add test for --reduce-test (#3712)

test/input/reduce/input.js

@@ -0,0 +1,18 @@
+var _calls_ = 10, a = 100, b = 10, c = 0;
+
+function f0(b_1, a, undefined_2) {
+    a++ + ++b;
+    {
+        var expr2 = (b + 1 - .1 - .1 - .1 || a || 3).toString();
+        L20778: for (var key2 in expr2) {
+            (c = c + 1) + [ --b + b_1, typeof f0 == "function" && --_calls_ >= 0 && f0(--b + typeof (undefined_2 = 1 === 1 ? a : b), --b + {
+                c: (c = c + 1) + null
+            }, a++ + (typeof f0 == "function" && --_calls_ >= 0 && f0(typeof (c = 1 + c, 3 / "a" * ("c" >>> 23..toString()) >= (b_1 && (b_1[(c = c + 1) + a--] = (- -0,
+            true + {})))), 3, 25))), 1 === 1 ? a : b ];
+        }
+    }
+}
+
+var a_1 = f0([ , 0 ].length === 2);
+
+console.log(null, a, b, c, Infinity, NaN, undefined);

test/input/reduce/output.js

@@ -0,0 +1,15 @@
+var b = 0;
+
+function f0() {
+    var expr2 = (0 - 1 - .1 - .1).toString();
+    for (var key2 in expr2) {
+        --b;
+    }
+}
+
+var a_1 = f0();
+
+console.log(b);
+// output: -19
+// minify: -4
+// options: {"compress":{"unsafe_math":true},"mangle":false}

test/mocha/reduce.js

@@ -1,8 +1,26 @@
 var assert = require("assert");
 var exec = require("child_process").exec;
+var fs = require("fs");
 var reduce_test = require("../reduce");
 
+function read(path) {
+    return fs.readFileSync(path, "utf8");
+}
+
 describe("test/reduce.js", function() {
+    it("Should reduce test case", function() {
+        this.timeout(30000);
+        var result = reduce_test(read("test/input/reduce/input.js"), {
+            compress: {
+                unsafe_math: true,
+            },
+            mangle: false,
+        }, {
+            verbose: false,
+        });
+        if (result.error) throw result.error;
+        assert.strictEqual(result.code, read("test/input/reduce/output.js"));
+    });
     it("Should handle test cases with --toplevel", function() {
         var result = reduce_test([
             "var Infinity = 42;",