                                         hookedFree: testReserveCapacityLarger_freeHook,
                                         hookedMemcpy: testReserveCapacityLarger_memcpyHook)
         var buf = alloc.buffer(capacity: 16)
-        let bufCopy = buf
+        var bufCopy = buf
 
         withExtendedLifetime(bufCopy) {
             let oldCapacity = buf.capacity

            XCTAssertNotEqual(buf.capacity, oldCapacity)
            XCTAssertNotEqual(oldPtrVal, newPtrVal)
        }
    }

    func testReserveCapacityWithMinimumWritableBytesWhenNotEnoughWritableBytes() {

            }
            XCTAssertNil(secondResult)
            XCTAssertNil(thirdResult)
            localCopy.writeString("foo") // stops the optimiser getting rid of `localCopy`
        }

        let fourthResult = buffer.modifyIfUniquelyOwned {
