Both Boundary Value Analysis and Equivalence Partitioning are test case design strategies used in Black box testing
1) Boundary Value Analysis:- It is a technique for Test Date selection. This technique is used to find errors at extreme points rather than finding those which exists in center. By using Boundary value there is maximum possibility of finding bugs in minimum time.
Suppose that a password length must be between 5 to 20 then instead of testing with whole data we will test with
Upper boundary value 19, 21
Lower boundary value 4, 6
On boundary value 5, 20
2) Equivalence Partitioning:- In this technique we divide test data into different equivalence data classes i.e. 'Valid' and 'Invalid'. It is generally used to reduce the number of test cases to a finite testable test cases covering maximum possibilities. It is a process of taking all possible test cases and placing them to classes, taking one test value from each class.
Suppose that an application accepts values between 10 to 100 then we can divide the test data into two classes i.e. Valid and Invalid as
Invalid test data 9, 101
Valid test data 15, 80