Add core tests to SavingsContract

mstable · Jan 2, 2021 · ced99c4 · ced99c4
1 parent b0cafc2
commit ced99c4
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Showing 4 changed files with 714 additions and 268 deletions.
diff --git a/.eslintrc.js b/.eslintrc.js
@@ -25,7 +25,8 @@ module.exports = {
         }
     },
     "rules": {
-        "@typescript-eslint/no-use-before-define": 1
+        "@typescript-eslint/no-use-before-define": 1,
+        "no-nested-ternary": 0
     },
     "overrides": [
         {

diff --git a/contracts/savings/SavingsContract.sol b/contracts/savings/SavingsContract.sol
@@ -111,15 +111,45 @@ contract SavingsContract is
     }
 
 
-    /** @dev Enable or disable the automation of fee collection during deposit process */
-    function automateInterestCollectionFlag(bool _enabled)
-        external
-        onlyGovernor
-    {
-        automateInterestCollection = _enabled;
-        emit AutomaticInterestCollectionSwitched(_enabled);
+    /***************************************
+                    VIEW - E
+    ****************************************/
+
+    /**
+     * @dev Returns the underlying balance of a given user
+     * @param _user     Address of the user to check
+     * @return balance  Units of underlying owned by the user
+     */
+    function balanceOfUnderlying(address _user) external view returns (uint256 balance) {
+        (balance,) = _creditsToUnderlying(balanceOf(_user));
+    }
+
+    /**
+     * @dev Converts a given underlying amount into credits
+     * @param _underlying  Units of underlying
+     * @return credits     Credit units (a.k.a imUSD)
+     */
+    function underlyingToCredits(uint256 _underlying) external view returns (uint256 credits) {
+        (credits,) = _underlyingToCredits(_underlying);
     }
 
+    /**
+     * @dev Converts a given credit amount into underlying
+     * @param _credits  Units of credits
+     * @return amount   Corresponding underlying amount
+     */
+    function creditsToUnderlying(uint256 _credits) external view returns (uint256 amount) {
+        (amount,) = _creditsToUnderlying(_credits);
+    }
+
+    // Deprecated in favour of `balanceOf(address)`
+    // Maintained for backwards compatibility
+    // Returns the credit balance of a given user
+    function creditBalances(address _user) external view returns (uint256) {
+        return balanceOf(_user);
+    }
+
+
     /***************************************
                     INTEREST
     ****************************************/
@@ -146,14 +176,22 @@ contract SavingsContract is
             // new exchange rate is relationship between _totalCredits & totalSavings
             // _totalCredits * exchangeRate = totalSavings
             // exchangeRate = totalSavings/_totalCredits
-            uint256 amountPerCredit = _calcExchangeRate(_amount, totalCredits);
-            uint256 newExchangeRate = exchangeRate.add(amountPerCredit);
+            (uint256 totalCollat, ) = _creditsToUnderlying(totalCredits);
+            uint256 newExchangeRate = _calcExchangeRate(totalCollat.add(_amount), totalCredits);
             exchangeRate = newExchangeRate;
 
             emit ExchangeRateUpdated(newExchangeRate, _amount);
         }
     }
 
+    /** @dev Enable or disable the automation of fee collection during deposit process */
+    function automateInterestCollectionFlag(bool _enabled)
+        external
+        onlyGovernor
+    {
+        automateInterestCollection = _enabled;
+        emit AutomaticInterestCollectionSwitched(_enabled);
+    }
 
     /***************************************
                     DEPOSIT
@@ -598,45 +636,6 @@ contract SavingsContract is
     }
 
 
-    /***************************************
-                    VIEW - E
-    ****************************************/
-
-    /**
-     * @dev Returns the underlying balance of a given user
-     * @param _user     Address of the user to check
-     * @return balance  Units of underlying owned by the user
-     */
-    function balanceOfUnderlying(address _user) external view returns (uint256 balance) {
-        (balance,) = _creditsToUnderlying(balanceOf(_user));
-    }
-
-    /**
-     * @dev Converts a given underlying amount into credits
-     * @param _underlying  Units of underlying
-     * @return credits     Credit units (a.k.a imUSD)
-     */
-    function underlyingToCredits(uint256 _underlying) external view returns (uint256 credits) {
-        (credits,) = _underlyingToCredits(_underlying);
-    }
-
-    /**
-     * @dev Converts a given credit amount into underlying
-     * @param _credits  Units of credits
-     * @return amount   Corresponding underlying amount
-     */
-    function creditsToUnderlying(uint256 _credits) external view returns (uint256 amount) {
-        (amount,) = _creditsToUnderlying(_credits);
-    }
-
-    // Deprecated in favour of `balanceOf(address)`
-    // Maintained for backwards compatibility
-    // Returns the credit balance of a given user
-    function creditBalances(address _user) external view returns (uint256) {
-        return balanceOf(_user);
-    }
-
-
     /***************************************
                     VIEW - I
     ****************************************/
@@ -661,7 +660,7 @@ contract SavingsContract is
 
     /**
      * @dev Converts masset amount into credits based on exchange rate
-     *               c = masset / exchangeRate
+     *               c = (masset / exchangeRate) + 1
      */
     function _underlyingToCredits(uint256 _underlying)
         internal
@@ -677,14 +676,14 @@ contract SavingsContract is
 
     /**
      * @dev Works out a new exchange rate, given an amount of collateral and total credits
-     *               e = underlying / credits
+     *               e = underlying / (credits-1)
      */
     function _calcExchangeRate(uint256 _totalCollateral, uint256 _totalCredits)
         internal
         pure
         returns (uint256 _exchangeRate)
     {
-        return _totalCollateral.divPrecisely(_totalCredits);
+        return _totalCollateral.divPrecisely(_totalCredits.sub(1));
     }
 
     /**

diff --git a/test-utils/assertions.ts b/test-utils/assertions.ts
@@ -71,7 +71,7 @@ export const assertBnGte = (actual: BN, comparison: BN): void => {
 export const assertBNSlightlyGT = (
     actual: BN,
     equator: BN,
-    maxActualShouldExceedExpected = new BN(100),
+    maxActualShouldExceedExpected: number | BN = new BN(100),
     mustBeGreater = false,
 ): void => {
     const actualDelta = actual.gt(equator) ? actual.sub(equator) : equator.sub(actual);
@@ -81,7 +81,7 @@ export const assertBNSlightlyGT = (
         `Actual value should be greater than the expected value`,
     );
     assert.ok(
-        actual.lte(equator.add(maxActualShouldExceedExpected)),
+        actual.lte(equator.add(new BN(maxActualShouldExceedExpected))),
         `Actual value should not exceed ${maxActualShouldExceedExpected.toString()} units greater than expected. Variance was ${actualDelta.toString()}`,
     );
 };