diff --git a/scripts/taker-mock/src/begin-auction.js b/scripts/taker-mock/src/begin-auction.js
index e0e11ae..d7c4bb3 100644
--- a/scripts/taker-mock/src/begin-auction.js
+++ b/scripts/taker-mock/src/begin-auction.js
@@ -1,16 +1,57 @@
 
+function delay(time) {
+    return new Promise(resolve => setTimeout(resolve, time));
+}
+
+
 async function beginAuction(ob) {
-    const depth = await ob.marketDepth()
+    // BUY
+    let depth = await ob.marketDepth()
     console.log(depth)
-    //for (const ask of depth.asks) {
-    const ask = depth.asks[0]
-    const price = ask[0]
-    const size = ask[1]
-    const amountInBToken = price * size
-    const expectedAmountOut = size
-    const res = await ob.beginAuction("ETH-USD", "BUY", amountInBToken)
-    console.log(res)
-    //}
+    let sumBToken = 0
+    let sumAToken = 0
+    for (const ask of depth.asks) {
+        const price = parseFloat(ask[0])
+        const size = parseFloat(ask[1])
+        sumAToken += size
+        sumBToken += size * price
+
+    }
+    let res = await ob.beginAuction("ETH-USD", "BUY", sumBToken)
+    if (!res) {
+        console.error('beginAuction BUY failed')
+    }
+    else if (parseFloat(res.amountOut) === sumAToken) {
+        console.log('SUCCESS BUY amount-out IS equal to sum of size', res.amountOut, sumAToken)
+    }
+    else {
+        console.error('BUY amount out is NOT equal not to sum of size', res.amountOut, sumAToken)
+        return false;
+    }
+
+    // SELL (reset)
+    depth = await ob.marketDepth()
+    sumAToken = 0
+    sumBToken = 0
+    for (const bid of depth.bids) {
+        const price = parseFloat(bid[0])
+        const size = parseFloat(bid[1])
+        sumAToken += size
+        sumBToken += size * price
+
+    }
+    res = await ob.beginAuction("ETH-USD", "SELL", sumAToken)
+    if (!res) {
+        console.error('beginAuction SELL failed')
+    }
+    else if (parseFloat(res.amountOut) === sumBToken) {
+        console.log('SUCCESS SELL amount-out IS equal to sum of size', res.amountOut, sumBToken)
+        return true;
+    }
+    else {
+        console.error('SELL amount out is NOT equal not to sum of size', res.amountOut, sumBToken)
+        return false;
+    }
 
     return true
 }
diff --git a/scripts/taker-mock/src/order-book.js b/scripts/taker-mock/src/order-book.js
index aa53c30..529279a 100644
--- a/scripts/taker-mock/src/order-book.js
+++ b/scripts/taker-mock/src/order-book.js
@@ -22,6 +22,14 @@ class Orderbook {
             }
             const response = await fetch(url, req);
 
+            // error
+            if (response.status >= 400) {
+                const message = await response.text()
+                console.error(message)
+
+                return null
+            }
+
             // Parse and work with the JSON response
             return await response.json();
         }