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Basic but proper use of beforeEach() or afterEach() with mocha.js and chai.js [duplicate]

This question already has answers here:
How does variable scope work within the Mocha test framework?
(2 answers)
Closed 6 years ago.
I want to use mocha/chai to test code related to binary search trees. Here, I am testing the public insert method. I want to use beforeEach() and/or afterEach() hooks to reset the test environment prior to each it() statement so that I don't have to completely repeat the basics. However, I keep getting various errors.
Spec
describe("BinarySearchTree insert function", function() {
beforeEach(function() {
var binarySearchTree = new BinarySearchTree();
binarySearchTree.insert(5);
});
it("creates a root node with value equal to the first inserted value", function () {
expect(binarySearchTree.root.value).to.equal(5);
});
it("has a size equal to the amount of inserted values", function () {
binarySearchTree.insert(3);
expect(binarySearchTree.size).to.equal(2);
});
it("returns an error for non-unique values", function () {
binarySearchTree.insert(3);
expect(binarySearchTree.insert(3)).to.throw(String);
});
it("if inserted value is larger than current node, make or descend to rightChild", function () {
binarySearchTree.insert(3);
binarySearchTree.insert(10);
binarySearchTree.insert(7);
expect(binarySearchTree.root.rightChild.value).to.equal(10);
});
});
Error: ReferenceError: binarySearchTree is not defined
In truth, I expected errors before there is no afterEach() resetting the test environment, not because binarySearchTree is not defined. I'd like to accomplish this, if at all possible, with only Mocha and Chai (and not other packages like Sinon, etc).
Tested Code
exports.Node = Node;
function Node(value) {
this.value = value;
this.leftChild = null;
this.rightChild = null;
}
exports.BinarySearchTree = BinarySearchTree;
function BinarySearchTree() {
this.root = null;
this.size = 0;
}
BinarySearchTree.prototype.insert = function(value) {
// 1) when root node is already instantiated
if (this.root === null) {
// tree is empty
this.root = new Node(value);
this.size++;
} else {
// 2) nodes are already inserted
var findAndInsert = function (currentNode) {
if (value === currentNode.value) {
throw new Error('must be a unique value');
}
// base case
if (value > currentNode.value) {
// belongs in rightChild
if (currentNode.rightChild === null) {
currentNode.rightChild = new Node(value);
} else {
findAndInsert(currentNode.rightChild);
}
} else if (value < currentNode.value) {
// belongs in leftChild
if (currentNode.leftChild === null) {
currentNode.leftChild = new Node(value);
} else {
findAndInsert(currentNode.leftChild);
}
}
};
findAndInsert(this.root);
this.size++;
}
};
Bonus question... I'm not sure if I am properly testing for the thrown error (when a non-unique value is inserted)?

It is undefined because it is not in test function scope. Define it one step before in describe scope. For reference, look at the Angular docs. https://docs.angularjs.org/guide/unit-testing
describe("BinarySearchTree insert function", function() {
var binarySearchTree;
beforeEach(function() {
binarySearchTree = new BinarySearchTree();
binarySearchTree.insert(5);
});
it("creates a root node with value equal to the first inserted value", function () {
expect(binarySearchTree.root.value).to.equal(5);
});
it("has a size equal to the amount of inserted values", function () {
binarySearchTree.insert(3);
expect(binarySearchTree.size).to.equal(2);
});
it("returns an error for non-unique values", function () {
binarySearchTree.insert(3);
expect(binarySearchTree.insert(3)).to.throw(String);
});
it("if inserted value is larger than current node, make or descend to rightChild", function () {
binarySearchTree.insert(3);
binarySearchTree.insert(10);
binarySearchTree.insert(7);
expect(binarySearchTree.root.rightChild.value).to.equal(10);
});
});

The reason you are getting binarySearchTree is undefined is explained already.
I would like to talk about beforeEach and afterEach functions.
In beforeEach function we generally do basic setup for test things like variables initialization, stubbing out external calls etc.
and 'afterEach' method works like destroy functions where generally we write memory releases stuff.

