Test Design Techniques

Test design techniques have been taught for decades - but very few testers apply them in practice. The problem: too many techniques, too little real competence, too little time for transfer. Instead, those who master five central techniques from four groups cover 90 percent of all test situations - from processes and conditions to data and appearance. The decisive factor is not the number of methods learned, but the ability to use the right technique at the right time.

Podcast Episode: Test Design Techniques

In this episode, I talk to Rik Marselis about test design techniques. Rik, who has been teaching these techniques for almost 25 years, shared his thoughts on why so many testers underutilize them. He explains why these methods are so important, especially if you want to prove the quality of IT systems. We also talk about how test design techniques can be categorized into four main types and why it’s crucial for testers to know at least one or two techniques from each group. Rik shares his three favorite techniques and gives tips on how to choose the right technique for a particular problem.

“So we make them aware of the fact that basically there are four things relevant for selecting a test design technique: the kind of testing problem, the quality characteristic, the risk level, and the skills of the people involved.” - Rik Marselis

Rik Marselis is a senior quality consultant at Sogeti in the Netherlands. He is a respected speaker, trainer, author, consultant and coach who has helped many organizations and individuals improve their quality development and testing practices by providing tools and checklists, practical support and deep discussions. His presentations are always appreciated for their vividness and his use of practical examples with humorous comparisons.

Highlights der Episode

• Testers learn 15-20 test design techniques, but apply almost none - too much theory, too little practice.
• Four groups are enough: process-, state-, data- and appearance-based techniques - one technique per group is enough.
• Decision tables fail without a template - the right structure suddenly makes complex techniques trainable.
• Path testing is underestimated: business processes need path coverage, not state machines - ISTQB teaches the wrong thing.
• Developers only test the happy path - equivalence partitioning forces them to also test error cases.

Why test design techniques are often overlooked and how to use them effectively

Why are test design techniques not frequently used?

Test design techniques provide a structured basis for testing IT systems, but their use is still not widespread - even though some of them have been around for a long time. One of the main reasons for this is that testers often find it difficult to transfer them into practice. According to ISTQB and TMAP, the combination of experience-based methods such as exploratory testing and structured test design techniques provides comprehensive coverage and increases confidence in the functionality of a system.

The challenge of diversity

Another stumbling block is the large number of available test design techniques. According to research findings, there are actually around 25 to 30 techniques. This variety can overwhelm testers and make selection difficult. However, focusing on five central techniques offers a practicable solution: equivalence class formation, limit value analysis, path testing, decision tables and syntactic testing. In addition, exploratory testing plays an important role as an experience-based method.

Categorization of test design techniques

Test design techniques can be divided into four main categories: process-oriented techniques (e.g. path testing), condition-oriented techniques (e.g. decision tables), data-oriented techniques (e.g. equivalence class formation) and appearance-oriented techniques (e.g. syntactic testing). Understanding these categories makes it easier to select suitable methods. The use of suitable methods is crucial for different problems - for example, a condition-oriented method would be ineffective for a data-oriented problem. If you have mastered at least one or two methods from each category, you have a versatile tool set at your disposal.

Practical application of the techniques

Implementing these methods in day-to-day work can be difficult without suitable tools. Some methods, such as limit value analysis, are so intuitive that they are often applied unconsciously. More complex approaches such as decision tables, on the other hand, benefit from standardized templates, for example from TMAP. Such templates facilitate correct and efficient application and lower the inhibition threshold when using them.

Training courses and practical examples

An effective introduction to test design methods requires training based on real examples. Applying these methods to specific processes, such as those carried out by business analysts, increases understanding and acceptance. This practical approach shows the direct benefit of the methods in the respective work context and facilitates their use.

Fazit

Test design techniques are an indispensable tool for high-quality and comprehensive software testing. By focusing on key methods, understanding the categories and using templates and training, testers can efficiently integrate these techniques into their daily work. This leads to a more systematic and well-founded quality assurance of IT systems.