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What is difference between Performance Testing, Load Testing and Stress Testing?

Q. What is difference between Performance Testing, Load Testing and Stress Testing?

1) Performance Testing:

Performance testing is the testing, which is performed, to ascertain how the components of a system are performing, given a particular situation. Resource usage, scalability and reliability of the product are also validated under this testing. This testing is the subset of performance engineering, which is focused on addressing performance issues in the design and architecture of software product.

Performance Testing Goal:

The primary goal of performance testing includes establishing the benchmark behaviour of the system. There are a number of industry-defined benchmarks, which should be met during performance testing.

Performance testing does not aim to find defects in the application, it address a little more critical task of testing the benchmark and standard set for the application. Accuracy and close monitoring of the performance and results of the test is the primary characteristic of performance testing.


For instance, you can test the application network performance on Connection Speed vs. Latency chart. Latency is the time difference between the data to reach from source to destination. Thus, a 70kb page would take not more than 15 seconds to load for a worst connection of 28.8kbps modem (latency=1000 milliseconds), while the page of same size would appear within 5 seconds, for the average connection of 256kbps DSL (latency=100 milliseconds). 1.5mbps T1 connection (latency=50 milliseconds) would have the performance benchmark set within 1 second to achieve this target.

For example, the time difference between the generation of request and acknowledgement of response should be in the range of x ms (milliseconds) and y ms, where x and y are standard digits. A successful performance testing should project most of the performance issues, which could be related to database, network, software, hardware etc…

2) Load Testing:

Load testing is meant to test the system by constantly and steadily increasing the load on the system till the time it reaches the threshold limit. It is the simplest form of testing which employs the use of automation tools such as LoadRunner or any other good tools, which are available. Load testing is also famous by the names like volume testing and endurance testing.

The sole purpose of load testing is to assign the system the largest job it could possible handle to test the endurance and monitoring the results. An interesting fact is that sometimes the system is fed with empty task to determine the behaviour of system in zero-load situation.

Load Testing Goal:

The goals of load testing are to expose the defects in application related to buffer overflow, memory leaks and mismanagement of memory. Another target of load testing is to determine the upper limit of all the components of application like database, hardware and network etc… so that it could manage the anticipated load in future. The issues that would eventually come out as the result of load testing may include load balancing problems, bandwidth issues, capacity of the existing system etc…


For example, to check the email functionality of an application, it could be flooded with 1000 users at a time. Now, 1000 users can fire the email transactions (read, send, delete, forward, reply) in many different ways. If we take one transaction per user per hour, then it would be 1000 transactions per hour. By simulating 10 transactions/user, we could load test the email server by occupying it with 10000 transactions/hour.


3) Stress testing

Under stress testing, various activities to overload the existing resources with excess jobs are carried out in an attempt to break the system down. Negative testing, which includes removal of the components from the system is also done as a part of stress testing. Also known as fatigue testing, this testing should capture the stability of the application by testing it beyond its bandwidth capacity.

The purpose behind stress testing is to ascertain the failure of system and to monitor how the system recovers back gracefully. The challenge here is to set up a controlled environment before launching the test so that you could precisely capture the behaviour of system repeatedly, under the most unpredictable scenarios.

Stress Testing Goal:

The goal of the stress testing is to analyse post-crash reports to define the behaviour of application after failure. The biggest issue is to ensure that the system does not compromise with the security of sensitive data after the failure. In a successful stress testing, the system will come back to normality along with all its components, after even the most terrible break down.


As an example, a word processor like Writer1.1.0 by is utilized in development of letters, presentations, spread sheets etc… Purpose of our stress testing is to load it with the excess of characters.

To do this, we will repeatedly paste a line of data, till it reaches its threshold limit of handling large volume of text. As soon as the character size reaches 65,535 characters, it would simply refuse to accept more data. The result of stress testing on Writer 1.1.0 produces the result that, it does not crash under the stress and that it handle the situation gracefully, which make sure that application is working correctly even under rigorous stress conditions.

Database Testing – Practical Tips and Insight on How to Test Database

Database Testing – Practical Tips and Insight on How to Test Database

Database is one of the inevitable parts of a software application these days. It does not matter at all whether it is web or desktop, client server or peer to peer, enterprise or individual business, database is working at backend. Similarly, whether it is healthcare of finance, leasing or retail, mailing application or controlling spaceship, behind the scene a database is always in action.

Moreover, as the complexity of application increases the need of stronger and secure database emerges. In the same way, for the applications with high frequency of transactions (e.g. banking or finance application), necessity of fully featured DB Tool is coupled.

Currently, several database tools are available in the market e.g. MS-Access2010, MS SQL Server 2008 r2, Oracle 10g, Oracle Financial, MySQL, PostgreSQL, DB2 etc.  All of these vary in cost, robustness, features and security. Each of these DBs possesses its own benefits and drawbacks. One thing is certain; a business application must be built using one of these or other DB Tools.

