What is exploratory testing?

Exploratory testing is a simultaneous test design, execution, and learning activity where the tester explores the application without predefined test cases, using their intelligence, creativity, and domain knowledge to discover defects. Contrast with scripted testing (following predefined test scripts step-by-step). James Bach describes it as "simultaneous learning, test design, and test execution." Benefits: (1) Finds defects that scripted tests miss — a human tester notices unexpected behavior. (2) Adapts dynamically based on what's discovered. (3) Efficient — no script writing overhead. (4) Effective for newly developed features and complex interactions. Techniques: Session-based testing: time-boxed (60-90 min) focused exploration with a charter (mission). Pair testing: two testers exploring together. Personas: exploring as specific user types. Exploratory testing complements automated testing — automation handles known behaviors; exploration discovers the unknown.