Parameterizing and Correlating Test Data In JMeter | Learn JMeter

 Parameterizing and correlating test data are important aspects of creating realistic and effective performance tests in JMeter. 

Let's explain each concept in detail:

Parameterizing Test Data:

Parameterizing test data is the process of replacing hard-coded test data in a test script with dynamic test data. 

This is useful when testing scenarios that involve a large number of users or when testing with different data sets. 

Parameterization allows the same script to be used with different data sets and creates a more realistic load on the application under test.

In JMeter, parameterizing test data can be achieved through the use of variables. Variables can be defined in the test plan and can be used to replace hard-coded test data in the test script. For example, a variable can be created to represent a user's login credentials. The variable can then be used in the test script to replace the hard-coded values for the login credentials.

JMeter provides several ways to parameterize test data, such as:

CSV Data Set Config: This allows you to read test data from a CSV file and use it in your test script. You can specify the file location and the column names that contain the test data.

User Defined Variables: This allows you to define variables in the test plan and use them in your test script. You can specify the variable name and the value that it should be set to.

Random Variable: This allows you to generate random values for test data. You can specify the range of values that the variable should take and the type of data it should be (e.g., integer, string).

Correlating Test Data:

Correlating test data is the process of capturing dynamic values from the server's response and passing them to subsequent requests. 

This is necessary when testing scenarios that involve multiple requests and responses, such as user authentication, session management, and shopping cart functionality.

In JMeter, correlating test data can be achieved through the use of regular expressions and extractors. Regular expressions are used to extract dynamic values from the server's response, and extractors are used to pass the extracted values to subsequent requests. For example, when testing an e-commerce website, a regular expression can be used to extract the session ID from the server's response, and an extractor can be used to pass the session ID to subsequent requests.

JMeter provides several ways to correlate test data, such as:

Regular Expression Extractor: This allows you to extract data from a server response using regular expressions. You can specify the regular expression and the name of the variable that the extracted data should be saved to.

JSON Extractor: This allows you to extract data from a JSON response. You can specify the JSON path and the name of the variable that the extracted data should be saved to.

XPath Extractor: This allows you to extract data from an XML response. You can specify the XPath expression and the name of the variable that the extracted data should be saved to.

Examples of parameterizing and correlating test data in JMeter:

Parameterizing Test Data Example:

Suppose you have a JMeter test plan for a login page that sends a username and password in the request body. Instead of using the same username and password for every iteration of the test, you can parameterize the test data using a CSV file.

Here are the steps to parameterize the test data:

• Add a CSV Data Set Config element to the test plan.

• Configure the CSV Data Set Config element with the path to the CSV file and the column names for the username and password.

• In the HTTP Request sampler, replace the hard-coded username and password values with variables.

• In the HTTP Request sampler, reference the variables in the Parameters section using the syntax ${variable_name}.

Here's an example of how the HTTP Request sampler might look after parameterizing the test data:

HTTP Request sampler
- Method: POST
- Path: /login
- Parameters:
  - username: ${username}
  - password: ${password}
 

Correlating Test Data Example:

Suppose you have a JMeter test plan for an e-commerce website that requires authentication. After the user logs in, the server sends back a session ID that is required for subsequent requests. You can use a regular expression extractor to extract the session ID and pass it to subsequent requests.

Here are the steps to correlate the test data:

• Add a Regular Expression Extractor element to the test plan.

• Configure the Regular Expression Extractor element with the regular expression to match the session ID and the name of the variable to save the value to.

• In the subsequent requests, reference the variable using the syntax ${variable_name}.

Here's an example of how the Regular Expression Extractor might be configured:

Regular Expression Extractor
- Apply to: Main sample and sub-samples
- Reference Name: sessionId
- Regular Expression: sessionId=(.+?); // assuming the session ID is returned in a cookie named sessionId
- Template: $1$
- Match No.: 1
 

Here's an example of how the subsequent requests might reference the variable:

HTTP Request sampler
- Method: GET
- Path: /cart
- Parameters:
  - sessionId: ${sessionId}