Mainframe Testing Tutorial for Beginners

We will learn about Mainframe testing in this section, which is used to test software, applications, and services produced on Mainframe Systems.

We will also learn about mainframe attributes, mainframe testing types, how to perform it, the various challenges and troubleshooting while performing mainframe testing, various commands used in mainframe testing, some common issues encountered during mainframe testing, and Mainframe Automation Testing Tools.

We'll learn about the Mainframe before diving into the concept of Mainframe testing.

What is a Mainframe?

The mainframe is a multi-user computer system with great performance and speed. The mainframe is the most secure, scalable, and dependable machine system available.

In other words, these systems are utilized for larger-scale computing, which requires a high level of availability and security. Mainframe systems are commonly employed in industries such as retail, insurance, finance, and other essential areas where large amounts of data must be processed several times.

With the help of the following aspects, we can accomplish millions of instructions per second [up to 569,632 MIPS] −

  • Maximum input/output bandwidth −If we have excessive input and output bandwidth, the links between drives and processors have a few choke points.

  • Reliability − Mainframes frequently consent to graceful degradation and service while the system is running.

  • Reliable single-thread performance − This is critical for practical database operations.

  • Maximum Input/Output Connectivity − A mainframe's maximum input/output connectivity indicates that it excels at delivering large disc farms.

We've arrived at our major point of discussion on mainframe testing now that we've grasped the mainframe concept.

What is Mainframe Testing?

The process of evaluating software applications and services based on mainframe systems is known as mainframe testing. The goal of mainframe testing is to assure the performance, reliability, and quality of a software program or service through verification and validation procedures, as well as to determine whether it is ready to deploy.

When performing Mainframe testing, the tester just needs to be familiar with the CICS screen navigations. They're made to order for special purposes. The tester does not have to worry about the emulator being set up on the system if modifications are made to the code in COBOL, JCL, or other languages. Changes that work on one terminal emulator will also work on other terminal emulators.

  • The test cases built using requirements are used to test the Mainframe application (also known as job batch).

  • Mainframe Typically, testing is done on the deployed code with multiple data combinations entered into the input file.

  • Using a terminal emulator, you can access applications that operate on the mainframe. On the client system, the emulator is the only piece of software that has to be installed.

Attributes of the Mainframe

Virtual Storage

  • It's a technology that allows a processor to simulate primary storage that's greater than the real thing.

  • It's a method for efficiently storing and executing various-sized tasks by utilizing memory.

  • It makes use of disc storage as a supplement to real storage.


  • At the same time, the computer runs multiple programs. However, only one program can control the CPU at any given time.

  • It's a feature that allows you to make the most of your computer's processing power.

Batch Processing

  • It is a method of completing any task in discrete chunks known as jobs.

  • One or more programs may be executed in sequential order as a result of a job.

  • The job scheduler determines the sequence in which the jobs should be completed. Jobs are scheduled according to priority and class to maximize average throughput.

  • JCL provides the necessary information for batch processing (JOB CONTROL LANGUAGE). JCL describes the batch task, including the programs, data, and resources that are required.


Each user in a time-sharing system has access to the system via a terminal device. Instead of submitting jobs that will be executed later, the user submits commands that will be processed right now.

As a result, this is referred to as "Interactive Processing." It allows the user to communicate with the computer directly.

"Foreground Processing" refers to time-share processing, while "Background Processing" refers to batch task processing.


Simultaneous Peripheral Operations Online (SPOOLing) is an acronym for Simultaneous Peripheral Operations Online.

The output of a program/application is stored in the SPOOL device. The spooled output is sent to devices such as a printer (if needed).

It's a feature that takes advantage of buffering to make the most of the output devices.

Where does the mainframe testing take place?

In most cases, mainframe testing is performed on deployed code using numerous data permutations in the input file. In other words, the Mainframe Applications must be thoroughly tested prior to going into production.

The batch task, also known as the mainframe application, is tested in opposition to the test cases produced with specifications.

The terminal emulator can be used to retrieve software or applications that run on the mainframe.

We'll look at the many characteristics of mainframe testing after we've grasped the basics of mainframe testing.

How to Test a Mainframe?

Manually or with the help of automation tools like QTP, REXX, and IBM application performance analyzer, mainframe testing can be done in two ways. In most cases, however, we will perform Mainframe testing manually.

We must follow the steps below to perform mainframe testing −

Step 1: Make a plan

To begin, the business or development team creates test plans that include the Business requirement document, System requirement document, other project documents, and inputs. It also determines how a certain item or process will be altered within the release cycle.

Meanwhile, the testing team will work with the development and project management teams to generate test scenarios and test cases ahead of time.

Step 2: Make a schedule

The requirement document will be handed over to the development and testing teams once it has been properly prepared. In addition, the testing schedule should be written in conjunction with the project delivery plan, which must be precise.

Step 3: Deliverables

They will review the deliverables after obtaining the document. And the deliverables should be well-described without any ambiguity, and they should meet the scope of the test objectives.

Step 4: Put it into action

Following that, the implementation should proceed according to the plan and deliverables.

In most cases, the modified requirement in a release will directly affect 15-25 percent of the application. The remaining 60-75 percent of the release will rely on out-of-the-box features such as application and process testing.

As a result, we must test the Mainframe application in two different ways −

  • Testing Requirements
  • Testing Integration

Testing Requirements: We will test the application for the features or modifications specified in the requirement document.

Testing Integration: Regression The focus of this testing activity is on testing. We'll also test the entire process, as well as any other applications that receive or send data to the valuable app.

Step 5: Reporting

We'll then share the test results with the development team on a regular basis that. To preserve consistency, the testing team should communicate with the development team to make immediate changes in critical situations.

Mainframe Testing Methodology

Consider the following scenario: A member enrollment tool is available at the XYZ insurance business. It gathers information from both the online and offline member enrolling screens. As previously said, there are two methods for Mainframe testing: online testing and batch testing.

Online Testing − The member enrollment screen is used for online testing. The database is checked using data input through the displays, just like a web page.

Offline Enrolment − Paper enrollment or enrollment on a third-party website are both examples of offline enrolment. Batch jobs will be used to insert offline data (also known as a batch) into the company database. An input flat file is created in the necessary data format and fed into a batch job sequence. As a result, we can use the following method to test mainframe applications.

  • The first job in the batch job line validates the information entered. Consider special characters, alphabets in number-only fields, and so on.

  • The second task verifies that data is consistently based on business conditions. For example, dependent data, member zip code (which is not available for service by the enrolled plan), and so on should not be included in a child enrollment.

  • The third job is to change the data so that it can be entered into the database in a usable way. For example, appending the date of entry, deleting the plan name (the database will only keep the plan ID and insurance plan name), and so on.

  • The data is loaded into the database by the fourth job.

Batch Job Testing − This procedure is tested in two phases −

  • first, each job is validated separately, and then

  • the integration between the tasks is validated by supplying an input flat file to the first job and validating the database. (Because of the added caution, intermediate results must be confirmed.)


  • Starting with requirement collection, test design, test execution, and result reporting, mainframe testing is similar to any other testing technique.

  • In order to properly test the application, the tester should attend design meetings organized by the development and business teams.

  • The tester must become familiar with a variety of mainframe test functions. Before the test cycle begins, you'll need to learn how to navigate the screen, create files and PDS, and save test results, among other things.

  • Testing mainframe applications take a long time. For test design, data setup, and execution, a clear test schedule should be followed.

  • Batch and online testing should be carried out effectively, with no feature not specified in the Requirement document being overlooked, and no Test Case should be overlooked.