Array of functions in javascript

I have some JavaScript functions in each page that I call them after jQuery is loaded.
The function in Questions.aspx page is afterQuestions(), the function in Default.aspx is afterDefault() and so on ....
In my master page I am calling them like:
if(typeof(afterQuestion) == 'function') afterQuestions();
if(typeof(afterDefault) == 'function') afterDefault();
As the number of functions grew, I tried something like:
var _fs = [After, AfterDefault, afterSettings, afterQuestions];
for (var i = 0; i < _fs.length; i++) if (typeof (_fs[i]) == "function") _fs[i]();
But it doesn't work this way. Can you please help me how can I create an Array of functions and call them?
Edit: I think nobody had read the question well to see that the all functions won't exist at the same time and that was the problem creating the array. I solved it by adding created functions to a global array and the looping and excuting functions in that array

If the function is not defined, you will get a JavaScript error since you are trying to reference a variable that is not defined. The type of check in your original code gets around that issue.
Your best bet is to namespace the functions into an object and use dot notation.
var methods = {
After : function () {console.log("After"); },
AfterDefault : function () {console.log("AfterDefault"); },
afterSettings : function () {console.log("afterSettings"); }
};
var _fs = [methods.After, methods.AfterDefault, methods.afterSettings, methods.afterQuestions];
for (var i = 0; i < _fs.length; i++) {
if (typeof (_fs[i]) == "function") {
_fs[i]();
}
}
Now when you want to register the methods you can just add to the methods object.
methods = methods || {};
methods.afterSettings = function () { console.log("added this in"); };
Now if the method is not defined the namespace will return undefined and the check will not error out.

Chromium Embedded how to execute a javascript callback from c++?

Recently I have been trying to bind my application to CEF, the process was slow but I made some progress over the last days. However there is one thing I just can't get to work.
What I want to achieve is:
1. Registering a callback function within Javascript (These functions will be called when an event happens in my application)
2. Save the callback.
3. When the event occurs, execute the registered callback.
Now I got step 1 and 2 to work, but step 3 is where the problem is.
I tested it first by registering a callback and then calling it with an executeCallback() function in Javascript and it worked. But whenever I try to execute the callback from within C++ it doesn't work.
I create the setEventCallback in the onContextCread()
CefRefPtr<CefV8Value> object = context->GetGlobal();
CefRefPtr<CefV8Value> simplixObj = CefV8Value::CreateObject(NULL);
object->SetValue("simplix", simplixObj, V8_PROPERTY_ATTRIBUTE_NONE);
func = CefV8Value::CreateFunction("setEventCallback", $simplixHandler);
simplixObj->SetValue("setEventCallback", func, V8_PROPERTY_ATTRIBUTE_NONE);
With $simplixHandler being an instance of my own handler.
Here is the setEventCallback in my handler:
bool SimplixHandler::setEventCallback(CefRefPtr<CefV8Value> object, const CefV8ValueList& arguments, CefRefPtr<CefV8Value>& retval, CefString& exception)
if (arguments.size() == 2 && arguments[0]->IsString() && arguments[1]->IsFunction()) {
//Get name of callback
std::string callbackName = arguments[0]->GetStringValue();
//Get the current context
CefRefPtr<CefV8Context> context = CefV8Context::GetCurrentContext();
//Insert into callbacks
$callbacks[callbackName] = std::make_pair(context, arguments[1]);
return true;
}
else if(arguments.size() != 2) {
exception = CefString("Invalid amount of parameters. Expected 2, received " + arguments.size());
return false;
}
else {
exception = CefString("Incompatible parameter types, expected (string, function).");
return false;
}
I then try to execute the callbacks by calling executeCallback:
bool SimplixHandler::executeCallback(std::string name, CefRefPtr<CefListValue> list) {
bool handled = false;
if (!$callbacks.empty() && $callbacks.count(name) != 0) {
std::pair<CefRefPtr<CefV8Context>, CefRefPtr<CefV8Value>> pair = $callbacks[name];
CefRefPtr<CefV8Context> context = pair.first;
CefRefPtr<CefV8Value> func = pair.second;
context->Enter();
CefV8ValueList callArgs;
//First argument is function name
CefRefPtr<CefV8Value> args = CefV8Value::CreateArray(list->GetSize());
setList(list, args);
callArgs.push_back(args);
CefRefPtr<CefV8Value> retval = func->ExecuteFunction(NULL, callArgs);
if (retval.get()) {
if (retval->IsBool())
handled = retval->GetBoolValue();
}
context->Exit();
}
return handled;
}
I call this function from within my SimplixHandler, however I call callbacks by calling the specific event function, example:
bool SimplixHandler::notifyDirectoryChanged(std::string directory) {
CefRefPtr<CefListValue> list = CefListValue::Create();
list->SetSize(1);
list->SetString(0, directory);
return executeCallback("onDirectoryChange", list);
}
And finally my Javascript:
function dirChange(dir) {
document.getElementById("filename").innerHTML = "It's something";
}
simplix.setEventCallback("onDirectoryChange", dirChange);
I know the event gets called (because I first had nullpointer exception due to wrong linking of classes, that's fixed now), but the Javascript Callback does not get called.
Does anyone know what I am doing wrong?
Thanks in advance.

