Exploratory Testing

Exploratory testing can be defined both as a method and a philosophy in software testing. Exploratory testing is a process in which learning, test design, and test execution are conducted simultaneously. In other words, the tester is not a passive implementer of the testing process but an active designer and developer of it.

In this approach, testers design tests based on information gathered while exploring the software rather than on pre-defined scenarios. Thus, the testing process has a dynamic flow rather than a static one. This dynamic structure also demonstrates a continuum between scripted tests and exploratory testing: fully predetermined tests lie at one end, while completely improvised free-style exploratory testing lies at the other.

Historical Background

During the 1980s, as software development practices became increasingly complex, testing processes were attempted to be made more measurable and repeatable by relying on specific plans, documented test scenarios, and reports. The dominant approach of this period was based on detailed pre-planning of tests and strict adherence to these plans. However, software development does not always proceed in a predictable manner, especially due to dynamic user requirements and rapid technological changes.

In this context, the concept of ad-hoc testing, meaning unplanned but flexible trial processes, established itself within testing practice. While ad-hoc testing fundamentally refers to random test attempts, it has often been regarded as a low-value method due to the absence of a systematic learning and feedback mechanism.

The concept of exploratory testing introduced a critical perspective to this scattered and unstructured approach. The term “exploratory testing” was systematically defined and introduced into the literature by software testing expert Cem Kaner in his classic work Testing Computer Software^【1】. According to Kaner’s approach, exploratory testing is not merely a random trial process; it is a cognitive activity in which learning, test design, and test execution are concurrently structured.

In the 1990s, the rapid transformation of the software industry, the widespread adoption of personal computers, and the dominance of short development cycles increased the importance of exploratory testing. Practices developed during this period, such as bug bash, drew attention as methods in which groups of testers conducted non-systematic tests during short sessions; exploratory testing formed the academic foundation of this culture.

On the other hand, the context-driven school approach argued that testing activities should not follow absolute rules but should be conducted in accordance with the dynamics of context, thereby transforming exploratory testing from merely a technique into a mindset. In this sense, exploratory testing has secured a lasting place in the discipline of software testing not as an alternative to traditional scripted tests but as a complementary paradigm.

Core Principles and Process Stages of Exploratory Testing

The fundamental philosophy of exploratory testing is based on the understanding that software testing should be conducted continuously, open to learning and feedback, independent of rigid plans and scenarios. Exploratory testing consists of four key stages:

1. Discovery: The initial stage of exploratory testing focuses on understanding the current state of the software. The tester identifies potential risk areas by observing both prior knowledge and the product’s instantaneous behavior. In this stage, elements such as the user interface, functionality, existing defects, and user behavior play a critical role.
2. Test Design: Information gathered during the discovery process is immediately converted into test design. At this point, traditional detailed test scenarios are replaced with flexible objectives. Commonly used charter structures define the purpose, scope, and boundaries of the test session.
3. Test Execution: Designed tests are executed on the spot. When the tester encounters new anomalies or unusual behaviors during execution, they immediately generate new test ideas. This is the fundamental mechanism that fuels the dynamic nature of exploratory testing.
4. Analysis and Reporting: Findings from test execution are analyzed. Defects are reported, potential gaps are identified, and the process is restarted if necessary. Thus, learning, design, and execution form a continuous feedback loop.

This cyclical structure transforms exploratory testing from a one-time activity into a continuous learning and quality control mechanism that progresses in parallel with the product lifecycle.

Types of Exploratory Testing

Exploratory testing can be applied in various forms depending on different scenarios and requirements. These types vary according to the purpose, scope, and implementation style of the testing process:

• Freestyle Exploratory Testing: The most free-form variant. The tester explores the software entirely based on their own observations and experience without any prior planning. This approach is often preferred for gaining familiarity with a new product or reviewing the work of other test engineers.
• Strategy-Based Exploratory Testing: A systematic exploratory process conducted by experienced test engineers using specific testing techniques such as decision table testing, boundary value analysis, equivalence partitioning, and error guessing. The strategy provides the tester with a comprehensive and structured framework.
• Scenario-Based Exploratory Testing: Conducted based on specific user scenarios. The tester analyzes how the system behaves end-to-end by following realistic usage paths. This is effective for verifying complex workflows.
• Charter-Based Exploratory Testing: The test session is defined by a clear charter. The charter specifies the goals, boundaries, and focus areas of the test. This structure is standard in Session-Based Testing applications.
• Time-Boxed Exploratory Testing: Has a defined time limit. The goal is to discover as many critical defects as possible within a specified time frame. This method is used in situations requiring speed and efficiency.
• Pair or Group-Based Exploratory Testing: A method in which multiple testers collaborate during the same session. Simultaneous observations bring together different perspectives and increase the capacity for defect discovery.