Before I start digging into the topic, let me comprehend the foreword. When the application is under execution, the end user mainly utilizes the 'CRUD' operations facilitated by the DB Tool.

C: Create – When user 'Save' any new transaction, 'Create' operation is performed.
R: Retrieve – When user 'Search' or 'View' any saved transaction, 'Retrieve' operation is performed.
U: Update – when user 'Edit' or 'Modify' an existing record, the 'Update' operation of DB is performed.
D: Delete – when user 'Remove' any record from the system, 'Delete' operation of DB is performed.

It does not matter at all, which DB is used and how the operation is preformed. End user has no concern if any join or sub-query, trigger or stored-procedure, query or function was used to do what he wanted. But, the interesting thing is that all DB operations performed by user, from UI of any application, is one of the above four, acronym as CRUD.

Database Testing

As a database tester one should be focusing on following DB testing activities:

What to test in database testing:

1) Ensure data mapping:

Make sure that the mapping between different forms or screens of AUT and the Relations of its DB is not only accurate but is also according to design documents. For all CRUD operations, verify that respective tables and records are updated when user clicks 'Save', 'Update', 'Search' or 'Delete' from GUI of the application.

2) Ensure ACID Properties of Transactions:

ACID properties of DB Transactions refer to the 'Atomicity', 'Consistency', 'Isolation' and 'Durability'. Proper testing of these four properties must be done during the DB testing activity. This area demands more rigorous, thorough and keen testing when the database is distributed.

3) Ensure Data Integrity:

Consider that different modules (i.e. screens or forms) of application use the same data in different ways and perform all the CRUD operations on the data. In that case, make it sure that the latest state of data is reflected everywhere. System must show the updated and most recent values or the status of such shared data on all the forms and screens. This is called the Data Integrity.

4) Ensure Accuracy of implemented Business Rules:

Today, databases are not meant only to store the records. In fact, DBs have been evolved into extremely powerful tools that provide ample support to the developers in order to implement the business logic at DB level. Some simple examples of powerful features of DBs are 'Referential Integrity', relational constrains, triggers and stored procedures. So, using these and many other features offered by DBs, developers implement the business logic on DB level. Tester must ensure that the implemented business logic is correct and works accurately.

Above points describe the four most important 'What Tos' of database testing. Now, I will put some light on 'How Tos' of DB Testing. But, first of all I feel it better to explicitly mention an important point. DB Testing is a business critical task, and it should never be assigned to a fresh or inexperienced resource without proper training.

How To Test Database:

1. Create your own Queries

In order to test the DB properly and accurately, first of all a tester should have very good knowledge of SQL and specially DML (Data Manipulation Language) statements. Secondly, the tester should acquire good understanding of internal DB structure of AUT. If these two pre-requisites are fulfilled, then the tester is ready to test DB with complete confidence. (S)He will perform any CRUD operation from the UI of application, and will verify the result using SQL query.

This is the best and robust way of DB testing especially for applications with small to medium level of complexity. Yet, the two pre-requisites described are necessary. Otherwise, this way of DB testing cannot be adopted by the tester.

Moreover, if the application is very complex then it may be hard or impossible for the tester to write all of the needed SQL queries himself or herself. However, for some complex queries, tester may get help from the developer too. I always recommend this method for the testers because it does not only give them the confidence on the testing they have performed but, also enhance their SQL skill.

2. Observe data table by table

If the tester is not good in SQL, then he or she may verify the result of CRUD operation, performed using GUI of the application, by viewing the tables (relations) of DB. Yet, this way may be a bit tedious and cumbersome especially when the DB and tables have large amount of data.

Similarly, this way of DB testing may be extremely difficult for tester if the data to be verified belongs to multiple tables. This way of DB testing also requires at least good knowledge of Table structure of AUT.

3. Get query from developer

This is the simplest way for the tester to test the DB. Perform any CRUD operation from GUI and verify its impacts by executing the respective SQL query obtained from the developer. It requires neither good knowledge of SQL nor good knowledge of application's DB structure.

So, this method seems easy and good choice for testing DB. But, its drawback is havoc. What if the query given by the developer is semantically wrong or does not fulfill the user's requirement correctly? In this situation, the client will report the issue and will demand its fix as the best case. While, the worst case is that client may refuse to accept the application.



Database is the core and critical part of almost every software application. So DB testing of an application demands keen attention, good SQL skills, proper knowledge of DB structure of AUT and proper training.

In order to have the confident test report of this activity, this task should be assigned to a resource with all the four qualities stated above. Otherwise, shipment time surprises, bugs identification by the client, improper or unintended application's behavior or even wrong outputs of business critical tasks are more likely to be observed. Get this task done by most suitable resources and pay it the well-deserved attention.