Answer.

Test cases are pre-prepared scenarios with clearly defined steps, input, and expected results. Exploratory testing is built on-site: the tester generates checks while learning the product, using their expertise and intuition. Historically, test cases dominated first, but as systems became more complex and the volume of manual testing increased, exploratory testing began to complement formal approaches.

Problem

Blindly following only one type of testing limits the tester's ingenuity and may leave the product with undetected bugs that are not described in the cases.

Solution

Use both approaches in a balanced way: test cases for regression and critical functionality, exploratory for new, not yet fully formalized areas and under time constraints.

Key Features:

Test cases guarantee repeatability and comparable results
Exploratory testing increases the chance of finding non-standard and tricky bugs
Both approaches should go together

Tricky Questions.

Can only test cases be used for 100% coverage?

No. Even the most detailed set of cases does not cover unexpected user behavior or non-standard bugs.

Does exploratory testing require prior preparation?

Yes. It is essential to understand the functionality, study the requirements, and grasp the business logic before freely exploring the product.

Is a bug report mandatory after exploratory testing?

Yes. Any defect found should be documented as thoroughly as a bug from a formal scenario; otherwise, it is difficult to reproduce and fix.

Typical Mistakes and Anti-Patterns

Neglecting one of the approaches
Lack of documentation for found bugs during exploratory testing
Lack of knowledge about the product's functionality before starting the exploratory session

Real-Life Example

Negative Case

The team covered the release only with formal test cases. One tester executed them strictly according to instructions without checking "adjacent" cases, resulting in a bug being missed that occurs under a specific sequence of actions not anticipated in advance.

Pros:

Fast and easy report automation

Cons:

Insufficient depth of checking
Lack of flexibility

Positive Case

The tester allocated an hour for exploratory testing after going through key test cases and found a bug that reproduces only when changing the time on the device during the application’s operation.