you can use any function in html code for callback.
Renderer:
bool SimpleApp::OnProcessMessageReceived(CefRefPtr<CefBrowser> browser,
CefProcessId source_process,
CefRefPtr<CefProcessMessage> message)
{
std::string message_name = message->GetName();
if( message_name == "FUNC")
{
//AfxMessageBox("stop");
//browser->GetMainFrame()->ExecuteJavaScript("super_test('works!');", browser->GetMainFrame()->->GetURL(), 0);
CefRefPtr<CefV8Value> object = m_context->GetGlobal();
CefRefPtr<CefV8Context> v8context = browser->GetMainFrame()->GetV8Context();
v8context->Enter();
CefRefPtr<CefV8Value> func_test = object->GetValue("super_test");
if(func_test == NULL)
{
v8context->Exit();
return false;
}
CefV8ValueList arguments;
CefRefPtr<CefV8Value> test = CefV8Value::CreateString("hello from c++");
arguments.push_back(test);
CefRefPtr<CefV8Value> retval = func_test->ExecuteFunction(NULL, arguments);
v8context->Exit();
return true;
}
return false;
}
jScript:
<script>
function super_test(resp)
{
alert(resp);
return "7777";
}
browser:
CefRefPtr<CefProcessMessage> message = CefProcessMessage::Create("FUNC");
SimpleHandler::GetInstance()->GetBrowser()->SendProcessMessage(PID_RENDERER, message);

Is there a way to inject a try catch inside a function?

Maybe some of you know about AOP, in some languages using AOP can lead you to be able to inject code after, before, or while a method is executing,etc.
What I want is to apply the same in Javascript, I am currently working on a massive app which has more than 300 ajax calls, and every time I need to do some change on the catch statement on them, I have to modify them one by one which is very tedious.
What I want to do is something like :
functionName.before("try {")
functionName.after("} catch(ex){
//dostuff
}")
Is it possible? I know there are things like .call, or the arguments object inside every function..which seem pretty meta-function (AOP) functionalities.

Not with before and after, but a wrap will work:
Function.prototype.wrapTry = function(handle) {
var fn = this;
return function() {
try {
return fn.apply(this, arguments);
} catch(e) {
return handle(e);
}
};
};
Then use it like
var safeFunction = functionName.wrapTry(doStuff);

In JavaScript, functions are first-class objects. That means you can manipulate or redeclare them.
Assuming that there is a "foo" function:
var originalFoo = foo;
foo = function()
{
// "before" code.
// Call the original function.
originalFoo.apply(this, arguments);
// "after" code.
};
After that, any call to foo() will call the new function: even with parameters.

Old question but you may take a look over this https://github.com/k1r0s/kaop-ts/blob/master/docs/api.md#available-join-points
import { onException } from "kaop-ts"
import handlingException from "./somewhere"
class Something {
#onException(handlingException)
method() {
// stuff that may throw an error
}
}

