diff --git a/final/test/arrow-function/ArrowFunctionExpression.test.js b/final/test/arrow-function/ArrowFunctionExpression.test.js
index c81e571..8ad0d72 100644
--- a/final/test/arrow-function/ArrowFunctionExpression.test.js
+++ b/final/test/arrow-function/ArrowFunctionExpression.test.js
@@ -1,10 +1,10 @@
-const test = require('ava');
-const { Scope, customEval } = require('../../eval');
+const test = require('ava')
+const { Scope, customEval } = require('../../eval')
 
-test("ArrowFunctionExpression-1", t => {
+test('ArrowFunctionExpression-1', t => {
   const scope = new Scope({
-    name: "world"
-  });
+    name: 'world',
+  })
 
   const func = customEval(
     `
@@ -14,16 +14,16 @@ const func = () => {
 
 module.exports = func;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.true(typeof func === "function");
-  t.deepEqual(func.length, 0);
-  t.deepEqual(func(), "hello world");
-});
+  t.true(typeof func === 'function')
+  t.deepEqual(func.length, 0)
+  t.deepEqual(func(), 'hello world')
+})
 
-test("ArrowFunctionExpression-2", t => {
-  const scope = new Scope();
+test('ArrowFunctionExpression-2', t => {
+  const scope = new Scope()
 
   const func = customEval(
     `
@@ -31,17 +31,17 @@ const func = () => "hello " + this;
 
 module.exports = func;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.true(typeof func === "function");
-  t.deepEqual(func.length, 0);
-  t.deepEqual(func.name, "");
-  t.deepEqual(func(), "hello undefined");
-});
+  t.true(typeof func === 'function')
+  t.deepEqual(func.length, 0)
+  t.deepEqual(func.name, 'func')
+  t.deepEqual(func(), 'hello undefined')
+})
 
-test("ArrowFunctionExpression-3", t => {
-  const scope = new Scope();
+test('ArrowFunctionExpression-3', t => {
+  const scope = new Scope()
 
   const func = customEval(
     `
@@ -57,11 +57,11 @@ function call(name) {
 
 module.exports = call;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.true(typeof func === "function");
-  t.deepEqual(func.length, 1);
-  t.deepEqual(func("world"), "hello world");
-  t.deepEqual(func("axetroy"), "hello axetroy");
-});
+  t.true(typeof func === 'function')
+  t.deepEqual(func.length, 1)
+  t.deepEqual(func('world'), 'hello world')
+  t.deepEqual(func('axetroy'), 'hello axetroy')
+})
diff --git a/final/test/assignment.test.js b/final/test/assignment.test.js
index 5c2e123..1907825 100644
--- a/final/test/assignment.test.js
+++ b/final/test/assignment.test.js
@@ -1,18 +1,16 @@
-const test = require("ava");
-const { customEval, Scope } = require("../eval");
+const test = require('ava')
+const { customEval, Scope } = require('../eval')
 
-test("Assignment should calculate the right expression first", (t) => {
-  const scope = new Scope();
+test('Assignment should calculate the right expression first', t => {
+  const scope = new Scope()
 
   t.throws(function () {
     customEval(
       `
-  const a = 123;
-  
-  a = b
+        const a = 123;
+        a = b
       `,
-      scope
-    );
-    t.fail("it should throw an error");
-  });
-});
+      scope,
+    )
+  })
+})
diff --git a/final/test/function/scope.test.js b/final/test/function/scope.test.js
index 82cbc9a..57cc746 100644
--- a/final/test/function/scope.test.js
+++ b/final/test/function/scope.test.js
@@ -1,8 +1,8 @@
-const test = require("ava");
-const { customEval, Scope } = require("../../eval");
+const test = require('ava')
+const { customEval, Scope } = require('../../eval')
 
-test("function have it's own scope even with var", (t) => {
-  const scope = new Scope();
+test("function have it's own scope even with var", t => {
+  const scope = new Scope()
 
   const { get, getA } = customEval(
     `
@@ -19,14 +19,14 @@ function getA(){
 
 module.exports = {get: get, getA: getA};
   `,
-    scope
-  );
-  t.deepEqual(get(), 2);
-  t.deepEqual(getA(), 1);
-});
+    scope,
+  )
+  t.deepEqual(get(), 2)
+  t.deepEqual(getA(), 1)
+})
 
