Fixed not copying middleware array and just using this, also more tests for it

Author: idchlife

index.js

@@ -78,10 +78,14 @@ const botCallback = function botCallback() {
    * is function, then callback for bot message is added
    */
   if (args.length && typeof args[0] === 'function') {
-    this.middlewares.push(args[0]);
+    const copy = {
+      middlewares: this.middlewares.slice()
+    };
 
-    const callback = botCallback.bind(this);
-    callback.use = use.bind(this);
+    copy.middlewares.push(args[0]);
+
+    const callback = botCallback.bind(copy);
+    callback.use = use.bind(copy);
 
     return callback;
   }

tests.js

@@ -84,7 +84,7 @@ describe('basic middleware usage', () => {
     expect(v.join('')).to.equal('ABCD');
   });
 
-  it('should properly throw errors and also pass it to middleware error handler', function *() {
+  it('should properly throw errors and also pass it to middleware error handler', function* () {
     let wasThereError = false;
     let middlewareErrorHandlerWorked = false;
 
@@ -111,4 +111,33 @@ describe('basic middleware usage', () => {
       expect(middlewareErrorHandlerWorked).to.equal(true);
     }
   });
+
+  it('should properly pass copied context and not affect previous middlewares', function* () {
+    const values = [];
+
+    const def = use(() => {
+      values.push('Z');
+    });
+
+    const a = def.use(() => {
+      values.push('A');
+    });
+
+    const b = def.use(() => {
+      values.push('B');
+    });
+
+    const c = b.use(() => {
+      values.push('C');
+    });
+
+    yield a(botArgumentsMock);
+    yield b(botArgumentsMock);
+
+    expect(values.join('')).to.equal('ZAZB');
+
+    yield c(botArgumentsMock);
+
+    expect(values.join('')).to.equal('ZAZBZBC');
+  });
 });