BVA :

Boundary Value Analysis :

1.It is a Black Box Technique
2.Here input values for boundaries of input domain are 
tested.
3.Here valid and invalid both values are considered.

Example :
For a login page SRS is

UserId should be within 15-50 characters
so valid boundaries are 15-50
invalid boundaries are <15 or >50 i.e; 14 or 51
If A(Valid)=15/50 thenA1(Invalid)=14/51
For Invalid Boundaries always considered like this way (A-
1) or (A+1) 

Adv:
>Very good at exposing potential input problems
>very clear guide-lines on determining test cases
>Very small set of inputs are generated

Disadv:
>Doesn't cover all set of inputs.
>doesn't combine all possible combination

ECP  

Equivalence Class Partitioning :

1.As the name suggests that the data is divided into such a 
way that same class will give same type of input.Like 
Class1 is a combination of Valid inputs and Class2 is a 
combination of Invalid inputs.

Disadv :
>Heuristic based method.
>Limited focus.
>No guide lines for choosing input.

These two menthods are useful to minimize the test cases. 
These two methods are looking very simillar

In BVA(Boundary Value Analysis) we can check the the 
boundaries values min-1, min, middle value(optional), max, 
max+1
For example: If the boundary value for a field is between 1 
to 98 , we can check with the values  0,1, any of the value 
between 1 to 98 , 98 and 99


please let me know if i'm not correct


but in Equivalece Class Partioning we should check the 
condition with different values from three partitions like 
we should take some values in the positive partition and  
take some values from negative partitions. For example take 
the above example here the positive partition is the range 
beteween 1 to 98, the negative partitions are o to -97 and 
99 to 196. 

see in the BVA we are not checking with the minus values 
like -1, -2, -3 we can't say it can't take minus values and 
also we are not checking with the three digit numbers in 
the BVA, but here we have scope to check the three digit 
values also as well

Boundary value analysis and equilance class partioning are 
the testcase design techniques.

EQUILANCE CLASS PARTIONING:
        ECP is a method for deriving the test cases.in this 
method idetified that each member of the class causes the 
same kind of proceesing and output to occur.Based and the 
characteristics classes are formed in valid and invalid 
classes.

BOUNDARY VALUE ANALYSIS:
      Testing at the two boundaries.

0-40:F
41-50:D

 -1,0,1,39,40,41:F
40,41,42,49,50,51:D