Add SafeMath test showing testing for revert

remix-tests/tests/examples_4/SafeMath.sol

+// Copyright (c) 2016 Smart Contract Solutions, Inc.
+
+pragma solidity ^0.4.24;
+
+
+/**
+ * @title SafeMath
+ * @dev Math operations with safety checks that revert on error
+ */
+library SafeMath {
+
+  /**
+  * @dev Multiplies two numbers, reverts on overflow.
+  */
+  function mul(uint256 _a, uint256 _b) internal pure returns (uint256) {
+    // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
+    // benefit is lost if 'b' is also tested.
+    // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
+    if (_a == 0) {
+      return 0;
+    }
+
+    uint256 c = _a * _b;
+    require(c / _a == _b);
+
+    return c;
+  }
+
+  /**
+  * @dev Integer division of two numbers truncating the quotient, reverts on division by zero.
+  */
+  function div(uint256 _a, uint256 _b) internal pure returns (uint256) {
+    require(_b > 0); // Solidity only automatically asserts when dividing by 0
+    uint256 c = _a / _b;
+    // assert(_a == _b * c + _a % _b); // There is no case in which this doesn't hold
+
+    return c;
+  }
+
+  /**
+  * @dev Subtracts two numbers, reverts on overflow (i.e. if subtrahend is greater than minuend).
+  */
+  function sub(uint256 _a, uint256 _b) internal pure returns (uint256) {
+    require(_b <= _a);
+    uint256 c = _a - _b;
+
+    return c;
+  }
+
+  /**
+  * @dev Adds two numbers, reverts on overflow.
+  */
+  function add(uint256 _a, uint256 _b) internal pure returns (uint256) {
+    uint256 c = _a + _b;
+    require(c >= _a);
+
+    return c;
+  }
+
+  /**
+  * @dev Divides two numbers and returns the remainder (unsigned integer modulo),
+  * reverts when dividing by zero.
+  */
+  function mod(uint256 a, uint256 b) internal pure returns (uint256) {
+    require(b != 0);
+    return a % b;
+  }
+}

remix-tests/tests/examples_4/SafeMathProxy.sol

+pragma solidity ^0.4.24;
+import "./SafeMath.sol";
+
+/*
+Using a proxy contract here allows revert-causing functions that contain
+require() to return false rather than halt execution
+https://truffleframework.com/tutorials/testing-for-throws-in-solidity-tests
+*/
+contract SafeMathProxy {
+    using SafeMath for uint;
+
+    function divProxy(uint256 a, uint256 b) returns (uint256) {
+        return a.div(b);
+    }
+
+    function mulProxy(uint256 a, uint256 b) returns (uint256) {
+        return a.mul(b);
+    }
+
+    function subProxy(uint256 a, uint256 b) returns (uint256) {
+        return a.sub(b);
+    }
+
+    function addProxy(uint256 a, uint256 b) returns (uint256) {
+        return a.add(b);
+    }
+
+    function modProxy(uint256 a, uint256 b) returns (uint256) {
+        return a.mod(b);
+    }
+}

remix-tests/tests/examples_4/SafeMath_test.sol

+pragma solidity ^0.4.24;
+import "./tests.sol";
+import "./SafeMath.sol";
+import "./SafeMathProxy.sol";
+
+contract SafeMathTest {
+  SafeMathProxy safemathproxy;
+
+  function beforeAll() {
+    safemathproxy = new SafeMathProxy();
+  }
+
+  function unsafeMultiplicationShouldOverflow() public constant returns (bool) {
+    uint256 a = 4;
+    uint256 b = 2 ** 256 - 1;
+    return Assert.equal(
+      a * b,
+      2 ** 256 - 4,
+      "unsafe multiplication did not overflow"
+    );
+  }
+
+  function safeMultiplicationShouldRevert() public constant returns (bool) {
+    uint256 a = 4;
+    uint256 b = 2 ** 256 - 1;
+    return Assert.equal(
+      address(safemathproxy).call.gas(40000).value(0)("mulProxy",[a, b]),
+      false,
+      "safe multiplication did not revert"
+    );
+  }
+
+  function safeDivisionByZeroShouldRevert() public constant returns (bool) {
+    uint256 a = 4;
+    uint256 b = 0;
+    return Assert.equal(
+      address(safemathproxy).call.gas(40000).value(0)("divProxy", [a, b]),
+      false,
+      "safe division did not revert"
+    );
+  }
+
+  function unsafeSubtractShouldUnderflow() public constant returns (bool) {
+    uint256 a = 0;
+    uint256 b = a - 1;
+    return Assert.equal(
+      b,
+      2 ** 256 - 1,
+      "unsafe subtraction did not underflow"
+    );
+  }
+
+  function safeSubtractShouldRevert() public constant returns (bool) {
+    return Assert.equal(
+      address(safemathproxy).call.gas(40000).value(0)("subProxy", [0, 1]),
+      false,
+      "safe subtract should revert"
+    );
+  }
+
+  function unsafeAdditionShouldOverflow() public constant returns (bool) {
+    uint256 a = 1;
+    uint256 b = 2 ** 256 - 1;
+    return Assert.equal(a + b, 0, "unsafe addition did not overflow");
+  }
+
+  function safeAdditionShouldRevert() public constant returns (bool) {
+    uint256 a = 1;
+    uint256 b = 2 ** 256 - 1;
+    return Assert.equal(
+      address(safemathproxy).call.gas(40000).value(0)("addProxy", [a, b]),
+      false,
+      "safe addition should revert"
+    );
+  }
+
+  function safeModulusShouldRevert() public constant returns (bool) {
+    uint256 a = 1;
+    uint256 b = 0;
+    return Assert.equal(
+      address(safemathproxy).call.gas(40000).value(0)("modProxy", [a, b]),
+      false,
+      "safe modulus did not revert"
+    );
+  }
+}