Sunday, 17 June 2018

Software Testing Interview questions asked in ClearTrip



1.       What is the difference between http and https? Give some examples.
2.       What do you understand by Web Services?
3.       What is REST API?
4.       What are the http errors which we get while testing an API? Name few.
5.       What is the difference between cache and cookies? Explain giving a real world example.
6.       What are different types of cookies?
7.       Given a Scenario: - On opening a webpage if no content is displayed (blank page is displayed) then how will you debug it?
8.       Given a Scenario: - There is a movie review portal webpage. Viewers can view the reviews of a movie, like it and can add his/her comments.
Every comment is not directly posted on the webpage. The comment first goes to the page Admin, he has to review the comment and then either Accept/Reject. Only accepted comments get posted on the webpage.
Tell the test scenarios which you will write to test this webpage.
9.       Write an SQL query to find out employee name having maximum salary from table emp_details (having  emp_name, emp_id & dept) and emp_salary (having emp_id and emp_sal).
10.   How do you deploy builds in your current organization?
11.   What could be the root cause when customers are not receiving OTP or if they are receiving OTP’s they are delayed?
12.   How will you simulate customer’s environment in your test environment if you want to replicate a bug (which is not replicable in test servers)?
13.   Given a Scenario :- Product manager of BookMyShow App comes up with a new requirement of adding a new feature of sending details of booked movie tickets over customers e-mail (along with text messages).

Is the above mentioned requirement complete? If No, what are the missing details you would want as a QA?
14.   How will you test a network issue caused in your test environment?
15.   What do you understand by regression testing, sanity testing and retesting? Explain with help of examples.
16.   How will you do performance testing using JMeter?
17.   What problems could be faced during performance testing for 100 users via JMeter?
18.   What is the difference between PUT and POST?
19.   Write a java program accepting following input and giving following outputs :-
Input: - My name is Alexander
Output 1: - rednaxelA si eman ym
Output 2: - Alexander is My name
20.   Write a java program to check if all the open braces are closed in a given line of code (in java).
21.   What is the command to find the free memory space in Selenium?
22.   What is the Linux command to work on the same window where a particular script is being executed?
23.   What could be the logic behind Amazon showing different sections saying :-
1.       “People who bought this product also bought the following :-“

2.       “People who viewed this product bought the following :-“


All The Best.


Saturday, 16 June 2018

What is Marker interface?



The marker interface is a design pattern, used with languages that provide run-time type information about objects. It provides a way to associate metadata with a class where the language does not have explicit support for such metadata. To use this pattern, a class implements a marker interface, and code that interact with instances of that class test for the existence of the interface. Whereas a typical interface specifies methods that an implementing class must support, a marker interface does not do so.

Marker interface in java is an interface which does not have any method. Marker interface is used to inform the JVM that the classes implementing them will have some special behavior.

Example of Marker interfaces are:-


  • java.io.Serializable - Serializability of a class is enabled by the class implementing the java.io.Serializable interface. The Java Classes that do not implement Serializable interface will not be able to serialize or deserializ their state. All subtypes of a serializable class are themselves serializable. The serialization interface has no methods or fields and serves only to identify the semantics of being serializable.
  • java.rmi.Remote - The Remote interface serves to identify interfaces whose methods may be invoked from a non-local virtual machine. Any object that is a remote object must directly or indirectly implement this interface. Only those methods specified in a "remote interface", an interface that extends java.rmi.Remote are available remotely.
  • java.lang.Cloneable - A class implements the Cloneable interface to indicate to the Object.clone() method that it is legal for that method to make a field-for-field copy of instances of that class. Invoking Object's clone method on an instance that does not implement the Cloneable interface results in the exception CloneNotSupportedException being thrown.


The "instanceof" keyword in java can be used to test if an object is of a specified type. So this keyword in combination with Marker interface can be used to take different actions based on type of interface an object implements.

Enjoy Reading.

Static variables in Java



A static variable is associated with the class as a whole rather than with specific instances of a
class. Each object will share a common copy of the static variables i.e. there is only one copy per
class, no matter how many objects are created from it. Class variables or static variables are
declared with the static keyword in a class. These are declared outside a class and stored in
static memory. Class variables are mostly used for constants.

