Unix Introduction

UNIX is a computer Operating System which is capable of handling activities from multiple users at the same time.UNIX commands can often be grouped together to make even more powerful commands.

Parts of Unix Operating System:

The UNIX operating system comprises three parts: The kernel, the standard utility programs, and the system configuration files.

kernel:

The kernel is the core of the UNIX operating system. Basically, the kernel is a large program that is loaded into memory when the machine is turned on, and it controls the allocation of hardware resources from that point forward.

Standard utility programs

These programs include simple utilities like cp, which copies files, and complex utilities, like the shell that allows you to issue commands to the operating system.

System configuration files:

The system configuration files are read by the kernel, and some of the standard utilities.

Types of UNIX:

There are many different versions of UNIX.
Sun Solaris
GNU/Linux
MacOS X

An UNIX Terminal window will then appear with a % prompt, waiting for you to start entering commands.

UNIX was originally developed at Bell Laboratories as a private research project by a small group of people. Read all about the history of its creation.

we shall use the following typographical conventions:

Characters written in bold typewriter font are commands to be typed into the computer as they stand.

Characters written in italic typewriter font indicate non-specific file or directory names.

Words inserted within square brackets [Ctrl] indicate keys to be pressed.

Don't forget to press the [Enter] key: commands are not sent to the computer until this is done.

The UNIX operating system is made up of three parts; the kernel, the shell and the programs.

The kernel

The kernel of UNIX is the hub of the operating system: it allocates time and memory to programs and handles the filestore and communications in response to system calls.

As an illustration of the way that the shell and the kernel work together, suppose a user types rm myfile (which has the effect of removing the file myfile). The shell searches the filestore for the file containing the program rm, and then requests the kernel, through system calls, to execute the program rm on myfile. When the process rm myfile has finished running, the shell then returns the UNIX prompt % to the user, indicating that it is waiting for further commands.

The shell

The shell acts as an interface between the user and the kernel. When a user logs in, the login program checks the username and password, and then starts another program called the shell. The shell is a command line interpreter (CLI). It interprets the commands the user types in and arranges for them to be carried out. The commands are themselves programs: when they terminate, the shell gives the user another prompt (% on our systems).

Filename Completion - By typing part of the name of a command, filename or directory and pressing the [Tab] key, the tcsh shell will complete the rest of the name automatically. If the shell finds more than one name beginning with those letters you have typed, it will beep, prompting you to type a few more letters before pressing the tab key again.

History - The shell keeps a list of the commands you have typed in. If you need to repeat a command, use the cursor keys to scroll up and down the list or type history for a list of previous commands.

Listing files and directories

ls (list)

When you first login, your current working directory is your home directory.

% ls (short for list)
The ls command lists the contents of your current working directory.

ls does not, in fact, cause all the files in your home directory to be listed, but only those ones whose name does not begin with a dot (.) Files beginning with a dot (.) are known as hidden files and usually contain important program configuration information. They are hidden because you should not change them unless you are very familiar with UNIX!!!

To list all files in your home directory including those whose names begin with a dot, type
% ls -a

mkdir (make directory)

We will now make a subdirectory in your home directory to hold the files you will be creating and using in the course of this tutorial. To make a subdirectory called unixstuff in your current working directory type

% mkdir unixstuff

To see the directory you have just created, type
% ls

Changing to a different directory

cd (change directory)
The command cd directory means change the current working directory to 'directory'. The current working directory may be thought of as the directory you are in, i.e. your current position in the file-system tree.
To change to the directory you have just made, type
% cd unixstuff
Type ls to see the contents (which should be empty)

In UNIX, (.) means the current directory, so typing
% cd .
NOTE: there is a space between cd and the dot
means stay where you are (the unixstuff directory).
This may not seem very useful at first, but using (.) as the name of the current directory will save a lot of typing, as we shall see later in the tutorial.

(..) means the parent of the current directory, so typing
% cd ..

Pathnames
pwd (print working directory)
Pathnames enable you to work out where you are in relation to the whole file-system. For example, to find out the absolute pathname of your home-directory, type cd to get back to your home-directory and then type % pwd

Testing Interview Questions and Answers

Q. What is Agile Testing and how is it different to traditional waterfall or the V model?

Agile Testing is testing practice that follows the principles of agile software development. Agile testing involves all members of an agile team with special skills and expertise to ensure business value is delivered at frequent intervals.

