fix(tests): Do not accrue floating point errors in money calculation …

…for business-to-consumer-tax-calculation-gross-without-checkpoints-test (#618)

packages/openactive-integration-tests/test/helpers/flow-stages/flow-stage-recipes.js

@@ -11,6 +11,7 @@ const { FlowStageUtils } = require('./flow-stage-utils');
 const { OrderFeedUpdateFlowStageUtils } = require('./order-feed-update');
 const { PFlowStage } = require('./p');
 const { TestInterfaceActionFlowStage } = require('./test-interface-action');
+const { fixCalculatedMoneyValue } = require('../money-utils');
 
 /**
  * @typedef {import('../logger').BaseLoggerType} BaseLoggerType
@@ -297,7 +298,10 @@ const FlowStageRecipes = {
           }
           result.totalPaymentDue += price;
         }
-        return result;
+        return {
+          ...result,
+          totalPaymentDue: fixCalculatedMoneyValue(result.totalPaymentDue),
+        };
       })();
       return {
         orderItems: fetchOpportunities.getOutput().orderItems,

packages/openactive-integration-tests/test/helpers/money-utils.js

@@ -0,0 +1,24 @@
+/**
+ * If performing calculations on money values, use this function on the final
+ * result to ensure that it does not accrue floating point errors.
+ *
+ * e.g.
+ *
+ * ```
+ * > 55.2 * 3
+ * 165.60000000000002
+ * > fixCalculatedMoneyValue(55.2 * 3)
+ * 165.6
+ * ```
+ *
+ * @param {number} valuePounds
+ * @returns {number}
+ */
+function fixCalculatedMoneyValue(valuePounds) {
+  const valuePence = valuePounds * 100;
+  return Math.round(valuePence) / 100;
+}
+
+module.exports = {
+  fixCalculatedMoneyValue,
+};