Static variables are always called by the class name. This variable is created when the program starts and gets destroyed when the programs stops. The scope of the class variable is same an instance variable.
Its initial value is same as instance variable and gets a default value when its not initialized corresponding to the data type. Similarly, a static method is a method that belongs to the class rather than any object of the class and doesn’t apply to an object or even require that any objects of the class have been instantiated.

Example:-
public class SampleProgram {  
      static int i = 1;  
      public static void main(String[] args) {  
           System.out.println("Initial Value:" + i);  
           incrementAndDisplay();  
      }  
      private static void incrementAndDisplay() {  
           i = i + 2;  
           System.out.println("After increment:" + i);  
      }  
 }  

Output:-

Initial Value:1
After increment:3

Static methods are implicitly final, because overriding is done based on the type of the object, and
static methods are attached to a class, not an object. A static method in a superclass can be
shadowed by another static method in a subclass, as long as the original method was not
declared final. However, you can’t override a static method with a non-static method. In other
words, you can’t change a static method into an instance method in a subclass.

Non-static variables take on unique values with each object instance.


Enjot Reading.

Why String class is immutable?



Strings implemented as final or immutable objects.It provides lot of advantages in its usage. Below are some advantages of String Immutability in Java


  • Immutable objects are thread-safe. Two threads can both work on an immutable object at the same time without any possibility of conflict.
  • Security: the system can pass on sensitive bits of read-only information without worrying that it will be altered
  • You can share duplicates by pointing them to a single instance.
  • You can create substrings without copying. You just create a pointer into an existing base String guaranteed never to change. Immutability is the secret that makes Java substring implementation very fast.
  • Immutable objects are good fit for becoming Hashtable keys. If you change the value of any object that is used as a hash table key without removing it and re-adding it you will lose the object mapping.
  • Since String is immutable, inside each String is a char[] exactly the correct length. Unlike a StringBuilder there is no need for padding to allow for growth.
  • If String were not final, you could create a subclass and have two strings that look alike when "seen as Strings", but that are actually different.

Enjoy Reading.

What is immutable object in Java?



A Java object is considered immutable when its state cannot change after it is created. Use of immutable objects is widely accepted as a sound strategy for creating simple, reliable code.

Immutable objects are particularly useful in concurrent applications. Since they cannot change state, they cannot be corrupted by thread interference or observed in an inconsistent state. java.lang.String and java.lang.Integer classes(All Wrapper Classes) are the Examples of immutable objects from the JDK.

Advantage/benefits of Immutable Objects:-


  • Immutable objects are simple to use test and construct.
  • Immutable objects are automatically thread-safe.
  • Immutable objects do not require a copy constructor.
  • Immutable objects do not require an implementation of clone.
  • Immutable objects allow hashCode to use lazy initialization, and to cache its return value.
  • Immutable objects do not need to be copied defensively when used as a field.
  • Immutable objects are good Map keys and Set elements (Since state of these objects must not change while stored in a collection).
  • Immutable objects have their class invariant established once upon construction, and it never needs to be checked again.
  • Immutable objects always have "failure atomicity" (a term used by Joshua Bloch) : if an immutable object throws an exception, it's never left in an undesirable or indeterminate state.

Enjoy Reading.

Java program execution inside JVM



When JVM executes a Java application, a runtime instance of JVM is born.This runtime instance invoke main() method of Java application.The main() method of an application serves as the starting point for that application's initial thread. The initial thread can in turn fire off other threads.

This thread has a program counter(PC) and Java stack.Whenever main() method is invoked, a stack frame is pushed onto the stack,this then becomes the active tack frame.The program counter in the new Java stack frame will point to the beginning of the method.

If there are more method invocations within main() method then this process of pushing new stack frame onto the stack for each method call is repeated as and when they are invoked.When a method returns, the active frame is popped from the stack and the one below becomes the active stack frame.The PC is set to the instruction after the method call and the method continues.

There is only one heap corresponding to an instance of JVM and all objects created are stored here.This heap is shared by all threads created in an application.

Inside the Java virtual machine, threads come in two flavors: daemon and non- daemon. A daemon thread is ordinarily a thread used by the virtual machine itself, such as a thread that performs garbage collection. The application, however, can mark any threads it creates as daemon threads. The initial thread of an application--the one that begins at main()--is a non- daemon thread.

A Java application continues to execute (the virtual machine instance continues to live) as long as any non-daemon threads are still running. When all non-daemon threads of a Java application terminate, the virtual machine instance will exit. If permitted by the security manager, the application can also cause its own demise by invoking the exit() method of class Runtime or System.