The big difference is that in Agile environment, testing is not a phase, it is an activity parallel to development.

In agile environment, small features of software are delivered frequently, so testing activity should be parallel to development activity. Testing time is short as we are only testing small features.

In the waterfall model, there is a testing phase at the end of the development so, testing is a big effort done after the whole application is developed. Testing time is long as we have to test the whole application.

Q: What is your approach when requirements change continuously?

This question can be asked if you are interviewed for an agile QA position where requirements are likely to change frequently during development. Although a complete change in requirement is possible, most of the time, it is the technical details that are subject to change. e.g. the intent of the requirement or behaviour of the feature is the same but implementation details can change

A: Some possible answers can be:

• Write generic test plans and test cases which focus on the intent of the requirement rather than its exact details
• Work very closely with the product owners or business analysts to understand the scope of change so testing can be updated
• Make sure the team understands the risks involved in changing requirements especially towards the end of sprint
• If you’re going to automate this feature, it is best to wait until the feature is stable and requirements are finalized
• Negotiate to see if the changes can be kept to a minimum and/or implement the changes in next sprint.
• 
  

Can you explain defect age and defect spoilage?

Defect age is also called a phase age or phage. One of the most important things to remember in testing is that the later we find a defect the more it costs to fix it. Defect age and defect spoilage metrics work with the same fundamental, i.e., how late you found the defect. So the first thing we need to define is what is the scale of the defect age according to phases. For instance, the following table defines the scale according to phases. So, for instance, requirement defects, if found in the design phase, have a scale of 1, and the same defect, if propagated until the production phase.
Once the scale is decided now we can find the defect spoilage. Defect spoilage is defects from the previous phase multiplied by the scale. For instance, in the following figure we have found 8 defects in the design phase from which 4 defects are propagated from the requirement phase. So we multiply the 4 defects with the scale defined in the previous table, so we get the value of 4. In the same fashion we calculate for all the phases. That's the spoilage.

Can you explain how the number of production defects is measured?

This is one of the most effective measures. The number of defects found in a production is recorded. The only issue with this measure is it can have latent and masked defects which can give us the wrong value regarding software quality.

Can you explain DRE?

DRE (Defect Removal Efficiency) is a powerful metric used to measure test effectiveness. From this metric we come to know how many bugs we found from the set of bugs which we could have found. The following is the formula for calculating DRE. We need two inputs for calculating this metric: the number of bugs found during development and the number of defects detected at the end user but the success of DRE depends on several factors. The following are some of them:

• Severity and distribution of bugs must be taken into account.
• Second, how do we confirm when the customer has found all the bugs. This is normally achieved by looking at the history of the customer.

Testing Interview Questions

1. What is functional system testing ?

Testing the end to end functionality of the system as a whole.

2. What is the benefits of Independent Testing

Independent testers see other and different defects and are unbiased.  

3. In a REACTIVE approach to testing when would you expect the bulk of the test design work to be begun?

After the software or system has been produced.

4. What are the different Methodologies in Agile Development Model?

There are currently seven different Agile methodologies that I am aware of:

1.  Extreme Programming (XP)
2.  Scrum
3.  Lean Software Development
4.  Feature-Driven Development
5.  Agile Unified Process
6.  Crystal
7.  Dynamic Systems Development Model (DSDM) 

5. Which activity in the fundamental test process includes evaluation of the testability of the requirements and system?

A Test analysis and design.

6. What is typically the MOST important reason to use risk to drive testing efforts?

  Because testing everything is not feasible.  

7. Which is the MOST important advantage of independence in testing?

An independent tester may be more effective at finding defects missed by the person who wrote the software.  

8. Which of the following are valid objectives for incident reports?

i. Provide developers and other parties with feedback about the problem to enable identification, isolation and correction as necessary.

ii. Provide ideas for test process improvement.

iii. Provide a vehicle for assessing tester competence.

iv. Provide testers with a means of tracking the quality of the system under test.

i. Provide developers and other parties with feedback about the problem to enable identification, isolation and correction as necessary,

ii.Provide ideas for test process improvement,

iv.Provide testers with a means of tracking the quality of the system under test

9. Consider the following techniques. Which are static and which are dynamic techniques?

i. Equivalence Partitioning.

ii. Use Case Testing.

iii.Data Flow Analysis.

iv.Exploratory Testing.

v. Decision Testing.

vi. Inspections.

