Mutation coverage: IMPL-div-extremes

test/src/lib/implementation/LibDecimalFloatImplementation.div.t.sol

@@ -185,6 +185,17 @@ contract LibDecimalFloatImplementationDivTest is Test {
         this.divExternal(1e76, 76, 1, type(int256).min + 76);
     }
 
+    /// A positive dividend over a negative power of ten divisor, with the
+    /// quotient exponent exactly `type(int256).max`: `1e76 10^(max - 76)` over
+    /// `-1 10^-76` is exactly `-1e76 10^max`, which needs no shed digit, so it
+    /// returns. Only a `type(int256).min` dividend there has a 2^255 quotient.
+    function testDivNegativePowerOfTenDivisorAtMax() external pure {
+        int256 max = type(int256).max;
+        checkDiv(1e76, max - 76, -1, -76, -1e76, max);
+        checkDiv(-1e76, max - 76, -1, -76, 1e76, max);
+        checkDiv(type(int256).max, max - 76, -1, -76, -type(int256).max, max);
+    }
+
     /// An unfull divisor at the floor overflows the quotient exponent for a
     /// numerator with a non-negative maximized exponent.
     function testDivUnfullDivisorExponentOverflow() external {

test/src/lib/implementation/LibDecimalFloatImplementation.mainEquivalence.t.sol

@@ -538,15 +538,22 @@ contract LibDecimalFloatImplementationMainEquivalenceTest is Test {
         // #368: a positive 2^255 quotient below the floor, by each scale,
         // down to the last digit it keeps.
         for (int256 u = 1; u <= 76; u++) {
-            assertDiffers(
-                abi.encodeCall(this.mainDiv, (min, min + 76, -1e76, u)),
-                abi.encodeCall(this.prDiv, (min, min + 76, -1e76, u))
-            );
-            checkDiv(min, min + 76, -1e76, u);
-            checkDiv(min, min + 75, -1e75, u);
+            this.checkDivMinByMinusScaleBelowFloor(u);
         }
     }
 
+    /// One shed of the #368 loop, in its own call frame so memory does not
+    /// accumulate across the 76 sheds.
+    function checkDivMinByMinusScaleBelowFloor(int256 u) external view {
+        int256 min = type(int256).min;
+        assertDiffers(
+            abi.encodeCall(this.mainDiv, (min, min + 76, -1e76, u)),
+            abi.encodeCall(this.prDiv, (min, min + 76, -1e76, u))
+        );
+        checkDiv(min, min + 76, -1e76, u);
+        checkDiv(min, min + 75, -1e75, u);
+    }
+
     function testMainEquivalenceAddFloorExamples() external view {
         int256 min = type(int256).min;
         assertDiffers(abi.encodeCall(this.mainAdd, (1, min, 1, min)), abi.encodeCall(this.prAdd, (1, min, 1, min)));