I also will give a late answer in order to shed some light onto this special case that every then and now pops up as JavaScript and AOP.
Firstly, cases like the very one presented by the OP always ask for modifying already existing functionality, thus targeting closed code that sometimes is not even owned by the party that sees itself challenged from modifying the control flow of such code.
Why then, not just name it like that ... JavaScript method modification or JavaScript method modifiers.
Secondly, because of already riding the horse of terminology, altering closed functionality in JavaScript has nothing to do with Aspect-oriented Programming unless an implementation that claims to be AO provides abstraction and code-reuse levels for at least Aspect, Advice and Pointcut.
Last, for what the OP is going to achieve and what also has been the accepted answer, there does exist a a whole bunch of before, after around / wrap solutions, almost always unfortunately mentioning AO(P), and in far too many cases not taking care of the context or target which is essential to method modification.
The example I do provide uses a prototypal implementation of afterThrowing. Because JavaScript already features a standardized bind, I'm firmly convinced that Function.prototype is the right place as well for some other method-modifiers
like before, after, around, afterThrowing
and afterFinally.
// OP's example pseudo code
//
// functionName.before("try {")
//
// functionName.after("} catch(ex){
// dostuff
// }")
function doStuffAfterThrowing(exception, originalArguments) {
"use strict";
var context = this;
console.log('context : ', context);
console.log('String(exception) : ', String(exception));
console.log('originalArguments : ', originalArguments);
return "safely handled exception";
}
function doFail() {
throw (new ReferenceError);
}
function oneOutOfManyAjaxCallbacks(payload) {
doFail();
}
var jsonData = {
"foo": "foo",
"bar": "bar"
};
var someModifiedAjaxCallback = oneOutOfManyAjaxCallbacks.afterThrowing(doStuffAfterThrowing, { x: 'y' });
// does fail controlled/handled.
console.log('someModifiedAjaxCallback(jsonData) : ', someModifiedAjaxCallback(jsonData));
// does fail "Uncaught".
console.log('oneOutOfManyAjaxCallbacks(jsonData) : ', oneOutOfManyAjaxCallbacks(jsonData));
.as-console-wrapper { min-height: 100%!important; top: 0; }
<script>
(function (Function) {
var
isFunction = function (type) {
return (
(typeof type == "function")
&& (typeof type.call == "function")
&& (typeof type.apply == "function")
);
},
getSanitizedTarget = function (target) {
return ((target != null) && target) || null;
}
;
Function.prototype.afterThrowing = function (handler, target) { // afterThrowing
target = getSanitizedTarget(target);
var proceed = this ;
return (isFunction(handler) && isFunction(proceed) && function () {
var ret, args = arguments;
try {
ret = proceed.apply(target, args);
} catch (exc) {
ret = handler.call(target, exc, args);
//throw exc;
}
return ret;
}) || proceed;
};
}(Function));
</script>
Having come that far one might also consider reading ...
sandwich pattern in javascript code
Can you alter a Javascript function after declaring it?

In Javascript using try / catch, besides the error message how can I catch function name and all arguments names/values passed?

I'd like to create a generic debugging routine using try / catch, within the catch segment I'd like a piece of code which will log the function name and all params passed (name => value).
Is this possible?
try{
// code
} catch(e) {
var function_name = ''; // how can I get this?
var function_params = ''; // how can I get this?
var errorText = 'UNEXPECTED ERROR: \n\n Error Details: '+e.toString();
errorText = errorText+' Called:'+function_name+'('+function_params+')';
}

In Chrome and Firefox you can use e.stack but no such luck in Internet Explorer.
The stack property is an array that you can loop over. It might differ a bit from browser to browser but it shouldn't be too hard to make a readable stacktrace.
You currently can't catch the arguments in all browsers.
In Chrome you might need to use:
Error.prepareStackTrace = function (error, stack) {
return stack;
}; // augments Chrome's Error.stack property with context data

Try using arguments.callee for the function name
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Functions_and_function_scope/arguments/callee

This isn't an exact answer because I don't give the function Name but this returns the entire function body...
Working sample: http://jsfiddle.net/sS6sY/
Object.prototype.getArgs = function(){
//returns the arguments passed to a function.
var els = [];
for(i=0; i< this.arguments.length; i++){
els.push(this.arguments[i]);
}
return els.join(',')
}
Object.prototype.getMethod = function(){
//returns the function as a string.
return this.constructor;
}
var Foo = function(){
this.arguments = arguments;
try{
throw {
name: 'Oops',
message: 'Didn\'t mean to make a Foo!'
}
}
catch(e){
console.log(this.getArgs());
console.log(this.getMethod());
}
}