Data Flow Analysis and Inspections are static, Equivalence Partitioning, Use Case Testing, Exploratory Testing and Decision Testing are dynamic.

10. Why are static testing and dynamic testing described as complementary?

Because they share the aim of identifying defects but differ in the types of defect they find.  

11. What are the phases of a formal review ?

In contrast to informal reviews, formal reviews follow a formal process. A typical formal review process consists of six main steps:

1.  Planning
2.  Kick-off
3.  Preparation
4.  Review meeting
5.  Rework
6.  Follow-up.  

12. What is the role of moderator in review process?

The moderator (or review leader) leads the review process. He or she deter-mines, in co-operation with the author, the type of review, approach and the composition of the review team. The moderator performs the entry check and the follow-up on the rework, in order to control the quality of the input and output of the review process. The moderator also schedules the meeting, disseminates documents before the meeting, coaches other team members, paces the meeting, leads possible discussions and stores the data that is collected.

13. What is an equivalence partition (also known as an equivalence class)?

An input or output range of values such that only one value in the range becomes a test case.  

14. When should configuration management procedures be implemented?

During test planning.

15. A Type of functional Testing, which investigates the functions relating to detection of threats, such as virus from malicious outsiders.

Security Testing  

16. Testing where in we subject the target of the test , to varying workloads to measure and evaluate the performance behaviors and ability of the target and of the test to continue to function properly under these different workloads. Load Testing

17. Testing activity which is performed to expose defects in the interfaces and in the interaction between integrated components is:

Integration Level Testing  

18. What are the Structure-based (white-box) testing techniques ?

Structure-based testing techniques (which are also dynamic rather than static) use the internal structure of the software to derive test cases. They are com-monly called 'white-box' or 'glass-box' techniques (implying you can see into the system) since they require knowledge of how the software is implemented, that is, how it works. For example, a structural technique may be concerned with exercising loops in the software. Different test cases may

19. What is the KEY difference between preventative and reactive approaches to testing? 

Preventative tests are designed early; reactive tests are designed after the software has been produced.

20. What is the purpose of exit criteria? 

To define when a test level is complete.

21. What determines the level of risk? 

  The likelihood of an adverse event and the impact of the event

22. What is the MAIN objective when reviewing a software deliverable?

To identify defects in any software work product.

23. Which of the following defines the expected results of a test? Test case specification or test design specification.

Test case specification.

24. Which is a benefit of test independence?

It avoids author bias in defining effective tests.  

25. As part of which test process do you determine the exit criteria?

Test planning.  

26. Rapid Application Development ?

Rapid Application Development (RAD) is formally a parallel development of functions and subsequent integration. Components/functions are developed in parallel as if they were mini projects, the developments are time-boxed, delivered, and then assembled into a working prototype. This can very quickly give the customer something to see and use and to provide feedback regarding the delivery and their requirements. Rapid change and development of the product is possible using this methodology. However the product specification will need to be developed for the product at some point, and the project will need to be placed under more formal controls prior to going into production.

27. What is the difference between Testing Techniques and Testing Tools?

Testing technique: - Is a process for ensuring that some aspects of the application system or unit functions properly there may be few techniques but many tools.

Testing Tools: - Is a vehicle for performing a test process. The tool is a resource to the tester, but itself is insufficient to conduct testing . 

28. We use the output of the requirement analysis, the requirement specification as the input for writing ...

User Acceptance Test Cases  

29. Repeated Testing of an already tested program, after modification, to discover any defects introduced or uncovered as a result of the changes in the software being tested or in another related or unrelated software component:

Regression Testing

30. What is component testing ?

Component testing, also known as unit, module and program testing, searches for defects in, and verifies the functioning of software (e.g. modules, programs, objects, classes, etc.) that are separately testable. Component testing may be done in isolation from the rest of the system depend-ing on the context of the development life cycle and the system. Most often stubs and drivers are used to replace the missing software and simulate the interface between the software components in a simple manner. A stub is called from the software component to be tested; a driver calls a component to be tested.

31. When should be performed Regression testing ?

After the software has changed or when the environment has changed

32. When should testing be stopped?

It depends on the risks for the system being tested

33. What is the purpose of a test completion criterion?

To determine when to stop testing  

34. What can static analysis NOT find?

For example memory leaks  

35. What is the difference between re-testing and regression testing?

Re-testing ensures the original fault has been removed; regression testing looks for unexpected sideeffects  

36. What are the Experience-based testing techniques ?

In experience-based techniques, people's knowledge, skills and background are a prime contributor to the test conditions and test cases. The experience of both technical and business people is important, as they bring different perspectives to the test analysis and design process. Due to previous experience with similar systems, they may have insights into what could go wrong, which is very useful for testing.  

