• A web application is an application that users access through a web browser over the Internet or an intranet
• A web application is a system that usually includes a set of scripts located on a web server and interacting with databases and other sources of dynamic content
• We will call web applications any applications that provide a web interface

• A web browser is used to interact with the user. The user does not talk to the server directly
• The server and the browser communicate by sending each other requests over a standard protocol (HTTP/HTTPS)
• Only the web browser can initiate a connection
• Interaction with the user is usually carried out through form elements and submitted requests, most often GET or POST
• These stages are separated by clearly identifiable requests from the browser to the application
• A standard representation (HTML / XHTML) is used to describe the interface

1. The user clicks a link, the browser sends a request to the server and waits for the response: Browser -> Server

2. The server runs a script, sends the result to the browser and finishes its work: Server -> Browser

3. The browser displays the page, “scanning” it for links that must be requested from the server (the <img src>, <script src> tags and so on) and sends the corresponding requests: Browser -> Server, Browser -> Server...

4. The user fills in a form and clicks a button: Browser -> Server

5. The server processes the form, writes the data to the database and sends the browser a Location header: Server -> Browser

6. The browser, having received this header, requests the specified page: Browser -> Server

7. The server handles the request... and so on

• By the time the user sees the page in front of them and starts doing something with it, the Server has already finished its work!
• And the user is interacting not with the Server but with their own HTML page, which they received in the browser
• In most cases the result of a script running on the Server is plain text: the text of an HTML page, which is handed to the browser and displayed by it as ordinary HTML
• The client asked — the server delivered.
• This makes the answer clear to the question of whether you can find out exactly how many users are on a site right now. You can't. Because there is nobody “on the site”. They connect, request a page and disconnect.

Client-server is a network architecture in which devices are either clients or servers

• The client is the machine that makes a request, and the server is the machine that responds to it
• Both terms (client and server) can be applied to physical devices as well as to software
• When testing, it is helpful to picture the configuration of the system the web application under test runs in, so that you can look into problems more effectively
• Understanding the system configuration makes your bug descriptions more valuable

How Flex differs from Flash, and the advantages of Flex:

• Flex extends the basic capabilities of Flash by letting you describe the application interface in XML, which speeds up and simplifies the development of rich web applications
• Flex components for building charts are designed to be easy to use. Example: Google Analytics charts
• Flex 2, besides development speed, provides the full multimedia capabilities of the Flash Platform, including streaming video and audio, and supports pushing data to clients
• AJAX can work with Flex

JavaScript:

• A programming language interpreted by web browsers: scripting-language code such as typeScript and JavaScript embedded in an HTML page, capable of running Java applets and controls
• Originally used mostly to script the behavior of the
  browser, it has since evolved and now powers full-fledged programs, on both the client side and the server side

An example of drawing a 3D space with JS http://maxogden.github.io/voxel-perlin-terrain/

ActiveX:

• This is code interpreted by the browser and executed in its own address space
• A web page can contain references to ActiveX controls, which are dynamically loaded libraries that run in the browser's address space
• Moreover, unlike Java applets, the execution of ActiveX controls is in general not subject to any restrictions on access to files and other resources of the operating system and the network

Outdated and rarely used

CGI (Common Gateway Interface) - a common gateway interface used to connect an external program to an application's web server. These are usually console applications that generate HTML code, which is passed to the browser. How it works:

• They are called by specifying their name (and parameters) in the URL
• It is important that web clients do not have to be browsers; they can be
  any programs that use the HTTP protocol
• The input is the content of the HTTP header or the request body,
  depending on the protocol used
• They can be code in scripting languages or an executable file
  that can be created with almost any development tool

Servlet

• A servlet is a CGI program written in Java, with better performance and the ability to keep state (sessions)
• A servlet is a program that extends the functionality of a web server by dynamically generating content and interacting with web clients using the request-response model
• Servlets are supported automatically by most web servers
• Servlets have become widespread in implementing web services

Web applications based on libraries :

for example, ISAPI or DSO

The problem of limited web application performance can be solved by building the application as libraries loaded into the web server's address space

Placing code executed by the web server inside a web page:

• ASP.NET technology: the ability to handle on the server the events that occur in the client application. ASP.NET is part of the .NET Framework and therefore gives access to all the capabilities of that platform
• JSP (Java Server Pages) technology: Java code (a servlet) is compiled once, on the first request to it, its methods are executed, and the results of those methods are placed into a data set sent to the browser
• PHP (Personal Home Pages) technology: the use of CGI applications that interpret scripting-language code embedded in an HTML page. It is easy to develop with and available for various platforms (more on this later)

When the value of an attribute of a particular environment does not stay constant during a procedure, the operating environment becomes dynamic

The web environment can rightfully be classed as a dynamic environment

Variable parameters of a dynamic web environment:

Resource-specific:

1. Available RAM
2. Disk space in use

Timing-specific:

1. Network latency
2. The order in which user transactions are performed

When a test case depends on exactly reproducing both a set of actions and the operating environment, and the environment cannot be reproduced (given its dynamic nature), the bug becomes irreproducible or hard to reproduce

The HTML markup language (HyperText Markup Language) is a publishing language used in the web environment, the WWW (World Wide Web)

HTML is not a programming language in the broad sense: you cannot build a full-fledged application with it

HTML gives authors the means to:

• Publish electronic documents with headings, text, tables,
  lists, photos, etc.
• Retrieve electronic information with a mouse click on a
  hypertext link
• Design forms for carrying out transactions with remote services,
  for use in searching for information, making reservations, ordering
  products, etc.
• Embed spreadsheets, video clips, sound clips and
  other applications directly into documents

If the HTML topic interests you, or you need deeper knowledge for the place where you plan to work: the HTML reference and the HTML tutorial are here to help

Other languages in the web environment

DHTML (Dynamic HyperText Markup Language) is an extension of HTML that lets you create web pages with interactive elements such as:

• a moving background beneath the static content of the document
• moving objects, drop-down menus, buttons that light up
  when the mouse cursor hovers over them, animation, scrolling marquees, etc.

JavaScript is a language for writing programs executed by the browser. It is the standard for Dynamic HTML. For security reasons, it cannot affect anything except the browser. It has no means of accessing the computer's disk, except for writing cookies

• JavaScript significantly extends the capabilities of a document created in this format
• A module written in JavaScript is integrated into an HTML file as a subroutine
• It is called for execution from the corresponding line of HTML code with a standard command. It can also exist as a separate file

PHP is a programming language designed specifically for building server-side applications

It has become very widespread thanks to its rich capabilities and ease of use

Since PHP is one of the most widespread languages for building and managing websites, this article examines in detail how this server-side web language works. Consider it extracurricular reading :')

In fact, the HTTP protocol offers only a few ways to communicate.

A browser can send information to a server in the following ways:

• GET - data is passed in the address bar, for example when the user clicks a link
• POST - when the user clicks a button in a form
• Cookie - if the server has set a cookie and it has not expired, the browser sends it with every request to the server
• HTTP authentication - if the server has requested HTTP authorization, the browser sends the entered login and password with every request

LINK

Associates header information with a document on the server

UNLINK

Removes the association between header information and a document on the server

PUT

Places the body of the request at the specified URI

DELETE

Deletes the data located on the server at the given URI

OPTIONS

Requests information about the server's communication options.

To request data about the server as a whole, instead of the URI

of the request, use the * character

TRACE

Requires the body of the request to be returned
unchanged. Used for debugging

Rules for working with cookies

If a cookie takes a new value while the browser already holds a cookie with the same NAME, domain and path, the old value is replaced by the new one. In all other cases new cookies are added.

Using expires does not guarantee that a cookie will be kept for the specified period of time, since the client (browser) may delete the entry because of a lack of allocated space or some other limits.

The client (browser) has the following limits:

• up to 300 cookie values can be stored in total
• each cookie cannot exceed 4 KB
• up to 20 cookie values can be stored per server or domain

Classification of requirements for web applications:

• Functional: define the functionality of the system that lets

users accomplish their tasks within their business processes

• Non-functional: describe the characteristics of the application that matter to the user when working with the system:

1. Application reliability requirements
2. Application performance requirements
3. Security requirements
4. Scalability requirements

• As non-functional requirements for web applications, one can

consider the web standard of the W3C, the World Wide Web Consortium:

http://www.w3.org/standards/

An application/site built to web standards means following the standards (HTML, XHTML, XML, CSS, XSLT, DOM, MathML, SVG, etc.) and proven best practices:

• valid code
• accessible code
• semantically correct code
• friendly URLs

For example, http://www.qaacademy.net/#!level9/g7m0g, is not a friendly URL at all; a friendly one would be http://www.qaacademy.net/level9

In other words, an application/site built to standards should ideally be:

• Well structured. The whole HTML document should have a clear hierarchy, and every logical block should be wrapped in div tags
• Clean (with valid code). While working with a site you must keep checking the console: errors thrown to the console are failures in the program, and therefore bugs
• CSS-based. All parameters of color, font, spacing and so on should be described in the component's style
• Search-engine friendly (SEO). SEO is a separate big topic that has nothing to do with testing. But we are interested only in its functional aspects. As testers, we check whether the version of the site for robots (the SEO version) opens when the parameter ?_escaped_fragment_= is added to the URL. The SEO version has no styles, is not meant for users and contains only the site's key search phrases and images Is there a sitemap for the search engine to index the site? Is there a robots.txt file that tells search bots how to index the site?

Below are recommendations for testing web applications using the web standards checklist method