These types can also be combined in different contexts. For example, a session can be designed as both charter-based and time-boxed.

Session-Based Testing: Structured Exploration

One weakness of exploratory testing is that the process may lack documentation and traceability. Therefore, the Session-Based Test Management (SBTM) model, developed by James Bach, aims to preserve the flexibility of exploratory testing while enhancing its controllability.

In the SBTM approach, the testing process is divided into specific sessions. Each session:

• Contains a clearly defined charter.
• Is time-boxed (e.g., 90-minute blocks).
• Requires testers to systematically record findings during the session.
• Ends with the test manager or team lead receiving detailed feedback from the tester.

This structure transforms the freestyle flow inherent in exploratory testing into a planable and reportable format. SBTM ensures that testing activities are transparent, traceable, and evaluable, especially in large teams or high-risk projects.

For example, in a charter-based session, the tester might be given the task: “Experience the user login function across different devices and verify character limits and password reset scenarios.” This charter guides the tester but does not rigidly define the steps. Thus, the tester can dynamically shape the test flow in response to new situations encountered.

SBTM enables exploratory testing to be both creative and accountable, serving as a crucial bridge in modern software development processes such as Agile and DevOps.

Exploratory Testing in Agile, DevOps, and CI/CD Contexts

Modern software development paradigms emphasize principles of speed, flexibility, and feedback orientation at the core of Agile, DevOps, and Continuous Integration/Continuous Delivery (CI/CD) processes. In this context, exploratory testing plays a critical role as a complement to traditional scripted testing.

In Agile development cycles, short sprints and frequent changes prevent pre-defined test scenarios from always being sufficient. Since requirements and features can change rapidly, testers must adapt existing plans to quickly discover new risk areas. Exploratory testing directly addresses this need. Testers can identify critical flaws by testing newly emerged features during a sprint, non-standard workflows, or unforeseen combinations. This flexible structure also enables testing of complex user behaviors outside the scope of automation.

DevOps culture supports seamless integration and delivery between development and operations teams. In this environment, exploratory testing enters primarily at later stages as a complement to automation-focused regression tests. While automated tests verify known aspects of the software, exploratory testing uncovers unexpected behaviors, system integration errors, or details related to user experience.

In the context of CI/CD (Continuous Integration/Continuous Delivery), the advantage of exploratory testing is that testers can instantly explore the product and provide feedback even in projects with high release frequency. Thus, edge cases, data combinations, or real user behaviors that traditional scripted tests might miss can be tested.

Differences from Ad-Hoc Testing

Exploratory testing is often confused with the concept of ad-hoc testing in practice. However, as noted in the literature, these two approaches differ fundamentally in principle, process management, and outcomes.

Ad-hoc testing, derived from Latin meaning “for this purpose,” typically refers to random and unplanned testing activities. In this method, the tester applies only the tests that come to mind without adhering to any specific plan or methodology. It is often performed once, with no learning objective or systematic knowledge generation.

In contrast, exploratory testing goes beyond randomness by incorporating a systematic process of learning, observation, and feedback. Here, the tester uses each new finding to refine the design of the next step, thereby enhancing the depth and scope of testing. Ad-hoc testing is usually performed quickly, but its repeatability is poor and documentation is often absent. In exploratory testing, sessions are guided by charter documents, and notes and reports are created. This is a critical difference in terms of traceability and repeatability.

In this context, exploratory testing is not a random activity like ad-hoc testing but a planned exploration strategy.

Key Practices

According to the literature, some key practices enhance the effectiveness of exploratory testing:

• Use of Clear Charters: Each session should have a clear, concise, and specific mission (charter). The charter defines what the tester should test and what to focus on discovering.
• Time-Boxed Sessions: Sessions should be limited to specific time frames to maintain tester focus. This approach prevents inefficient scattered testing.
• Note-Taking and Documentation: Traceability should be ensured through passive tools such as screenshots, voice notes, or screen recordings throughout the process. This strengthens the accuracy and repeatability of test results.
• Feedback Loop: Findings from test sessions should be regularly reported, shared with the test lead or manager, and used to optimize future sessions.
• Group Work: Pair or group test sessions combine different perspectives and increase the rate of defect discovery.
• Leveraging Tools: Exploratory testing sessions should be recorded using test management tools, and findings should be converted into scripted tests when appropriate to enable reuse.