(Medium) - How TDD Can Prevent Over-Engineering

SingleInterestAmountReturn.diff

     const greaterThan5000 = { endOfRange: Money('$5000.00'), interestPerDollar: Money('$0.14'), previousInterestPerDollar: Money('$0.09') };
     const greaterThan10000 = { endOfRange: Money('$10000.00'), interestPerDollar: Money('$0.21'), previousInterestPerDollar: Money('$0.14') };
 
-    if (loanAmount.greaterThan(Money('$2000.00')) && loanAmount.lessThan(Money('$5001.00'))) {
-      let interestAmount = Money('$0.00');
+    let interestAmount = Money('$0.00');
 
+    if (loanAmount.greaterThan(Money('$2000.00')) && loanAmount.lessThan(Money('$5001.00'))) {
       interestAmount = interestAmount.plus(calculateInterest(loanAmount, greaterThan2000));
-
-      return interestAmount;
     }
 
     if (loanAmount.greaterThan(Money('$5000.00')) && loanAmount.lessThan(Money('$10001.00'))) {
-      let interestAmount = Money('$0.00');
-
       interestAmount = interestAmount.plus(calculateInterest(loanAmount, greaterThan2000));
       interestAmount = interestAmount.plus(calculateInterest(loanAmount, greaterThan5000));
-
-      return interestAmount;
     }
 
     if (loanAmount.greaterThan(Money('$10000.00'))) {
-      let interestAmount = Money('$0.00');
-
       interestAmount = interestAmount.plus(calculateInterest(loanAmount, greaterThan2000));
       interestAmount = interestAmount.plus(calculateInterest(loanAmount, greaterThan5000));
       interestAmount = interestAmount.plus(calculateInterest(loanAmount, greaterThan10000));
-
-      return interestAmount;
     }
 
-    return Money('$0.00');
+    return interestAmount;
   };
 
   QUnit.module('Loans of $2000 and below are interest-free. For example');