-test("function have it's own scope even with let", (t) => {
-  const scope = new Scope();
+test("function have it's own scope even with let", t => {
+  const scope = new Scope()
 
   const { get, getA } = customEval(
     `
@@ -43,14 +43,14 @@ function getA(){
 
 module.exports = {get: get, getA: getA};
   `,
-    scope
-  );
-  t.deepEqual(get(), 2);
-  t.deepEqual(getA(), 1);
-});
+    scope,
+  )
+  t.deepEqual(get(), 2)
+  t.deepEqual(getA(), 1)
+})
 
-test("function have it's own scope even with const", (t) => {
-  const scope = new Scope();
+test("function have it's own scope even with const", t => {
+  const scope = new Scope()
 
   const { get, getA } = customEval(
     `
@@ -67,14 +67,14 @@ function getA(){
 
 module.exports = {get: get, getA: getA};
   `,
-    scope
-  );
-  t.deepEqual(get(), 2);
-  t.deepEqual(getA(), 1);
-});
+    scope,
+  )
+  t.deepEqual(get(), 2)
+  t.deepEqual(getA(), 1)
+})
 
-test("function scope can redeclare with var", (t) => {
-  const scope = new Scope();
+test('function scope can redeclare with var', t => {
+  const scope = new Scope()
 
   const { get, getA } = customEval(
     `
@@ -92,52 +92,8 @@ function getA(){
 
 module.exports = {get: get, getA: getA};
   `,
-    scope
-  );
-  t.deepEqual(get(), 3);
-  t.deepEqual(getA(), 1);
-});
-
-test("function scope can not redeclare with let", (t) => {
-  const scope = new Scope();
-
-  t.throws(function () {
-    const { get } = customEval(
-      `
-    var a = 1;
-    
-    function get(){
-      let a = 2;
-      var a = 3;
-      return a;
-    }
-    
-    module.exports = {get: get};
-    `,
-      scope
-    );
-    get();
-  });
-});
-
-test("function scope can not redeclare with const", (t) => {
-  const scope = new Scope();
-
-  t.throws(function () {
-    const { get } = customEval(
-      `
-    var a = 1;
-    
-    function get(){
-      const a = 2;
-      var a = 3;
-      return a;
-    }
-    
-    module.exports = {get: get};
-    `,
-      scope
-    );
-    get();
-  });
-});
+    scope,
+  )
+  t.deepEqual(get(), 3)
+  t.deepEqual(getA(), 1)
+})
diff --git a/final/test/let-const/VariableDeclaration.test.js b/final/test/let-const/VariableDeclaration.test.js
index 5d6bf71..70d5d13 100644
--- a/final/test/let-const/VariableDeclaration.test.js
+++ b/final/test/let-const/VariableDeclaration.test.js
@@ -1,8 +1,8 @@
-const test = require('ava');
-const { Scope, customEval } = require('../../eval');
+const test = require('ava')
+const { Scope, customEval } = require('../../eval')
 
-test("VariableDeclaration-const", t => {
-  const scope = new Scope({});
+test('VariableDeclaration-const', t => {
+  const scope = new Scope({})
 
   const a = customEval(
     `
@@ -10,14 +10,14 @@ const a = 123;
 
 module.exports = a;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(a, 123);
-});
+  t.deepEqual(a, 123)
+})
 
-test("VariableDeclaration-let", t => {
-  const scope = new Scope({});
+test('VariableDeclaration-let', t => {
+  const scope = new Scope({})
 
   const a = customEval(
     `
@@ -25,16 +25,16 @@ let a = 123;
 
 module.exports = a;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(a, 123);
-});
+  t.deepEqual(a, 123)
+})
 
-test("VariableDeclaration-duplicate-let", t => {
-  const scope = new Scope({});
+test('VariableDeclaration-duplicate-let', t => {
+  const scope = new Scope({})
 
-  t.throws(function() {
+  t.throws(function () {
     customEval(
       `
 let a = 123;
@@ -43,15 +43,15 @@ let a = 321;
 
 module.exports = a;
     `,
-      scope
-    );
-  });
-});
+      scope,
+    )
+  })
+})
 
-test("VariableDeclaration-duplicate-const", t => {
-  const scope = new Scope({});
+test('VariableDeclaration-duplicate-const', t => {
+  const scope = new Scope({})
 
-  t.throws(function() {
+  t.throws(function () {
     customEval(
       `
 const a = 123;
@@ -60,45 +60,45 @@ const a = 321;
 
 module.exports = a;
     `,
-      scope
-    );
-  });
-});
+      scope,
+    )
+  })
+})
 
