Test approaches applied

The many aspects of creating tests and exploring a test object

Quality engineering consists of many different tasks for a DevOps team. A part of quality engineering focuses on building quality into the IT system. Another part of quality engineering assesses the quality of the delivered IT system.

The building block "Test design", focuses on the creation and execution of tests, such as specifying test cases and performing exploratory tests.

Creating some tests and executing them may sound easy. But structured testing requires careful consideration of what to test and how to test it. We use the term "test design" for the complex whole of these activities, even though in some approaches to testing there is no actual up-front design involved.

Test design can be as simple as hitting some keys unprepared and see if a system works at all (ad hoc testing). And it can be as sophisticated as identifying test situations, assuring coverage by designing test cases, automating these in a test script and executing the script to automatically create a test report.

Both unstructured testing and structured testing will contribute to establishing confidence that the IT-solution will be able to deliver the pursued value. The preferred approach very much depends on the situation, especially with the quality risks involved. We do however already want to emphasize that a structured approach to testing is generally better than unstructured testing.

Two distinct ways of preparing and performing tests

The test strategy defines the intensity of (specific parts of) the testing of the test object. This test intensity is achieved by applying test approaches and test design techniques.

Definition

A test approach is a way of working for designing and executing tests. There are two groups of test approaches: experience-based testing and coverage-based testing.

The test approach is the approach that someone takes when creating test cases. To prepare and perform tests, we distinguish two overall approaches:

Selecting and combining approaches and techniques

 

Experience-based testing

Experience-based testing is a group of test approaches that are based on the skills, intuition and experience of the tester. These approaches leave the tester free to design test cases in advance or to create them on the spot during the test execution, mostly testers will do both.

Definition

Experience-based testing is testing based on the experience, skill and intuition of the tester(s).

Within experience-based testing we identify various approaches. In the past we used to call them techniques but in our opinion a technique follows strict rules to design one or more test cases. The experience-based approaches by definition do not follow strict rules, instead they rely on skill, intuition and experience. Therefore, we call them approaches.

Experience-based testing approaches work iteratively

Every experience-based approach basically follows the flow as depicted the figure. The experience-based approaches are described in section Experience-based testing.

Coverage-based testing

Coverage-based testing aims to demonstrate a specific type of coverage of one or another aspect of an IT system. This can be done by designing test situations and test cases with test design techniques.

Coherence of relevant terms in structured test design

Definition

Coverage-based testing is a structured approach to testing that aims to demonstrate a specific type of coverage by applying one or more test design techniques.

Below figure describes the coherence of the relevant terms in structured test design.

In coverage-based testing we always have a structured way of detailing information from one level to another. The starting point of testing is the value that is pursued by the stakeholders. In the development process this value is translated into requirements and specifications. Based on both value and requirement specifications, the quality risks are identified. Using the requirements specifications and the quality risks, the test situations are identified. Using test design techniques, these test situations can be covered at the right level by creating test cases and accompanying test data. Finally, the test cases are combined in test scenarios and (optionally) automated in test scripts. When these test scenarios and test scripts are executed, the actual outcomes are compared with the expected outcomes. There are two possibilities:

  • If the outcomes match, this means the test has passed, the quality risk is covered, the requirement implemented and the stakeholders can be informed through the reports that this part of the pursued value seems to be achievable.
  • If the expected and actual outcomes do not match, this means the test failed and a quality risk has materialized, and the requirement is not yet implemented. Therefore, the stakeholders must be informed through the reports that this part of the pursued value is not yet achievable.

More detailed explanation can be found in the Building Block "Coverage-based testing". Here we start with the test design entities, followed by the coverage groups and an overview of test design techniques.

Reporting based on test results

Based on the results of both experience-based and coverage-based testing, information is provided (orally, through documents or in a real-time dashboard) to the stakeholders.

The debriefing information from experience-based tests is integrated with the information from the coverage-based tests and this together

There are of course multiple stakeholders in any given situation; the reporting needs to be tailored to their needs. In general, we propose three levels of reporting:

  • Detailed reporting for the members of the DevOps team and their direct contacts.
  • Overview reporting for people that look upon the test object from a business perspective such as the product owner and users.
  • High-level reporting for the stakeholders that are more distant to the team's activities such as high-level managers.

These levels of reporting are shown in the below figure, which also shows the relation with the test design entities.

Different levels of reporting for different groups of stakeholders

More details on reporting in a DevOps situation can be found in "Reporting & alerting".

Always combine experience- and coverage-based testing

The use of experience-based and coverage-based approaches is not a matter of one or the other. It is always wise to combine both test approaches, sometimes more experience-based, sometimes more coverage-based, but never exclusively one or the other.

Always combine experience-based and coverage-based approaches

When the quality risks are relatively low, testers may decide to mainly apply experience-based testing. Still, if the tester for example encounters a boundary value during exploratory testing, it is very wise to apply boundary value analysis on the spot and make a test for each boundary value.

On the other hand, when the quality risk level (or any other good reason) is such that coverage-based testing is the main approach, then some experience-based testing is still a good thing to do. For example, investigating unexpected outcomes, or giving an important stakeholder a chance to see for themselves that the system actually works (because nothing adds so much to confidence as seeing it with their own eyes).

The choice for the division of testing over experience-based and coverage-based may also depend on the type of IT system that is tested. With a system that contains Artificial Intelligence, it is difficult to make an exact expectation of the outcome. Therefore, more experience-based testing may be a good choice. An IT system that relies heavily on calculations (for example, a financial application), may need very precise test cases and therefore will use more coverage-based testing.