Simultaneous test design and execution against an application is called exploratory testing. In this testing, the tester uses his domain knowledge and testing experience to predict where and under what conditions the system might behave unexpectedly.

Exploratory testing is an approach to software testing that is often informal and unscripted. In exploratory testing, testers are given the freedom to dynamically explore the software application, learning about it as they test and making decisions about what to test and how to test it in real-time.

Key characteristics of exploratory testing include:

No predefined test cases: Unlike traditional testing methods, exploratory testing doesn’t rely on predefined test cases. Testers create and execute tests on the fly based on their understanding of the application.
Learning while testing: Testers learn about the application’s behavior, features, and potential issues as they perform testing. This learning process helps identify additional test scenarios and areas to focus on.
Adaptability: Testers can adapt their testing based on the feedback and observations made during the testing process. This adaptability allows them to explore areas that may not have been initially considered.
Tester’s expertise: Exploratory testing often relies on the skills and experience of the tester. Testers use their domain knowledge, intuition, and creativity to uncover defects and vulnerabilities.
Real-time feedback: Exploratory testing provides immediate feedback to the development team. Testers can quickly report issues as they are discovered, allowing for faster resolution.

It’s important to note that while exploratory testing is less structured than scripted testing, it doesn’t mean it lacks discipline. Skilled testers employ a systematic and focused approach to uncover potential issues efficiently. Exploratory testing is particularly useful in situations where the requirements are unclear or rapidly changing, and creativity and intuition are valuable assets in finding defects.