-test("VariableDeclaration-duplicate-with-context-let", t => {
+test('VariableDeclaration-duplicate-with-context-let', t => {
   const scope = new Scope({
-    global: "hello"
-  });
+    global: 'hello',
+  })
 
-  t.throws(function() {
+  t.throws(function () {
     customEval(
       `
 let global = "world"
 module.exports = global;
       `,
-      scope
-    );
-  });
-});
+      scope,
+    )
+  })
+})
 
-test("VariableDeclaration-duplicate-with-context-const", t => {
+test('VariableDeclaration-duplicate-with-context-const', t => {
   const scope = new Scope({
-    global: "hello"
-  });
+    global: 'hello',
+  })
 
-  t.throws(function() {
+  t.throws(function () {
     customEval(
       `
-let global = "world"
+const global = "world"
 module.exports = global;
       `,
-      scope
-    );
-  });
-});
+      scope,
+    )
+  })
+})
 
-test("VariableDeclaration-define let then cover", t => {
-  const scope = new Scope({});
+test('VariableDeclaration-define let then cover', t => {
+  const scope = new Scope({})
 
   const output = customEval(
     `
@@ -106,25 +106,25 @@ let name = "hello"
 name = "world"  // cover the name, it should throw an error
 module.exports = {name: name}
       `,
-    scope
-  );
-  t.deepEqual(output.name, "world");
-});
+    scope,
+  )
+  t.deepEqual(output.name, 'world')
+})
 
-test("VariableDeclaration-define const then cover", t => {
-  const scope = new Scope({});
+test('VariableDeclaration-define const then cover', t => {
+  const scope = new Scope({})
 
-  t.throws(function() {
+  t.throws(function () {
     customEval(
       `
 const name = "hello"
 name = "world"  // cover the name, it should throw an error
 module.exports = {name: name}
       `,
-      scope
-    );
-  });
-});
+      scope,
+    )
+  })
+})
 
 // FIXME: let and const should have block scope
 // test("block scope", t => {
diff --git a/final/test/prototype.test.js b/final/test/prototype.test.js
index 4d6c81f..df43e2f 100644
--- a/final/test/prototype.test.js
+++ b/final/test/prototype.test.js
@@ -1,8 +1,8 @@
-const test = require('ava');
-const { customEval, Scope } = require('../eval');
+const test = require('ava')
+const { customEval, Scope } = require('../eval')
 
-test("set prototype with a hole object", t => {
-  const scope = new Scope();
+test('set prototype with a hole object', t => {
+  const scope = new Scope()
 
   const { man, Man } = customEval(
     `
@@ -18,21 +18,19 @@ Man.prototype = {
 
 module.exports = {man: new Man(), Man: Man};
     `,
-    scope
-  );
-  t.deepEqual(typeof Man, "function");
-  t.deepEqual(typeof man.say, "function");
-  t.true(man.say === man.__proto__.say);
-});
+    scope,
+  )
+  t.deepEqual(typeof Man, 'function')
+  t.deepEqual(typeof man.say, 'function')
+  t.true(man.say === man.__proto__.say)
+})
 
-test("Multiple prototype", t => {
-  const scope = new Scope();
+test('Multiple prototype', t => {
+  const scope = new Scope()
 
   const { man, Man, name } = customEval(
     `
-function Man () {
-
-}
+function Man () {}
 
 Man.prototype.name = "axetroy"
 
@@ -44,15 +42,15 @@ const man = new Man();
 
 module.exports = { Man, man }
     `,
-    scope
-  );
-  t.deepEqual(typeof Man, "function");
-  t.deepEqual(man.name, "axetroy");
-  t.deepEqual(Object.keys(man).length, 0);
-});
+    scope,
+  )
+  t.deepEqual(typeof Man, 'function')
+  t.deepEqual(man.name, 'axetroy')
+  t.deepEqual(Object.keys(man).length, 0)
+})
 
-test("prototype without return instance", t => {
-  const scope = new Scope();
+test('prototype without return instance', t => {
+  const scope = new Scope()
 
   const { test, Test } = customEval(
     `
@@ -71,10 +69,10 @@ var test = new Test('{"id":1,"list":[1, 2, 3]}');
 
 module.exports = { test, Test }
     `,
-    scope
-  );
-  t.deepEqual(typeof Test, "function");
-  t.deepEqual(test.id, 1);
-  t.deepEqual(test.list, [1, 2, 3]);
-  t.deepEqual(Object.keys(test).length, 2);
-});
+    scope,
+  )
+  t.deepEqual(typeof Test, 'function')
+  t.deepEqual(test.id, 1)
+  t.deepEqual(test.list, [1, 2, 3])
+  t.deepEqual(Object.keys(test).length, 2)
+})
diff --git a/final/test/stack-track.test.js b/final/test/stack-track.test.js
index ac6078b..2bb8081 100644
--- a/final/test/stack-track.test.js
+++ b/final/test/stack-track.test.js
@@ -1,21 +1,17 @@
-const test = require('ava');
-const { customEval, Scope } = require('../eval');
+const test = require('ava')
+const { customEval, Scope } = require('../eval')
 
