Describe test design techniques like: State-transition diagrams, Decision tables, Activity diagrams.

The testing of the software systems or applications apart from the human labor is aided by a variety of testing techniques. In this article we are going to discuss about three of such software testing techniques mentioned below:

1. State transition diagrams,
2. Decision tables and
3. Activity diagrams.

1. Test Design Technique - State transition diagrams 

- These are some kind of diagrams that give a detailed description of the behavior of the software systems and applications. 

- The basic condition for the state transition diagrams is that the description of the software system or application should be composed of a particular number of states and employ a reasonable abstraction.

- There are various forms of state diagrams and all of them differ with each other in respect of their semantics. 

- However, the description provided by the state diagrams is quite concise and represents only an abstract view.

- The behavior of the software system or application is first analyzed and represented in series of events that could take place in one or more possible states. 

- Each diagram provides a visual representation of the objects belonging to a particular class and the different states of the objects spread through out the software system or application can be tracked. 

- Also, the finite state machines can be represented graphically by the state transition diagrams. - The use of state diagrams under the concept of finite machines was introduced by C.E. Shannon and W. Weaver. 

“Directed form” is the most classic form of the state transition diagrams for a finite automation (FA) or finite state machine. It consists of the following elements:

      (i) Vertices: a finite set of states which are represented by circles bearing a unique designator   label.

        (ii) Input symbols: a finite collection of input designators.

        (iii) Output symbols: a finite collection of output designators.

        (iv) Edges: meant to represent the state transitions.

        (v) Start state

        (vi) Accepting state

2. Test Design Technique : Decision Tables

- This test design technique represents a compact way to model complicated logic by associating the conditions with the actions that have to be performed. 

- The decision tables consists of 4 quadrants as stated below:

         (i) Conditions

         (ii) Condition alternatives

         (iii) Actions

         (iv) Action entries

- Each decision in a decision table corresponds to a variable, predicate and relation whose possible values are stated in a list among the condition alternatives. 

- Each action is equivalent to procedures or operations that are to be performed. 

- The actions to be performed are specified by the entries made. 

- The decision tables are known to vary widely according to the way in which the conditions alter and also according to the representation of the action entries.

- Most of the decision tables make use of the simple true or false values that are used to represent the alternatives to the conditions stated in it. 

3. Test Design Technique : Activity Diagrams

- This is another graphical aid that represents the work flows of step wise actions and activities along with aspects like choice, concurrency and iteration. 

- Usually these diagrams make use of the unified modelling language to provide a description of the operational and business step by step work flows of the components of a software system or application. 

It constitutes of some basic shapes like:

(i)  Diamonds: represent decisions.

(ii) Black circles: represent the start of the activity.

(iii)Encircled black circles: represent the end of the activity.

(iv)Rounded rectangles: represent activities.

(v) Bars: represent start (split) or end (join) of the activities that are concurrent. 

Explain the concepts of syntax test technique?

Very few people are familiar with the term syntax test technique. We shall discuss about this testing technique but after a brief discussion about the syntax of the programming languages.

Every real world language in this world has got certain rules following which the meaningful statements and sentences can be drafted from the raw words. These rules are collectively known as the syntax of the language. Similarly syntax also exists for the computer programming languages.

About Syntax and Syntax Test Technique

- Each programming language has got its own unique syntax.

- The syntax is known to define the surface of a language.

- Type of syntax of a language depends on the type of the programming i.e., whether it is a text based language or a visual based language.

- Syntax forms a part of the semantics.

- The syntax test technique involves the process of parsing i.e., the linear sequence of the tokens is transformed in to a hierarchical syntax tree.

- Parsing is also an effort and time consuming process but, nowadays several automated tools are available for this purpose also and are quite effective in generating parses.

- These parses are generated using the language grammar specifications as stated in the Backus- Naur form.

- Backus- Naur forms as well as regular expressions of the lexicon together comprise the syntax of the textual programming languages.

- There are other rules called productions which are used to classify the syntax in to different categories.

- The syntax just describes whether or not the program is valid.

- It is the semantics which describe the meaning of the program.

- It is not necessary that a syntactically correct code of the program should be semantically correct also.

Steps of Syntax Test Technique

A typical syntax testing technique consists of the following steps:

1. Identification of the format of the target language.

2. Definition of the syntax of the target language in to formal notation like Backus- Naur form.

3. Testing the syntax under normal conditions by keeping the Backus- Naur form of the language under adequate coverage. This is the minimal requirement for carrying out a syntax test.

