LoadRunner Tutorial

5

Solving Common Playback Problems

After you create a script, you validate it by running it from VuGen.

Occasionally, a simple playback will fail, even though the recording of the

same actions succeeded.

Many applications use dynamic values that change each time you use the

application. For example, some servers assign a unique session ID for every

new session. When you try to replay a recorded session, the application

creates a new session ID that differs from the recorded session ID.

LoadRunner addresses this issue through correlation. Correlation saves the

changing values, in our case the session ID, to a parameter. When running

the emulation, the Vuser does not use the recorded value—instead, it uses

the new session ID, assigned to it by the server.

In this lesson you will observe how LoadRunner automatically solves the

issue of dynamic values.

In this lesson you will cover the following topics:

➤Preparing HP Tours for Playback Errors

➤How do I work with unique server values?

Preparing HP Tours for Playback Errors

To illustrate a common playback failure, you need to modify a setting in the

HP Tours application. This setting tells the HP Tours Web Server not to allow

duplicate session IDs.

1 Open HP Tours.

Choose Start > Programs >LoadRunner> Samples > Web > HP Web Tours

Application. A browser opens with the HP Tours opening page.

2 Change the server options.

Click the administration link on the HP Web Tours opening page. The

administration page opens.

Select the 3rd checkbox entitled: Set LOGIN form's action tag to an error

page. Scroll down to the bottom of the page and click Update.

Scroll down to the bottom of the page and click the Return to the Web

Tours Homepage link.

This setting tells the server not to allow duplicate session IDs.

3 Close the browser.

How do I work with unique server values?

In the modified configuration of HP Tours, the server assigns a unique

session ID to the Vuser. If you try to play back the script, it will fail.

To overcome this issue, you use VuGen to automatically detect the need to

correlate the session ID. After you run the script, VuGen prompts you to

scan the script for correlations.

Automatic Correlation

In this lesson, you scanned a script for correlations after recording the user

actions.

VuGen also provides a set of configurable correlation rules to handle

dynamic values during the recording session. For details on automatic

correlation, refer to the HP Virtual User Generator User’s Guide.

Most servers have clear syntax rules, or contexts, that they use when creating

links and referrals. If you are recording a session with a supported

application server, you can use VuGen’s built-in correlation rules, and

VuGen will detect and correlate the dynamic values during the recording

stage.

Where To Go From Here

Now that you are familiar with some of the common playback problems,

you can proceed to Lesson 6, “Preparing a Script for Load Testing

6

Preparing a Script for Load Testing

In the previous lessons, you verified that your script was an accurate

emulation of your application. You watched the playback in real time and

you verified that the Vuser performed a typical business process.

This, however, is true only for a single user emulation. Will the application

work with many users working simultaneously? If so, will the application

slow down to an unacceptable level?

The next step, therefore, is to prepare the script for a load test and set it up

to gather response time data. In this lesson you will learn about different

methods to enhance the script and to make it more effective for the load

testing process.

In this lesson you will cover the following topics:

➤How do I measure business processes?

➤How do I emulate multiple users?

➤How do I verify Web page content?

➤How can I produce debugging information?

➤Did my test succeed?

How do I measure business processes?

When preparing an application for deployment, you need to measure the

duration of specific business processes—how long does it take to log in,

book a flight, and so on. These business processes are normally made up of

one or more steps or actions within your script. In LoadRunner, you

designate a series of actions you want to measure by marking them as

transactions.

LoadRunner gathers information about the time it takes to perform a

transaction and displays the results in color-coded graphs and reports. You

use this information to see if the application meets the original

requirements.

You can manually insert a transaction anywhere in your script. The way to

mark a user step as a transaction is to place a start transaction marker before

the first step of the transaction and an end transaction marker after the last

step.

In this section you will insert a transaction in your script to measure the

amount of time it takes for the user to find and confirm a flight.

Open the script Basic_Tutorialwhich you created in Lesson 3. If it is still

open you can select the tab displaying its name, otherwise you can open it

from the File menu.

Notice how the Start Transaction and End Transaction markers have now

been added to the tree as new steps at the precise points where you inserted

them.

How do I emulate multiple users?

In your emulation, you tracked a user booking a flight and choosing an aisle

seat. In a real-life setting, however, different users will have varying

preferences. To improve your test, you therefore need to check if the

booking will work when users choose different seating preferences (aisle,

window, or none).

To accomplish this, you will parameterize the script. This means that you

take the recorded value, Aisle, and replace it with a parameter. You will place

values for the parameter in a parameter file. When you run the script, the

Vuser will take values from the parameter file (aisle, window, or none)

thereby emulating a true travel agency environment

5 Specify some sample values to vary the data.

Click Add Row. VuGen adds a row to the table. Replace the word Value with

Window.

