fix: example in tests

src/test/ExcessivelySafeCall.t.sol

@@ -8,6 +8,7 @@ contract ContractTest is DSTest {
     using ExcessivelySafeCall for address;
 
     address target;
+    Intermediary intermediary;
     CallTarget t;
 
     function returnSize() internal pure returns (uint256 _bytes) {
@@ -19,6 +20,7 @@ contract ContractTest is DSTest {
     function setUp() public {
         t = new CallTarget();
         target = address(t);
+        intermediary = new Intermediary();
     }
 
     function testCall() public {
@@ -177,9 +179,38 @@ contract ContractTest is DSTest {
         assertEq(_ret.length, 32, "revert didn't truncate");
     }
 
+    function test_drain() public {
+        intermediary.getDrained{gas: 1_000_000}(target, 10_000);
+    }
+
+    function test_drain_safe() public {
+        intermediary.getSafeDrained{gas: 1_000_000}(target, 10_000);
+    }
 }
 
 
+contract Intermediary {
+    using ExcessivelySafeCall for address;
+    function getDrained(address target, uint256 drainTo) public {
+        bool _success;
+        bytes memory _ret;
+        (_success, _ret) = target.call(
+            abi.encodeWithSelector(CallTarget.drainTo.selector, drainTo)
+        );
+    }
+
+    function getSafeDrained(address target, uint256 drainTo) public {
+        bool _success;
+        bytes memory _ret;
+        (_success, _ret) = target.excessivelySafeCall(
+            gasleft(),
+            0,
+            0,
+            abi.encodeWithSelector(CallTarget.drainTo.selector, drainTo)
+        );
+    }
+}
+
 contract CallTarget {
     uint256 public called;
     constructor () {}
@@ -219,4 +250,15 @@ contract CallTarget {
     function badRev() external pure {
         revBytes(1_000_000);
     }
+
+    function drainTo(uint256 gas) public view {
+        uint256 len;
+        while (gasleft() > gas) {
+            bytes memory a = new bytes(0);
+            len += 32 + a.length;
+        }
+        assembly {
+            return (0, len)
+        }
+    }
 }