When main() returns,it terminates the application's only non-daemon thread, which causes the virtual machine instance to exit.

Enjoy Reading

Hibernate Interview Questions and Answers



1. What is Hibernate?
Hibernate is a powerful, high performance object/relational persistence and query service.
This lets the users to develop persistent classes following object-oriented principles such
as association, inheritance, polymorphism, composition, and collections.

2. What is ORM?
ORM stands for Object/Relational mapping. It is the programmed and translucent
perseverance of objects in a Java application in to the tables of a relational database using
the metadata that describes the mapping between the objects and the database. It works
by transforming the data from one representation to another.

3. What does an ORM solution comprises of?
• It should have an API for performing basic CRUD (Create, Read, Update, Delete)
operations on objects of persistent classes
• Should have a language or an API for specifying queries that refer to the classes
and the properties of classes
• An ability for specifying mapping metadata
• It should have a technique for ORM implementation to interact with transactional
objects to perform dirty checking, lazy association fetching, and other optimization
functions

4. What are the different levels of ORM quality?
There are four levels defined for ORM quality.
i. Pure relational
ii. Light object mapping
iii. Medium object mapping
iv. Full object mapping

5. What is a pure relational ORM?
The entire application, including the user interface, is designed around the relational
model and SQL-based relational operations.

6. What is a meant by light object mapping?
The entities are represented as classes that are mapped manually to the relational tables.
The code is hidden from the business logic using specific design patterns. This approach
is successful for applications with a less number of entities, or applications with common,
metadata-driven data models. This approach is most known to all.

7. What is a meant by medium object mapping?
The application is designed around an object model. The SQL code is generated at build
time. And the associations between objects are supported by the persistence mechanism,
and queries are specified using an object-oriented expression language. This is best suited
for medium-sized applications with some complex transactions. Used when the mapping
exceeds 25 different database products at a time.

8. What is meant by full object mapping?
Full object mapping supports sophisticated object modeling: composition, inheritance,
polymorphism and persistence. The persistence layer implements transparent persistence;
persistent classes do not inherit any special base class or have to implement a special
interface. Efficient fetching strategies and caching strategies are implemented
transparently to the application.

9. What are the benefits of ORM and Hibernate?
There are many benefits from these. Out of which the following are the most important
one.
i. Productivity – Hibernate reduces the burden of developer by providing much of
the functionality and let the developer to concentrate on business logic.
ii. Maintainability – As hibernate provides most of the functionality, the LOC for the
application will be reduced and it is easy to maintain. By automated object/relational
persistence it even reduces the LOC.
iii. Performance – Hand-coded persistence provided greater performance than
automated one. But this is not true all the times. But in hibernate, it provides more
optimization that works all the time there by increasing the performance. If it is
automated persistence then it still increases the performance.
iv. Vendor independence – Irrespective of the different types of databases that are
there, hibernate provides a much easier way to develop a cross platform application.

10. How does hibernate code looks like?
Session session = getSessionFactory().openSession();
Transaction tx = session.beginTransaction();
MyPersistanceClass mpc = new MyPersistanceClass ("Sample App");
session.save(mpc);
tx.commit();
session.close();
The Session and Transaction are the interfaces provided by hibernate. There are many
other interfaces besides this.

11. What is a hibernate xml mapping document and how does it look like?
In order to make most of the things work in hibernate, usually the information is provided
in an xml document. This document is called as xml mapping document. The document
defines, among other things, how properties of the user defined persistence classes’ map
to the columns of the relative tables in database.
<?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC
"http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">
<hibernate-mapping>
<class name="sample.MyPersistanceClass" table="MyPersitaceTable">
<id name="id" column="MyPerId">
<generator class="increment"/>
</id>
<property name="text" column="Persistance_message"/>
<many-to-one name="nxtPer" cascade="all" column="NxtPerId"/>
</class>
</hibernate-mapping>
Everything should be included under <hibernate-mapping> tag. This is the main tag for
an xml mapping document.
`
12. What the Core interfaces are of hibernate framework?
There are many benefits from these. Out of which the following are the most important
one.
i. Session Interface – This is the primary interface used by hibernate applications.
The instances of this interface are lightweight and are inexpensive to create and destroy.
Hibernate sessions are not thread safe.
ii. SessionFactory Interface – This is a factory that delivers the session objects to
hibernate application. Generally there will be a single SessionFactory for the whole
application and it will be shared among all the application threads.
iii. Configuration Interface – This interface is used to configure and bootstrap
hibernate. The instance of this interface is used by the application in order to specify the
location of hibernate specific mapping documents.
iv. Transaction Interface – This is an optional interface but the above three interfaces
are mandatory in each and every application. This interface abstracts the code from any
kind of transaction implementations such as JDBC transaction, JTA transaction.
v. Query and Criteria Interface – This interface allows the user to perform queries
and also control the flow of the query execution.

