What do you understand by black box testing?

 Black Box Testing:-Black Box Testing is also called behavioral testing, focuses on the functional requirements of the software. It enables the software engineer to derive sets of input conditions that will fully exercise all functional requirements for a program. It is a complementary approach that is likely to uncover a different class of errors than white box testing.

Black Box Testing attempts to find errors in the following categories:-

1)                     Incorrect or missing functions.

2)                     Interface errors.

3)                     Errors in data structures or external database access.

4)                     Behavior or performance errors.

5)                     Initialization and termination errors.

Black Box Testing tends to be applied during later stages of testing because black box testing purposely disregards control structures; attention is focused on the information domain.

Equivalence class:-It represents a set of valid or invalid states for input conditions. An input condition is either a specific numeric value, a range of values, a set of related values, or a Boolean condition. Equivalence class may be defined according to the following guidelines:-

1)     If an input condition specifies a range, one valid and two invalid equivalence classes are defined.

2)     If an input condition requires a specific value, one valid and two invalid equivalence classes are defined.

3)     If an input condition specifies a member of a set, one valid and one invalid equivalence class are defined.

4)     If an input condition is Boolean, one valid and one invalid class are defined.

Equivalence Partitioning:-Equivalence partitioning is black box testing method that divides the input domain of a program into classes of data from which test cases can be derived. An ideal test case single-handedly uncovers a class of errors that might otherwise require many cases to be executed before the general error is observed. Equivalence partitioning strives to define test case that uncovers classes of errors, thereby reducing the total number of test case that must be developed.