From f6efc2597b4a647b8027252b58bb84b47ccdacd2 Mon Sep 17 00:00:00 2001
From: Denali Marsh <denali@kava.io>
Date: Tue, 12 Jan 2021 10:03:09 +0100
Subject: [PATCH] Hard: investigate sdk.RelativePow runtime panic  (#762)

* interest rate practical test

* add clarification comment
---
 x/hard/keeper/interest_test.go | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/x/hard/keeper/interest_test.go b/x/hard/keeper/interest_test.go
index 2bbedf63..05e65523 100644
--- a/x/hard/keeper/interest_test.go
+++ b/x/hard/keeper/interest_test.go
@@ -289,8 +289,6 @@ func (suite *InterestTestSuite) TestCalculateBorrowInterestFactor() {
 				expectedValue:         sdk.MustNewDecFromStr("40628388.864535408465693310"),
 			},
 		},
-		// If we raise the per second interest rate too much we'll cause an integer overflow.
-		// For example, perSecondInterestRate: '1.000005555555' will cause a panic.
 		{
 			"1 year: highest interest rate",
 			args{
@@ -299,6 +297,14 @@ func (suite *InterestTestSuite) TestCalculateBorrowInterestFactor() {
 				expectedValue:         sdk.MustNewDecFromStr("2017093013158200407564.613502861572552603"),
 			},
 		},
+		{
+			"largest per second interest rate with practical elapsed time",
+			args{
+				perSecondInterestRate: sdk.MustNewDecFromStr("18.445"), // Begins to panic at ~18.45 (1845%/second interest rate)
+				timeElapsed:           sdk.NewInt(30),                  // Assume a 30 second period, longer than any expected individual block
+				expectedValue:         sdk.MustNewDecFromStr("94702138679846565921082258202543002089.215969366091911769"),
+			},
+		},
 	}
 
 	for _, tc := range testCases {