The Thread Group tells JMet%r the number of usars you want to simulate, how ofteî the users should send requests, and the how many requests they should send.

Select the Thread Group element in the tree, if you have not already selected it. You should now see the Thread Group Control Panel in the right section of the JMeter window (see Figure 9.2 below)

Figure 9.2. Thread Group with Default Values

Start by providing a more descriptive name for our Thread Group. In the name field, enter JMeter Users.

Next, increase the number of users (called threads) to 10.

In the next field, the Ramp-Up Period, leave the default value of 0 seconds. This property tells JMeter how long to delay between starting each user. For example, if you enter a Ramp-Up Period of 5 seconds, JMeter will finish starting all of your users by the end of the 5 seconds. So, if we have 5 users and a 5 second Ramp-Up Period, then the delay between starting users would be 1 second (5 users / 5 seconds = 1 user per second). If you set the value to 0, then JMeter will immediately start all of your users.

Finally, clear the checkbox labeled "Forever", and enter a value of 2 in the Loop Count field. This property tells JMeter how many times to repeat your test. If you enter a loop count value of 0, then JMeter will run your test only once. To have JMeter repeatedly run your Test Plan, select the Forever checkbox.

See Figure 9.2 for the completed JMeter Users Thread Group.

Figure 9.3. JMeter Users Thread Group

The final element you need to add to your Test Plan is a Listener. This element is responsible for storing all of the results of your HTTP requests in a file and presenting a visual model of the data.

Select the JMeter Users element and add a Aggregate Graph listener ( Add → Listener → Aggregate Graph ). Next, you need to specify a directory and filename of the output file. You can either type it into the filename field, or select the Browse button and browse to a directory and then enter a filename.

Figure 9.4. Graph Results Listener

Testing a REST Webservice is very similar as you only need to modify in HTTP Request

• Method: to select the one you want to test
• Body Data: which can be JSON, XML or any custom text

You may also need to modify "HTTP Header Manager" to select the correct "Content-Type"