implement test/sandbox.js (#1749)

- `test/run-tests.js` and `test/ufuzz.js` now shares the same `run_code()` and `same_stdout()`
- re-enable fuzzer to generate top-level `NaN`, `Infinity` & `undefined`
- attempt to show beautified output only when `run_code()` output is preserved

test/sandbox.js

@@ -0,0 +1,50 @@
+var vm = require("vm");
+
+var FUNC_TOSTRING = [
+    "Function.prototype.toString = Function.prototype.valueOf = function() {",
+    "    var ids = [];",
+    "    return function() {",
+    "        var i = ids.indexOf(this);",
+    "        if (i < 0) {",
+    "            i = ids.length;",
+    "            ids.push(this);",
+    "        }",
+    '        return "[Function: __func_" + i + "__]";',
+    "    }",
+    "}();",
+    ""
+].join("\n");
+exports.run_code = function(code) {
+    var stdout = "";
+    var original_write = process.stdout.write;
+    process.stdout.write = function(chunk) {
+        stdout += chunk;
+    };
+    try {
+        new vm.Script(FUNC_TOSTRING + code).runInNewContext({
+            console: {
+                log: function() {
+                    return console.log.apply(console, [].map.call(arguments, function(arg) {
+                        return typeof arg == "function" ? arg.toString() : arg;
+                    }));
+                }
+            }
+        }, { timeout: 30000 });
+        return stdout;
+    } catch (ex) {
+        return ex;
+    } finally {
+        process.stdout.write = original_write;
+    }
+};
+exports.same_stdout = ~process.version.lastIndexOf("v0.12.", 0) ? function(expected, actual) {
+    if (typeof expected != typeof actual) return false;
+    if (typeof expected != "string") {
+        if (expected.name != actual.name) return false;
+        expected = expected.message.slice(expected.message.lastIndexOf("\n") + 1);
+        actual = actual.message.slice(actual.message.lastIndexOf("\n") + 1);
+    }
+    return expected == actual;
+} : function(expected, actual) {
+    return typeof expected == typeof actual && expected.toString() == actual.toString();
+};