3. Forms of Equivalence Class Testing
Normal
• only equivalence classes are valid and invalid input values
• emphasis is on "single failures"
• works well when variables have a valid range
• test cases: check valid case, then check invalid combinations by using
one invalid value with remaining valid values.
Weak
• more complex equivalence classes of valid input values
• variables may have several ranges of valid values
• test cases "cover" valid combinations
Strong
• equivalence classes as in weak form
• cross product of equivalence classes of valid input values
• presumes variables are independent
We compare these for a function of three variables, F(x
, x
, x ) 1 2 3

4. Forms of Equivalence Class Testing
Normal: classes of valid values of inputs
Robust: classes of valid and invalid values of inputs
Weak: (single fault assumption) one from each class
Strong: (multiple fault assumption) one from each class in Cartesian Product
We compare these for a function of three variables, F(x1, x2, x3)

6. Weak Robust Equivalence Class Test Casesd x 2 1
Equivalence Classes:
Valid(x
) : a Š x
Š b; Invalid(x
) : x
Š a , x
 b 1 1 1 1 1
Valid(x
) : c Š x
Š d; Invalid(x
) : x
Š c , x
 d 2 2 2 2 2

7. Weak Robust Equivalence Class Testing
Variable
Valid input set x a1 e
V1X1, a2 e
V2X1 1 x b1 e
V1X2, b2 e
V2X2, b3 e
V3X2, b4 e
V4X2 2 x c1 e
V1X3, c2 e
V2X3, c3 e
V3X3 3
Test cases
F(a1, b1, c1)
F(a2, b2, c2)
F(a1, b3, c3)
F(a2, b4, c1)

8. Weak Normal Equivalence Class Test Casesx 2 g f e a b c d x 1
Equivalence Classes: x
: a Š x
Š b, b < x
Š c, c < x
Š d 1 1 1 1 x
: e Š x
Š f, f < x
Š g 2 2 2

9. Strong Normal Equivalence Class Testing
Variable
Valid input set x a1 e
V1X1, a2 e
V2X1 1 x b1 e
V1X2, b2 e
V2X2, b3 e
V3X2, b4 e
V4X2 2 x c1 e
V1X3, c2 e
V2X3, c3 e
V3X3 3
Test cases
F(a1, b1, c1), F(a1, b1, c2), F(a1, b1, c3)
F(a1, b2, c1), F(a1, b2, c2), F(a1, b2, c3)
F(a1, b3, c1), F(a1, b3, c2), F(a1, b3, c3)
F(a1, b4, c1), F(a1, b4, c2), F(a1, b4, c3)
F(a2, b1, c1), F(a2, b1, c2), F(a2, b1, c3)
F(a2, b2, c1), F(a2, b2, c2), F(a2, b2, c3)
F(a2, b3, c1), F(a2, b3, c2), F(a2, b3, c3)
F(a2, b4, c1), F(a2, b4, c2), F(a2, b4, c3

10. Strong Normal Equivalence Class Test Casesx 2 g f e a b c d x 1
Equivalence Classes: x
: a Š x
Š b, b < x
Š c, c < x
Š d 1 1 1 1 x
: e Š x
Š f, f < x
Š g 2 2 2