Exploratory testing

"He is a skilled tester, hence he might be a good exploratory tester."

Exploratory software testing is a powerful and fun approach to testing .The plainest definition of exploratory testing is concurrent learning, design, execution and recording.Exploratory tests, unlike scripted tests, are not defined in advance and carried out precisely according to plan.

Exploratory testing is known as informal testing but it is formally informal method; analyze the outputs and give possible inputs to get that particular output. There are situations where exploratory testing is done without requirements document, rather test cases are written while exploratory testing and transformed into requirements document.

Exploratory testing is an approach that is extra suitable if requirements and specifications are incomplete, or if there is lack of time. This doesn’t mean that it cannot be used otherwise. It compliments or augment other; more formal testing. The main advantage of exploratory testing is that less preparation is needed, and finds serious bugs quickly which are not surfaced by the formal test cases. It is also known as “on the fly”.

The method can serve as a check on the test process, to help ensure that the most serious defects are found. It is common to perform a combination of exploratory and scripted testing where the choice is based on risk.

An example of exploratory testing in practice is Microsoft’s verification of windows compatibility.

Drawbacks:

1. Disadvantages are that the tests can't be reviewed in advance (and by that prevent errors in code and test cases), and that it can be difficult to show exactly which tests have been run.

2. When repeating exploratory tests, they will not be performed in the exact same manner, which can be an advantage if it is important to find new errors; or a disadvantage if it is more important to know that exact things are functional.

3. Exploratory tests are not the suitable candidates for automation.
While all exploratory testing is based on the knowledge of the tester.

The knowledge that the exploratory tester already has varies from person to person, just as with any sort of knowledge. Example, some testers have a great deal of familiarity with the application or type of application that they’re testing. Some testers base their tests on a sense of risk and their knowledge of how products can fail.

Bug taxonomies help the new and in experienced testers in doing exploratory testing efficiently.

Sources:

James Bach satisfice.com
Ashwin palaparthi
Cemkaner