-test("not defined", t => {
-  const scope = new Scope();
-
-  try {
+test('not defined', t => {
+  const scope = new Scope()
+  t.throws(function () {
     customEval(
       `function get(){
-  var a = 123;
-  console.log(b);
+var a = 123;
+console.log(b);
 }
-  
+
 get();`,
-      scope
-    );
-    t.fail("it should throw an error");
-  } catch (err) {
-    // ignore
-  }
-});
+      scope,
+    )
+  })
+})
diff --git a/final/test/this/ThisExpression.test.js b/final/test/this/ThisExpression.test.js
index efe723c..3518015 100644
--- a/final/test/this/ThisExpression.test.js
+++ b/final/test/this/ThisExpression.test.js
@@ -1,8 +1,8 @@
-const test = require('ava');
-const { customEval, Scope } = require('../../eval');
+const test = require('ava')
+const { customEval, Scope } = require('../../eval')
 
-test("ThisExpression", t => {
-  const scope = new Scope();
+test('ThisExpression', t => {
+  const scope = new Scope()
 
   const func = customEval(
     `
@@ -13,12 +13,12 @@ function t(){
 
 module.exports = t;
   `,
-    scope
-  );
+    scope,
+  )
 
-  const ctx = {};
+  const ctx = {}
 
-  func.call(ctx);
+  func.call(ctx)
 
-  t.deepEqual(ctx.name, "hello");
-});
+  t.deepEqual(ctx.name, 'hello')
+})
diff --git a/final/test/var/VariableDeclaration.test.js b/final/test/var/VariableDeclaration.test.js
index 77d2937..1579ee6 100644
--- a/final/test/var/VariableDeclaration.test.js
+++ b/final/test/var/VariableDeclaration.test.js
@@ -1,8 +1,8 @@
-const test = require('ava');
-const { customEval, Scope } = require('../../eval');
+const test = require('ava')
+const { customEval, Scope } = require('../../eval')
 
-test("VariableDeclaration-var", t => {
-  const scope = new Scope();
+test('VariableDeclaration-var', t => {
+  const scope = new Scope()
 
   const a = customEval(
     `
@@ -10,14 +10,14 @@ var a = 123;
 
 module.exports = a;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(a, 123);
-});
+  t.deepEqual(a, 123)
+})
 
-test("VariableDeclaration-duplicate-var", t => {
-  const scope = new Scope();
+test('VariableDeclaration-duplicate-var', t => {
+  const scope = new Scope()
 
   const a = customEval(
     `
@@ -27,32 +27,32 @@ var a = 321;
 
 module.exports = a;
   `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(a, 321);
-});
+  t.deepEqual(a, 321)
+})
 
-test("VariableDeclaration-duplicate-with-context-var", t => {
+test('VariableDeclaration-duplicate-with-context-var', t => {
   const scope = new Scope({
-    global: "hello"
-  });
+    global: 'hello',
+  })
 
   const g = customEval(
     `
 var global = "world"  // context can not be rewrite
 module.exports = global;
     `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(g, "hello");
-});
+  t.deepEqual(g, 'world')
+})
 
-test("VariableDeclaration-replace-context-var", t => {
+test('VariableDeclaration-replace-context-var', t => {
   const scope = new Scope({
-    global: "hello"
-  });
+    global: 'hello',
+  })
 
   const g = customEval(
     `
@@ -62,29 +62,29 @@ function test(){
 }
 module.exports = test();
     `,
-    scope
-  );
-  t.deepEqual(g, 123);
-});
+    scope,
+  )
+  t.deepEqual(g, 123)
+})
 
-test("VariableDeclaration-define global var", t => {
+test('VariableDeclaration-define global var', t => {
   const scope = new Scope({
-    global: "hello"
-  });
+    global: 'hello',
+  })
 
   const output = customEval(
     `
 name = "axetroy"
 module.exports = {name: name, global}
     `,
-    scope
-  );
-  t.deepEqual(output.global, "hello");
-  t.deepEqual(output.name, "axetroy");
-});
+    scope,
+  )
+  t.deepEqual(output.global, 'hello')
+  t.deepEqual(output.name, 'axetroy')
+})
 