37."How much testing is enough?"

The answer depends on the risk for your industry, contract and special requirements. 51. When should testing be stopped? It depends on the risks for the system being tested.  

38. What is the difference between re-testing and regression testing?

  Re-testing ensures the original fault has been removed; regression testing looks for unexpected side-effects.  

39. Why we use decision tables?.

The techniques of equivalence partitioning and boundary value analysis are often applied to specific situations or inputs. However, if different combinations of inputs result in different actions being taken, this can be more difficult to show using equivalence partitioning and boundary value analysis, which tend to be more focused on the user interface. The other two specification-based tech-niques, decision tables and state transition testing are more focused on business logic or business rules. A decision table is a good way to deal with combinations of things (e.g. inputs). This technique is sometimes also referred to as a 'cause-effect' table. The reason for this is that there is an associated logic diagramming technique called 'cause-effect graphing' which was sometimes used to help derive the decision table

40. Faults found should be originally documented by who?

By testers.  

41. Why does the boundary value analysis provide good test cases?

Because errors are frequently made during programming of the different cases near the 'edges' of the range of values.  

42. What makes an inspection different from other review types?

It is led by a trained leader, uses formal entry and exit criteria and checklists.

43. Why can be tester dependent on configuration management?

Because configuration management assures that we know the exact version of the testware and the test object.

44. What is a V-Model ?

A software development model that illustrates how testing activities integrate with software development phases

45. What is maintenance testing?

Triggered by modifications, migration or retirement of existing software  

46. What is test coverage?

Test coverage measures in some specific way the amount of testing performed by a set of tests (derived in some other way, e.g. using specification-based techniques). Wherever we can count things and can tell whether or not each of those things has been tested by some test, then we can measure coverage.  

47. What is Alpha testing?

Pre-release testing by end user representatives at the developer's site.

48. What is a failure?

Failure is a departure from specified behaviour.  

Regression Testing: Manual or Automated?

The inquiry emerging at each one phase of advancement is that relapse after every emphasis takes excessively long, and the practicality being checked frequently had no progressions. Therefore, the likelihood of deformities is low. As a common consequence, we touch base at a thought to robotize all relapse situations and reject manual regression testing. The preferences here are self-evident: 

• mechanized tests could be performed at whatever time
• mechanized tests are extremely exact
• mechanization could be utilized as a part of very nearly all testing methods 
• programmed making of reports.

At the same time tragically, relapse tests robotization has numerous pitfalls that are seldom talked about. 

When you begin to mechanize relapse testing is important to understand a couple of inquiries: 

• What practicality is to be secured by the tests
• Auto tests architecture. 
• Decision of an apparatus for regression test automation.

At the phase of changing from manual testing to automation tests, I got a task where I needed to test the enrollment of two sorts of records for the site on 43 spaces relying upon the nation. It was as hell-fire. The customer couldn't have cared less about the nature of the data showed. The necessities were as takes after: 

• accounts are made without any lethal blunders; 
• information data corresponds with the qualities ​​that are shown in the settings after creation.

After a few runs I understood that I've had enough. At that minute I could just see that the amount of enlistment fields is diverse for a few nations, and I likewise had some coding background in C#. An alternate relapse was close nearby and I couldn't waver. I asked my companion acquainted with mechanization to advise and demonstrate to compose tests. After numerous inquiries, tries and lapses a straightforward route test was conceived. I uncovered locators and Selenium web drivers – and lo and view, all the areas utilized the same locators. I had somewhat left to do – to run the last manual relapse in my life on all areas and fill the table with the fields and relating spaces. An alternate round of manual relapse – a long process with finishing the table – and appears as though is everywhere. 

This proceeded for a few discharges until the organization chose to robotize the majority of the usefulness formally. Since the customer was not knowledgeable in mechanization tests we chose to robotize any that is inside my learning on test computerization. 

Subsequently, we have secured very nearly the whole framework with autotests. All might be fine, however after any fixes a few tests began to fall flat. For the most part, it happened due to long scripts that hold a great deal of steps: 

Long situations hold much code and activities like that; subsequently, rehashing the first step may prompt disappointment of numerous tests. 

