolId,
             '0x57755f7dec33320bca83159c26e93751bfd30fbe'
@@ -439,7 +439,7 @@ describe('Tests full swaps against known values', () => {
             swapInfo.tokenAddresses[swapInfo.swaps[1].assetOutIndex],
             USDC.address
         );
-        assert.equal(swapInfo.swaps[1].amount, '77743494526610987');
+        assert.equal(swapInfo.swaps[1].amount, '77743494526648088');
     }).timeout(10000);
 
     it('should full swap stable & weighted swapExactOut', async () => {
@@ -480,7 +480,7 @@ describe('Tests full swaps against known values', () => {
             },
         });
 
-        assert.equal(swapInfo.returnAmount.toString(), '100600365514359821527');
+        assert.equal(swapInfo.returnAmount.toString(), '100600365514359819807');
         assert.equal(swapInfo.swaps.length, 3);
         assert.equal(
             swapInfo.swaps[0].poolId,

test/precisionTest.spec.ts

@@ -0,0 +1,54 @@
+// TS_NODE_PROJECT='tsconfig.testing.json' npx mocha -r ts-node/register test/fullSwaps.spec.ts
+import { BigNumber, parseFixed } from '@ethersproject/bignumber';
+import { Zero } from '@ethersproject/constants';
+import { JsonRpcProvider } from '@ethersproject/providers';
+import cloneDeep from 'lodash.clonedeep';
+import { assert } from 'chai';
+import { SubgraphPoolBase, SwapTypes } from '../src/types';
+import { getFullSwap } from './lib/testHelpers';
+import precisionTestPools from './testData/precisionTestPools.json';
+import _ from 'lodash';
+
+const B80BAL20WETH = '0x5c6ee304399dbdb9c8ef030ab642b10820db8f56';
+const USDC = '0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48';
+
+const provider = new JsonRpcProvider(``);
+
+describe('Tests full swaps against known values', () => {
+    const gasPrice = parseFixed('30', 9);
+
+    it('Should have a reasonable return amount value', async () => {
+        const tokenIn = B80BAL20WETH;
+        const tokenOut = USDC;
+        const swapType = SwapTypes.SwapExactIn;
+        const returnAmountDecimals = 18;
+        const maxPools = 4;
+        const swapAmount = parseFixed('14', 18);
+        const swapGas = BigNumber.from('100000');
+        const costOutputToken = Zero;
+
+        const swapInfo = await getFullSwap(
+            cloneDeep(
+                precisionTestPools.map((obj) =>
+                    _.omitBy(obj, _.isNull)
+                ) as SubgraphPoolBase[]
+            ),
+            tokenIn,
+            tokenOut,
+            returnAmountDecimals,
+            maxPools,
+            swapType,
+            swapAmount,
+            costOutputToken,
+            gasPrice,
+            provider,
+            swapGas
+        );
+
+        assert.equal(
+            swapInfo.returnAmount.toString(),
+            '243265259',
+            'Should have a reasonable return amount value'
+        );
+    }).timeout(10000);
+});