13. What are Callback interfaces?
These interfaces are used in the application to receive a notification when some object
events occur. Like when an object is loaded, saved or deleted. There is no need to
implement callbacks in hibernate applications, but they’re useful for implementing
certain kinds of generic functionality.

14. What is the file extension you use for hibernate mapping file?
The name of the file should be like this : filename.hbm.xml
The filename varies here. The extension of these files should be “.hbm.xml”.
This is just a convention and it’s not mandatory. But this is the best practice to follow this
extension.

15. What do you create a SessionFactory?
Configuration cfg = new Configuration();
cfg.addResource("myinstance/MyConfig.hbm.xml");
cfg.setProperties( System.getProperties() );
SessionFactory sessions = cfg.buildSessionFactory();
First, we need to create an instance of Configuration and use that instance to refer to the
location of the configuration file. After configuring this instance is used to create the
SessionFactory by calling the method buildSessionFactory().

16. What is meant by Method chaining?
Method chaining is a programming technique that is supported by many hibernate
interfaces. This is less readable when compared to actual java code. And it is not
mandatory to use this format. Look how a SessionFactory is created when we use method
chaining.
SessionFactory sessions = new Configuration()
.addResource("myinstance/MyConfig.hbm.xml")
.setProperties( System.getProperties() )
.buildSessionFactory();

17. What does hibernate.properties file consist of?
This is a property file that should be placed in application class path. So when the
Configuration object is created, hibernate is first initialized. At this moment the
application will automatically detect and read this hibernate.properties file.
hibernate.connection.datasource = java:/comp/env/jdbc/AuctionDB
hibernate.transaction.factory_class =
net.sf.hibernate.transaction.JTATransactionFactory
hibernate.transaction.manager_lookup_class =
net.sf.hibernate.transaction.JBossTransactionManagerLookup
hibernate.dialect = net.sf.hibernate.dialect.PostgreSQLDialect

18. What should SessionFactory be placed so that it can be easily accessed?
As far as it is compared to J2EE environment, if the SessionFactory is placed in JNDI
then it can be easily accessed and shared between different threads and various
components that are hibernate aware. You can set the SessionFactory to a JNDI by
configuring a property hibernate.session_factory_name in the hibernate.properties file.

19. What are POJOs?
POJO stands for plain old java objects. These are just basic JavaBeans that have defined
setter and getter methods for all the properties that are there in that bean. Besides they
can also have some business logic related to that property. Hibernate applications works
efficiently with POJOs rather then simple java classes.

20. What is object/relational mapping metadata?
ORM tools require a metadata format for the application to specify the mapping between
classes and tables, properties and columns, associations and foreign keys, Java types and
SQL types. This information is called the object/relational mapping metadata. It defines
the transformation between the different data type systems and relationship
representations.

21. What is HQL?
HQL stands for Hibernate Query Language. Hibernate allows the user to express queries
in its own portable SQL extension and this is called as HQL. It also allows the user to
express in native SQL.

22. What are the different types of property and class mappings?
• Typical and most common property mapping
<property name="description" column="DESCRIPTION" type="string"/>
Or
<property name="description" type="string">
<column name="DESCRIPTION"/>
</property>
• Derived properties
<property name="averageBidAmount" formula="( select AVG(b.AMOUNT) from BID b
where b.ITEM_ID = ITEM_ID )" type="big_decimal"/>
• Typical and most common property mapping
<property name="description" column="DESCRIPTION" type="string"/>
• Controlling inserts and updates
<property name="name" column="NAME" type="string"
insert="false" update="false"/>


23. What are the different approaches to represent an inheritance hierarchy?
i. Table per concrete class.
ii. Table per class hierarchy.
iii. Table per subclass.

Enjoy Reading.