Due to the code redundancy, auto tests check the same point for ordinarily; this effects in unnecessary expanding of the test span. 

Give us a chance to think about an alternate extremely fascinating circumstance. The customer requested autotests not surprisingly and required to compose a couple from cases. He affirmed the thought, and in a few days we added test robotization to the arrangement. Anyhow our programmers finished not meet the due date, in the long run we needed to compose autotests dependent upon the current stage. With a deferral of a few days programmers had a discharge, yet more than a large portion of autotests fizzled. 

Just a brief time prior we had one more entertaining circumstance. We had gained a request for site mechanizing and have completed everything rapidly. A couple of weeks after the fact the client sent a letter grumbling that tests completed not work. As it turned out, he began a site upgrade and all the tests had fizzled. 

Accordingly, the preferences of manual testing are seen obviously – it doesn't rely on upon anything and might be carried out constantly. Surrendering manual testing will bring no good thing. Robotized and manual testing are interrelated and integral testing systems and every has stars and cos. When considering relapse situations robotization think about time consumptions for both composing tests and their backing. Additionally, give careful consideration that manual masters are normally paid less than the individuals who have abilities on test mechanization. 

What is TestNG?

So far we had been doing Selenium tests without creating a legitimate configuration for the test outcomes. Starting here on, we might handle how to make these reports utilizing a test schema called Testing.

Testing is a trying skeleton that conquers the restrictions of an alternate mainstream testing system called Junit. The "NG" signifies "Cutting edge". Most Selenium clients utilize this more than Junit in view of its favorable circumstances. There are such a variety of characteristics of Testing, yet we will just concentrate on the most paramount ones that we can use in Selenium.

Advantages of TestNG over JUnit

Preferences of Testing over Junit

There are three significant preferences of Testing over Junit:

Annotations are simpler to get it

Test cases might be gathered all the more effortlessly

Parallel testing is conceivable

Why do we require Testing in Selenium?

Testing can create reports dependent upon our Selenium test outcomes.

Webdriver has no local instrument for producing reports.

Testing can produce the report in an intelligible organization.

Testing streamlines the way the tests are coded

The arrangement of activities is directed by straightforward annotations that don't oblige techniques to be static.

Web driver importent questions

 1.  What is webdriver?

 WebDriver is a simpler, more concise programming interface in addition to addressing some limitations in  the Selenium-RC API. Selenium-WebDriver was developed to better support dynamic webpages where elements of a page may change without the page itself being reloaded. WebDriver’s goal is to supply a well-designed object-oriented API that provides improved support for modern advanced web-app testing problems.

2.      What are the advantages of selenium2.0/webdriver?

•         Need no server to start
•     Easy to code
•         Has sophisticated API to support wide verity of browsers.
•     Supports to test dynamic UI web apps.

3.      Difference between the selenium1.0 and selenium 2.0?

Selenium 1.0	Selenium 2.0/Webdriver
1.      It ‘injected’ javascript functions into the browser when the browser was loaded and then used its javascript to drive the AUT within the browser. 2.      Selenium server need to start to run tests 3.      Has some loop-holes in supporting complex UI apps,Javascript security 4.      No support for headless broswers	1.      WebDriver makes directcalls to the browser using each browser’s native support for automation       2.      Not needed unless tests are run on local machine. 3.      Supports even drag and drop features and no security loop-holes 4.      Supports htmlunit driver –headless browser runs fast

4.      What are the Locators are there in selenium 2.0?

It supports locators based on Id,name,xpath,dom,css,class,tagname

5.      How to handle the Ajax Applications in Web driver?

There are 2 types of waits webdriver supports to handle ajax applications to make webdrive sync to execution:

Implicit wait :

driver.manage().timeouts().implicitlyWait(20,TimeUnit.SECONDS);

Explicit wait:   WebDriverWait, FluentWait

WebElement strr = (new WebDriverWait(driver,30)).until(ExpectedConditions.presenceOfElementLocated(By.xpath("//*[starts-with(@id,'yui_3_4_0_1_137509')]/ul/li[2]/a")));

 6.      Difference between findelement() and findelements()?

     findELement will find the first matching element.

     findELements will all the matching elements. You'll probably need to loop through all the elements  returned.