4. Testing of the garbage conditions i.e., testing the software system against the invalid input test data. This condition has a high pay off and automation is highly recommended.

5. Debugging of the whole software program.

6. Automation of the test execution process. This is necessary since a lot of test cases are required for the effective syntax testing.

7. For carrying out the whole process, 3 most frequent wrong actions have been identified as shown below:

(a) The recognizer could not identify the string which was good.
(b) The recognizer accepted a bed string.
(c) The recognizer crashed or hanged during the process of the recognition of the good and bad strings.
(d) Any incorrectness in the Backus- Naur specifications can spoil a good string and turn it in to a bad one.

8. There should be a proper testing strategy since all the strings cannot be tested.

9. Only one error should be generated and tested each time.

10. First, all the single errors should be tested using specifically created test cases, then the double errors and lastly the triple errors are tested.

11. Your focus should be on one level at a time.

Dangers related to Syntax Testing

Certain dangers have also been identified related to the syntax testing:

(a) It is quite common for the testers to forget the normal cases.

(b) While testing, testers often go overboard with the testing combinations.

(c) Syntax testing is often taken very lightly since it is pretty easy when compared to the structural testing.

(d) A lack of knowledge about the program can make you to execute many test cases. So its better to have a thorough study of the program before you test it.

What are different HTML errors?

HTML or hyper text mark up language is perhaps one of the most used mark up languages for the web pages, sites and applications with which most of us are familiar. This language is written using the HTML elements which mainly constitute of the tags enclosed in the angle brackets like:

These elements are housed in the web page or site. Most of the HTML tags are implemented in pairs of two.

HTML ELEMENTS AND CONTENT
- Some tags are even empty and are commonly known as empty elements.
- These are usually unpaired unlike the filled elements which are paired.
- In the paired tags, the first tag is called the start tag and the second one is then called the end tag.
- Between these two tags, any text, comments, tags etc can be added by the designer of the web sites.
- The content that is to be added should only be of textual type.
- Due to some wrong designing principles often some errors are introduced in to the html of the web site or the page.
- One of the most common errors is the insertion of the graphical content in to the html.
- Such content is neither displayed nor is it interpreted.
- It simply causes the malfunctioning of the web site.
- Other elements of the html allow the addition of the graphical content and only these should be used whenever some graphics are to be inserted in to the page.
- Html elements provide a means for the creation of the structured documents that denote the structural semantics for textual content like:

1. Lists
2. Links
3. Paragraphs
4. Headings
5. Quotes and so on.

DIFFERENT HTML ERRORS AND THEIR IMPACT

- Html can also be embedded in to the scripts like javascript which also some times leads to errors when inserted incorrectly.
- Such errors affect the behaviour of the web sites and cause them to behave abnormally.
- Whenever the site is affected by an error or a bug is encountered, a set of error messages is generated by the business logic component which is then stored as a string in any of the available scopes.
- For using such functions, you need to define an application scope with the name of default attribute, because if such a scope is not found, then nothing is to be rendered by the business logic.
- Some designers forget to define such scopes and therefore end up with unnecessary errors in their web sites.
- Many more errors occur whenever a requested is generated by the client to the web server.
- In such cases the server responds with some status messages, few of which have been mentioned below along with the possible errors:

1. 400:
Bad syntax of the request is preventing the server to process it.

2. 401:
The request though being cannot be processed because of unavailability of the authentication processes.

3. 404 not found:
The page requested by the client is found to be unavailable at that moment.

4. 405 method not allowed:
The client made request in such a way that is not supported by that site.

5. 407 proxy authentication required:
The client has not authenticated its proxy.

6. 408 request time out:
The server’s request time expired while waiting for the client to generate one.

7. 409 conflict:
The server is not able to process the request because of the presence of some conflict in it.

8. 410 gone:
The page that was requested is no longer available on the web.

How to assess alternative architectural designs?

There are many architectural alternatives that need to be assessed. There are different ways to assess the design:

Trade off Analysis Method
It establishes an iterative evaluation process for software architectures. It involves six steps:
- All the scenarios are collected.
- Requirements, constraints and environment description are elicited.
- Architectural styles or patterns chosen to address scenarios and requirements are described.
- Quality attributes are evaluated.
- The sensitivity of quality attributes to architectural attributes are identified.
- Critique candidate architectures using sensitivity analysis.

