From 9b0b1900197882cdcd8e768fb057fef1e4897b45 Mon Sep 17 00:00:00 2001
From: emilio <emilio@ethlend.io>
Date: Tue, 11 Aug 2020 10:11:35 +0200
Subject: [PATCH] Fixed compounded interest approximation

---
 contracts/libraries/MathUtils.sol  | 3 ++-
 test/helpers/utils/calculations.ts | 6 +++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/contracts/libraries/MathUtils.sol b/contracts/libraries/MathUtils.sol
index 7b0a8f32..1e26366d 100644
--- a/contracts/libraries/MathUtils.sol
+++ b/contracts/libraries/MathUtils.sol
@@ -57,7 +57,8 @@ library MathUtils {
     }
 
      uint256 expMinusOne = exp.sub(1);
-     uint256 expMinusTwo = exp.sub(2);
+
+     uint256 expMinusTwo = exp > 2 ? exp.sub(2) : 0;
 
     uint256 ratePerSecond = _rate.div(31536000);
      
diff --git a/test/helpers/utils/calculations.ts b/test/helpers/utils/calculations.ts
index 2d5a6282..34c25069 100644
--- a/test/helpers/utils/calculations.ts
+++ b/test/helpers/utils/calculations.ts
@@ -1265,8 +1265,12 @@ const calcCompoundedInterest = (
 
   const timeDifference = currentTimestamp.minus(lastUpdateTimestamp);
 
+  if(timeDifference.eq(0)){
+    return new BigNumber(RAY);
+  }
+
   const expMinusOne = timeDifference.minus(1);
-  const expMinusTwo = timeDifference.minus(2);
+  const expMinusTwo = timeDifference.gt(2) ? timeDifference.minus(2) : 0;
 
   const ratePerSecond = rate.div(ONE_YEAR);