7.      How to take the screen shots in seelnium2.0?

            File src2 = ((TakesScreenshot)driver).getScreenshotAs(OutputType.FILE);

           

8.  What is the limitations of web driver?

• Can not automate desktop applications, supports only web applications
•  No inbuilt commands to generate good reports
• Cannot support readily for new browsers

Selenium IDE..

1)  What is Selenium IDE ?

The Selenium IDE is basically something having record & playback options & also has very good user interface. The core part of Selenium IDE is based on JavaScript & also supports different extension in it. Along with record & playback, you can use Selenium IDE for multiple dynamic stuffs. The main limitation of Selenium IDE is that, it supported in only Firefox browser. If you want to execute your scripts on different browsers, then you can use Selenium RC (Selenium Remote Control). The Selenium RC supports multiple browsers like IE, Firefox, Chrome, Safari, Opera etc. 

2)  How to install Selenium IDE ?

A)  click here for detailed steps  

      I use seleniumhq.org site to download any software regarding selenium.. Here, if we click on the version number of selenium ide it starts downloading the add-ons, just we have to click on 'install now' button and restart the firefox browser.. With-in 5 minutes we can install selenium ide...  

3)  Features of selenium IDE..

• Its main feature is record and playback..
• Debugging features by setting breakpoints, startpoints, pause..
• Identifies element using id, name, xpath etc..
• Auto complete for all common selenium commands..
• It has an option of asserting title of every page automatically..
• Support for selenium user-extensions.js file..
• Option to run single test or multiple tests(suite).
• It has a feature of exporting testcase/suite into different formats like C#, Java, Ruby, Python..

4)  Advantages and disadvantages of selenium IDE..

A)  Advantages : 

• Freeware..
• Easy to install..
• It is the only flavor of selenium that allows us to record user actions on browser window.. 
•  Scripts recorded in IDE can be coverted into other languages like Java, C#, Python and Ruby..
• It is not only a time saver but also an excellent way of learning scripts syntax..
• We can insert comments in the middle of the script for better understanding and debugging..
• Context menu, which allows us to pick from a list of assertions and verifications for the selected location..

Disadvantages:

• Main disadvantage of IDE is that it runs only in firefox browser..
• Selenium IDE can execute scripts created in selenese only.
• Cannot upload files..
• It does not directly support loops and conditions..
• Reading from external files like .txt, .xls is not possible..

5)  How do you locate elements in IDE ?

A)  I will focus on the unique attribute values like id, name or other structural information that is stable enough to withstand frequent changes to the web application.. I strongly recommend CSS selectors as locating strategy.. They are considerably faster than xpath and can find the most complicated objects in any HTML document..

6)  What is selenese ?
There are three types of selenese..

1. Actions : They perform some operations like clicking a link or typing text in text box or selecting an option from drop-down box etc..
2. Assertions : They verify that the state of application conforms to what is expected.. Ex: 'verify that this checkbox is checked', 'make sure that the page title is X'..
3. Accessors : Checks the state of application and store the results in a variable.. Ex: storeText, storeTitle, etc..

 How do you add check points or verification points ?
A)  They are called as Assertions in selenium.. 'assert', 'verify' and 'waitFor' are the commands used to add check points..
Ex: assertText, verifyElementPresent, waitForTextPresent, etc..

10)  Name some commands that you use frequently in IDE ?
A)  Open, click, type, select, assertText, assertTitle, assertTextPresent, verifyText, verifyTextPresent, veriftTitle, waitForText, waitForTextPresent, waitForTitle, store, storeText, storeTitle, check, uncheck, pause, mouseover, etc..

11)  What is the difference between assert and verify ?
A)   When an 'assert' fails, the test is aborted where as when 'verify' fails, the test will continue execution logging the failure..
'assert' is used when the expected value is mandatory to continue with next set of steps.. However 'verify' is used when the expected value is optional to continue with the next set of steps..

12)  Difference between waitFor and pause commands ?
A)  'waitFor' command waits for some condition to become true..
For example, 'waitForPageToLoad(20000)'-- it will wait upto 20 thousand milliseconds to load required page.. If the page is loaded before 20,000ms then it jumps to next step to execute.. If the page is not loaded before 20,000ms then it stops the execution due to time-out error..

 Pause command stops the execution of the test until the specified time..
Ex:  pause(10000)-- It stops the execution of test for 1o thousand milliseconds.. After completing 10,000ms it jumps to next command to execute.. I prefer 'waitFor' command than 'pause'..