Architectural Complexity
In architectural complexity, the dependencies between the components are assessed within the architecture. Dependencies can be divided into:
- Sharing dependencies represent dependence relationship among consumers or producers.
- Flow dependencies represent dependence relationships between producers and consumers of resources.
- Constrained dependencies represent constraints on the flow of control among set of activities.

Architectural Description Languages
Architectural description language provides a semantic and syntax for describing a software architecture. It is a set of tools and notation that allows the design to be represented in an unambiguous and understandable fashion.

User Interface Analysis and Design - Interface analysis and design models

User interface design begins with creating of different models of system function, human and computer tasks required to achieve system function are delineated, design issues applying to interface designs are considered, tools that are used and result that is evaluated by end-users for quality.

Analyzing and designing a user interface design requires four different models:
User Model
It is established by human or software engineer. It establishes the profile of end users of system. Users are categorized as:
- Novices: No syntactic and little semantic knowledge.
- Knowledgeable, intermittent users: Reasonable semantic and low recall or syntactic knowledge.
- Knowledgeable, frequent users: Good semantic and syntactic knowledge.

Design Model
Software engineer creates a design model. It includes data architectural, interface and procedural representations of the software.

User's Mental Model
It is created by end-user. It is the image of the system that end users carry in their mind. Accuracy of the description depends on the user's profile.

Implementation Model
It is created by implementers of the system. It combines the outward manifestation of computer based systems coupled with all information that describe system syntax and semantics.

When the implementation and user's mental model are coincident, users are comfortable with the software and use it effectively.

User Interface Testing - Interface testing strategy

The user interface model is reviewed to ensure that it conforms to customer requirements and to other elements of analysis model. During testing, focus is shifted towards application specific aspects of user interaction as they are manifested by interface syntax and semantics.

The goal of interface testing is to:
- uncover errors related to specific interface mechanism.
- uncover errors in the way interface implements semantics of navigation, web application functionality or content display.

Objectives that should be achieved are:
- Interface features are tested to ensure that design rules, aesthetics, and related visual content are available for user without error.
- Individual interface mechanisms are tested in a manner that is analogous to unit testing.
- Each interface mechanism is tested within the context of a use case or navigation semantic units for a specific user category.
- The complete interface is tested against selected use cases and navigation semantic units to uncover errors in the semantics of the interface.
- The interface is tested within a variety of environments to ensure that it will be compatible.

Usability testing evaluates the degree to which users can interact effectively with the web application and the degree to which the web application guides user actions, provides meaningful feedback, and enforces a consistent interaction approach. Usability tests are designed by a web engineering team, but the tests themselves are conducted by end users.

Steps to be followed are :
- define a set of usability testing categories and identify goals for each.
- design tests that will enable each goal to be evaluated.

Introduction to Navigation Design - Navigation Semantics and Syntax

Once the web application architecture and the content is defined, navigation pathways that enable users to access the web application content and functions.
- semantics of the navigation for different users of the site should be identified.
- syntax of achieving the navigation should be defined.

NAVIGATION SEMANTICS

Each user category has a user hierarchy and related use cases. There are different navigation requirements for each actor. A set of classes are defined for the use cases developed for each user. It contains one or more content objects or web application functions. As interaction with web application occurs, series of Navigation Semantic Units(NSUs) are encountered. A NSU describes the navigation requirements for each use case. The NSU shows how an actor moves between content objects or web application functions.
Navigation Semantic Unit is a set of information and related navigation structures that collaborate in the fulfillment of a subset of related user requirements.

The Web application designer creates a navigation semantic unit for each use case associated with each user role. During initial stages of navigation design, the web application content architecture is assessed to determine one or more ways of navigating for each use case. Ways of navigating identifies navigation nodes and the links that enable navigation between them.

NAVIGATION SYNTAX

The syntax of navigation design are:
- Tabs: a variation of navigation bar or column.
- Individual navigation link: test based links, icons, buttons and graphical metaphors.
- Horizontal Navigation bar: lists major content or functional categories in a bar containing appropriate links.
- Vertical Navigation column: lists major content or functional categories and second lists virtually all major content objects within web application.
- Site maps: provide an all-inclusive table of contents for navigation to all content objects and functionality contained within web application.