Click Add Row. VuGen adds a row to the table. Replace the word Value with

None.

Note that the values are not case sensitive.

Keep the default settings in the Select column and File format sections of the

dialog box.

6 Define how the test will vary the data.

Keep the default setting that instructs VuGen to take sequential values for

each iteration—not random values.

Select next row: Sequential

Update value on: Each iteration

7 Click Close to close the Parameter Properties dialog box, and click OK to

close the Step Properties dialog box.

You have now created a parameter for the seating preference. When you run

the load test, the Vusers will use the parameter values instead of the

recorded value, Aisle.

When you run the script, the replay log shows the parameter substitution

that occurs for each iteration. You will see that for the first iteration, the

Vuser chose Aisle and for the second iteration, the Vuser chose Window.

How do I verify Web page content?

When running a test, you often need to verify if certain content is found on

the returned page. A content check verifies that expected information appears

on a Web page while the script is running. You can insert two types of

content checks: a text check and an image check.

➤Atext check checks that a text string appears on a Web page.

➤Animage check checks for an image on a Web page.

Looking for Text

In this section, you will add a text check that checks that the phrase "Find

Flight" appears on the reservations page in your script.

To insert a text check:

1 Open the Content Check Wizard.

Ensure that the Task pane is displayed (If not click the Task button). In the

task pane under the heading Enhancements, click Content Checks.

The Content Check wizard opens displaying thumbnails of each step in the

script.

Select the Page View tab in the right pane to display snapshots of the

thumbnails.

2 Select the page containing the text you want to check.

Click the fourth thumbnail entitled reservations.pl.

3 Select the text that you want to check.

Highlight the words Find Flight within the snapshot. With the words

selected, right click and select Add a Text Check (web-reg-find).

The Find Text dialog box opens displaying the text you selected in the

Search for specific Text box. Click OK.

4 View the new step.

In tree view (View > Tree View) you will notice that VuGen inserts a new

step, Service:Reg Find, into the script. This step registers the text check—

LoadRunner checks for the text after running the step. During replay,

VuGen will look for the text Find Flight and indicate in the replay log

whether or not it was found.

Looking for an Image

In this section, you will insert an image check to verify that the image fmagateway.

jpgappears on the page after the users log off.

To insert an image check:

1 Choose View > Tree View to return to tree view.

2 Select the page containing the image you want to check.

Select the Image: SignOff Button step. Select the Page View tab in the right

pane to view the step’s snapshot.

3 Insert an image check step.

Choose Insert > New Step. The Add Step dialog box opens

Expand Web Checks and select Image Check. Click OK. The Image Check

Properties dialog box opens.

4 Specify an image.

In the Specification tab, check the option Image server file name, and enter

the name of the image, fma-gateway.jpg, in the edit box.

Click OK. Note that VuGen inserts the Image Check step as a sub-step of the

Image: SignOff Button step.

5 Save the script.

During replay, VuGen will look for the image fma-gateway.jpg and indicate

in the replay log whether or not it was found.

How can I produce debugging information?

At certain points during the test run, you often need to send messages to the

output, indicating your location and other information. These output

messages will appear in both the replay log and in the Controller’s Output

window. You can send a standard output message or a message that

indicates that an error occurred.

Did my test succeed?

In this section, you will run the enhanced script and view the replay log for

text and image checks. You will view the text and image checks, the

transactions, and the parameterization.

By default, image checks are disabled during playback since they require

more memory. If you want to perform an image check, you need to enable

checks in the run-time settings.

1 Enable image checks.

Open the Run-Time settings (Vuser> Run-Time Settings) and select the

Internet Protocol: Preferences node. Select the Enable image and text check

option. Click OK to close the Run-Time Settings dialog box.

2 Run the script.

Click the Run button or choose Vuser> Run. VuGen begins running the

script, creating a replay log in the Output window. Wait for the script to

finish running.

3 Locate the text check.

Ensure that the output window is open (View > Output Window). Click in

theReplay Log tab and press Ctrl+F to open the Find dialog box. Search for

web_reg_find. The first instance says as follows:

Registering web_reg_find was successful.

This is not the actual text check—it only prepares VuGen to check for the

text after the form submission.

Search again (F3) for the next instance of web_reg_find. This instance

indicates:

Registered web_reg_find successful for “Text=Welcome” (count=1).

This verifies that the text was found. If someone changes the Web page and

removes the word Welcome, then in subsequent runs, the output will

indicate that the text was not found.