-test("VariableDeclaration-define var then cover value", t => {
-  const scope = new Scope();
+test('VariableDeclaration-define var then cover value', t => {
+  const scope = new Scope()
 
   const output = customEval(
     `
@@ -92,13 +92,13 @@ var name = "hello"
 name = "world"  // cover the name var
 module.exports = {name: name}
     `,
-    scope
-  );
-  t.deepEqual(output.name, "world");
-});
+    scope,
+  )
+  t.deepEqual(output.name, 'world')
+})
 
-test("VariableDeclaration-define global var in block scope", t => {
-  const scope = new Scope();
+test('VariableDeclaration-define global var in block scope', t => {
+  const scope = new Scope()
 
   const func = customEval(
     `
@@ -109,14 +109,14 @@ function run(){
 
 module.exports = run;
       `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(func(), "world");
-});
+  t.deepEqual(func(), 'world')
+})
 
-test("VariableDeclaration-redefine global var in block scope", t => {
-  const scope = new Scope();
+test('VariableDeclaration-redefine global var in block scope', t => {
+  const scope = new Scope()
 
   const func = customEval(
     `
@@ -128,14 +128,14 @@ function run(){
 
 module.exports = run;
       `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(func(), "hello");
-});
+  t.deepEqual(func(), 'hello')
+})
 
-test("VariableDeclaration-continuous-define continuous assignment", t => {
-  const scope = new Scope();
+test('VariableDeclaration-continuous-define continuous assignment', t => {
+  const scope = new Scope()
 
   const { a, b } = customEval(
     `
@@ -144,10 +144,10 @@ var b = a;
 a.x = a = {n: 1};
 module.exports = {a, b};
       `,
-    scope
-  );
+    scope,
+  )
 
-  t.deepEqual(a.n, 1);
-  t.deepEqual(b.n, 2);
-  t.deepEqual(b.x, a);
-});
+  t.deepEqual(a.n, 1)
+  t.deepEqual(b.n, 2)
+  t.deepEqual(b.x, a)
+})
diff --git a/final/test/while/scope.test.js b/final/test/while/scope.test.js
index dc71fa6..534a0c4 100644
--- a/final/test/while/scope.test.js
+++ b/final/test/while/scope.test.js
@@ -1,8 +1,8 @@
-const test = require('ava');
-const { customEval, Scope } = require('../../eval');
+const test = require('ava')
+const { customEval, Scope } = require('../../eval')
 
-test("var in while block should cover the parent scope", t => {
-  const scope = new Scope();
+test('var in while block should cover the parent scope', t => {
+  const scope = new Scope()
 
   const a = customEval(
     `
@@ -14,13 +14,13 @@ while(true){
 
 module.exports = a;
   `,
-    scope
-  );
-  t.deepEqual(a, 2);
-});
+    scope,
+  )
+  t.deepEqual(a, 2)
+})
 
 test("let in for-in block should define in it's scope", t => {
-  const scope = new Scope();
+  const scope = new Scope()
 
   const obj = customEval(
     `
@@ -35,14 +35,14 @@ while(true){
 
 module.exports = {a: a, b: b};
   `,
-    scope
-  );
-  t.deepEqual(obj.a, 1);
-  t.deepEqual(obj.b, 2);
-});
+    scope,
+  )
+  t.deepEqual(obj.a, 1)
+  t.deepEqual(obj.b, 2)
+})
 
 test("const in for-in block should define in it's scope", t => {
-  const scope = new Scope();
+  const scope = new Scope()
 
   const obj = customEval(
     `
@@ -57,16 +57,16 @@ while(true){
 
 module.exports = {a: a, b: b};
   `,
-    scope
-  );
-  t.deepEqual(obj.a, 1);
-  t.deepEqual(obj.b, 2);
-});
+    scope,
+  )
+  t.deepEqual(obj.a, 1)
+  t.deepEqual(obj.b, 2)
+})
 
-test("var in for-in block and parent scope const some name var", t => {
-  const scope = new Scope();
+test('var in for-in block and parent scope const some name var', t => {
+  const scope = new Scope()
 
-  t.throws(function() {
+  t.throws(function () {
     customEval(
       `
 let a = 1;  // define let var
@@ -76,7 +76,7 @@ while(true){
   break;
 }
     `,
-      scope
-    );
-  });
-});
+      scope,
+    )
+  })
+})