4 keys to a top-down testing strategy

level components

Identify errors in the interaction between system components at different levels. Integration testing checks if the interaction between system components is compliant with all requirements. At different companies, different roles may be responsible for writing and running the integration tests. It all depends on each company’s hiring policy, as well as the engagement model for software delivery and the developer-to-tester ratio in the team.

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After each top down approach in testing has been developed and tested individually, they can be integrated into the larger system. Next, the system is broken down into smaller, more manageable components or modules. For example, in the Dodd Frank Act Stress Test there’s a 9 Quarter projection which requires banks to run multiple supervisory scenarios to evolve portfolios over the projected horizon. This is imposed on balance sheet and income statement items as well as market and credit risk specific calculations that have underlying trading portfolios with high complexity. However, if we’re just evolving balance sheet line items there are cases where a top-down model can be very useful for projections such as the Real Estate loan example described earlier.

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Higher level modules are tested & integrated first and then lower level modules are tested & integrated. This test ensures that the integrated units work properly as a unit. However, there are two approaches to incremental integration testing. You can execute an incremental integration test by following a top down or bottom up approach. Since process-related communication flows top to bottom in top-down companies, it’s easy for individuals and groups to become siloed and eventually feel isolated.

  • These elements are then linked together to form larger subsystems, which then in turn are linked, sometimes in many levels, until a complete top-level system is formed.
  • These stubs act as s temporary replacement for a called module and give same result or output as actual product gives.
  • It is an integration testing technique used to imitate the lower-level modules that are not yet integrated.
  • If a system is to be built from an existing system, this approach is more suitable as it starts from some existing modules.
  • The only thing we need to remember here is to draw the diagram with logical modules only, i.e., the modules that will get connected in the application.

If any bugs were in the integrated software and required disintegrating the modules to develop and test again, it could result in a lot of time consumption. However, if the requirement is to test major defects in the integrated system first, the tester might not face any problems. This restriction makes us develop a dummy code that will act on behalf of the original module without actually calling it during testing.

What is Bottom-Up Approach?

These compartmentalized sub-routines eventually will perform actions so simple they can be easily and concisely coded. When all the various sub-routines have been coded the program is ready for testing. By defining how the application comes together at a high level, lower level work can be self-contained. By defining how the lower level abstractions are expected to integrate into higher level ones, interfaces become clearly defined.

The most popular, and worth https://1investing.in/ing out, are FitNesse and Validata ATS. Top-down method, the main feature is that testing begins with the higher-level components of the software and gradually progresses towards the lower-level ones. This approach is especially advantageous when some system parts have priority over others.

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Mainly implemented in structure or procedure oriented programming languages. This integration testing is done on applications developed using object-oriented languages. While following this upward testing direction, drivers are eliminated as main modules get developed completely. In the bottom up testing technique, testing is done from the submodule to the main module.

Key difference between top-down and bottom-up incremental integration testing

High-level modules are also known as main modules, whereas low-level modules are referred to as submodules. When leaders understand the value of proper software testing, they can help teams deliver better software releases. IT leaders can also more readily recognize new opportunities to improve testing approaches with technologies such as automation. Also, for automation to be successful, design and organization of tests are essential. One way to do this can be action-based testing, a keyword-driven, modular approach to test design and automation. Bottom-up Integration Testing is a strategy in which the lower level modules are tested first.

software module

With greater visibility into test cases, teams can structure their tests better, in turn leading to better coverage and easier maintenance of the automation. If you involve senior leaders in the testing process from the beginning, you can overcome many of these problems. While those leaders won’t be doing the manual work, they should understand at a basic level what it takes to test and deliver great software.

A driver creates necessary ‘Inputs’ required for the Unit and then invokes the Unit. A software application is made up of a number of ‘Units’, where output of one ‘Unit’ goes as an ‘Input’ of another Unit. A ‘Sales Order Printing’ program takes a ‘Sales Order’ as an input, which is actually an output of ‘Sales Order Creation’ program.

You see, I’ve found that defining the project is often one of the most fundamental steps you need to do if you want to make sure you don’t end up staring at the wall and procrastinating. It really doesn’t matter if we’re talking about programming or writing your dissertation (if you don’t want to use a dissertation writing service, anyway). Well, obviously having code that the computer can understand, because otherwise it’s not working problem, but you get the idea. You can’t change the code that you can’t understand, while code the computer can’t yet understand is just a few steps away from a fully functioning program. While not as popular as it once was, top-down programming still provides structure, hierarchy, and organization to developers who might be adrift otherwise.


This approach has advantages that make it a great fit for creative teams and industries where collaboration is key, like software development, product design, and more. This type of testing method deals with how lower-level modules are tested with higher-level modules until all the modules have been tested successfully. Even though integration testing is a challenge in CI environments, the struggles are worth it.

Same as for top-down testing, stubs and drivers take the place of lacking submodules to perform as called and calling programs. In any case, even with a well-designed, logical strategy for software integration testing in place, it’s still only possible to simulate the work of receiving modules and achieve the most realistic test results. This means that you won’t know if there are any interaction issues in the lower-level modules. Testing goes beyond just checking if the system modules function at all.

  • In this Bottom Up approach the lower level modules are tested first after lower level modules the higher level modules are tested.
  • If the invoked submodule hasn’t been developed yet, stubs are used for temporarily simulating that submodule.
  • This technique follows the control flow or architectural structure to test it from top to bottom.
  • Integration testing is one of the critical phases of scrutinizing software after or during its development.

Building blocks are an example of bottom-up design because the parts are first created and then assembled without regard to how the parts will work in the assembly. The implementation depends on the programming language and platform. It is generally used with documentation of module and debugging code. Bottom-Up Approach is one in which the smaller problems are solved, and then these solved problems are integrated to find the solution to a bigger problem. For example, if the movefighter method has not been written yet, a stub such as the one below might be used temporarily – which moves any player to position 1. A ‘Stub’ takes place of such subordinate unit during the Unit Testing.

However, now let’s say we have three products Equity, Equity Option and a Bond. Very quickly we have what I like to refer to as « Portfolio Mechanics ». FRBR models the bibliographic data using entities to represent data that are distinctly identified. It also uses relationships to establish the associations between the different entities.


Face and content validity are important aspects of health-state instrument development, yet they have seldom been appraised. An appropriate selection of health items can be enhanced by acknowledging the importance of clinical insight and patient participation to the development process. Requirements tracing, a process of documenting the links between the requirements and the work products developed to implement and verify those requirements. Requirement Traceability Matrix is a document which records the mapping between the high-level requirements and the test cases in the form of a table. The RTM captures all requirements and their traceability in a single document delivered at the conclusion of the life cycle. If the system consists of a greater number of sub-modules, this approach becomes time-consuming and complex.

Examples of bottom-up programs include many small NGOs set up to improve local access to healthcare. With structuring information interfaces in our neurological processes for procedural learning. These processes where proven effective to work in our interface design. However, Although both top-down principles were effective in guiding interface design, they were not sufficient. They can be combined with iterative bottom-up methods to produce usable interfaces (Zacks & Tversky, 2003). Bottom-up emphasizes coding and early testing, which can begin as soon as the first module has been specified.