The test case design techniques are broadly grouped
into two categories: Black box techniques, White box techniques and
other techniques that do not fall under either category.
Black Box (Functional)
- Specification derived tests
- Equivalence partitioning
- Boundary Value Analysis
- State-Transition Testing
White Box (Structural)
- Branch Testing
- Condition Testing
- Data Definition - Use Testing
- Internal boundary value testing
Other- Error guessing
Specification Derived Tests
As the name suggests, test cases are designed by walking through the
relevant specifications. It is a positive test case design technique.
Equivalence Partitioning
Equivalence partitioning is the process of taking all of the possible
test values and placing them into classes (partitions or groups). Test
cases should be designed to test one value from each class. Thereby, it
uses fewest test cases to cover the maximum input requirements.
For example, if a program accepts integer values only
from 1 to 10. The possible test cases for such a program would be the
range of all integers. In such a program, all integers upto to 0 and
above 10 will cause an error. So, it is reasonable to assume that if 11
will fail, all values above it will fail and vice versa.
If an input condition is a range of values, let one
valid equivalence class be the range (0 or 10 in this example). Let the
values below and above the range be two respective invalid equivalence
values (i.e. -1 and 11). Therefore, the above three partition values
can be used as test cases for the above example.
Boundary Value Analysis
This is a selection technique where the test data are chosen to lie
along the boundaries of the input domain or the output range. This
technique is often called as stress testing and incorporates a degree
of negative testing in the test design by anticipating that errors will
occur at or around the partition boundaries.
For example, a field is required to accept amounts of
money between $0 and $10. As a tester, you need to check if it means
upto and including $10 and $9.99 and if $10 is acceptable. So, the
boundary values are $0, $0.01, $9.99 and $10.
Now, the following tests can be executed. A negative
value should be rejected, 0 should be accepted (this is on the
boundary), $0.01 and $9.99 should be accepted, null and $10 should be
rejected. In this way, it uses the same concept of partitions as
equivalence partitioning.
State Transition Testing
As the name suggests, test cases are designed to test the transition
between the states by creating the events that cause the transition.
Branch Testing
In branch testing, test cases are designed to exercise control flow
branches or decision points in a unit. This is usually aimed at
achieving a target level of Decision Coverage. Branch Coverage, need to
test both branches of IF and ELSE. All branches and compound conditions
(e.g. loops and array handling) within the branch should be exercised
at least once.
Condition Testing
The object of condition testing is to design test cases to show that
the individual components of logical conditions and combinations of the
individual components are correct. Test cases are designed to test the
individual elements of logical expressions, both within branch
conditions and within other expressions in a unit.
Data Definition – Use Testing
Data definition-use testing designs test cases to test pairs of data
definitions and uses. Data definition is anywhere that the value of a
data item is set. Data use is anywhere that a data item is read or
used. The objective is to create test cases that will drive execution
through paths between specific definitions and uses.
Internal Boundary Value Testing
In many cases, partitions and their boundaries can be identified from a
functional specification for a unit, as described under equivalence
partitioning and boundary value analysis above. However, a unit may
also have internal boundary values that can only be identified from a
structural specification.
Error Guessing
It is a test case design technique where the testers use their
experience to guess the possible errors that might occur and design
test cases accordingly to uncover them.
Using any or a combination of the above described test case design techniques; you can develop effective test cases.
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