1. Unit Test Pattern

2. Unit Testing The focus is the module a programmer has written
Most often UT is done by the programmer himself
UT will require test cases for the module
UT also requires drivers to be written to actually execute the module with test cases
Besides the driver and test cases, tester needs to know the correct outcome as well

3. Unit Test Pattern Good unit tests are difficult to write
"the code is good when it passes the unit tests“
Unit test should be written first, before the code that is to be tested
Challenges
Unit testing must be formalized
Design also must be formally performed

4. Unit Test Patterns Pass/fail patterns Collection management patterns
Data driven patterns
Performance patterns
Simulation patterns
Multithreading patterns
Stress test patterns
Presentation layer patterns
Process patterns

5. Pass/Fail Patterns First line of defense to guarantee good code
Simple-Test Pattern
Code-Path Pattern
Parameter-Range Pattern

6. Simple Test-Pattern Code Pass/Fail results tell us that
Expected Result
Condition A
Condition B
Expected Failure
Pass/Fail results tell us that
the code under test will work/trap an error given the same input (condition) as in the unit test
No real confidence that the code will work correctly or trap errors with other set of conditions

7. Code-Path Pattern Emphasizes on conditions that
Code paths
Code path A
Path result
Code path B
Path result
Emphasizes on conditions that
test the code paths with in the unit rather than conditions that test for pass/fail
Results are compared to expected output of given code path
Caveat: How do you test code-paths if tests are written first?

8. Parameter-Range Pattern
Success set
Code paths
Code path A
Path result
Code path B
Path result
Failure set
Code-Path pattern with more than a single parameter test

9. Data Driven Test Patterns
Patterns which enable testing units with a broad range of input output pairs
Simple-Test-Data Pattern
Data-Transformation-Test Pattern

10. Simple-Test-Data Pattern
Data Set
Input
Output
Computation Code
Unit Test
Verify Result
Reduces complexity of Parameter-Range unit by separating test data from the test.
Test data is generated and modified independent of the test
Results are supplied with the data set.
Candidates for this pattern: Checksum Calculations, algorithims, etc…

11. Data-Transformation-Test Pattern
Input test data
Validation
Transformation code
Unit test
Measurement
Works with data in which a qualitative measure of the result must be performed.
Typically applied to transformation algorithms such as lossy compression

12. Data Transaction Patterns
Patterns embracing issues of data persistence and communication
Simple-Data-I/O Pattern
Constraint Data Pattern
The Rollback Pattern

13. Simple-Data-I/O Pattern
Service
Write test
Read Test
Verifies the read/write functions of the service

14. Constraint Data Pattern
Nullable
Unique
Default value
Foreign key
Cascading update
Cascading delete
Service
Write test
Constraints
Adds robustness to Simple-Data-I/O pattern by
Testing more aspects of the service
Any rules that the service may incorporate
Unit test verifies the service implementation itself
For example, DB schema, web service, etc…

15. Rollback Pattern Verifies rollback correctness
Service
Write test
Write test
Verifies rollback correctness
Most transactional unit tests should incorporate ability to rollback dataset to known state
In order to undo test side effects

16. Collection Management Patterns
Used to verify that the code is using the correct collection
Collection-Order Pattern
Enumeration Pattern
Collection-Constraint Pattern
Collection-Indexing Pattern

17. Collection-Order Pattern
Unordered
Code Containing Collection
Unordered data
Sequenced
Ordered
Verifies expected results when given an unordered list
The test validates that the result is as expected
Unordered, ordered or same sequence as input
Provides implementer with information on how the container manages the collections

18. Code Containing Collection
Enumeration Pattern
Edge test
Code Containing Collection
Expected datum
Enumerator (FWD, REV)
Collection
Verifies issues of enumeration or collection traversal
Important test when connections are non-linear.
E.g. collection tree nodes
Edge conditions (past first or last item) are also important to test

19. Collection-Constraint Pattern
Write test
Collection container
Nullable
Unique
Constraints
Verifies that the container handles constraint violations
Null values and duplicate keys
Typically applies to key-value pair collections

20. Collection-Indexing Pattern
Write test
Collection container
Index Key
Out of bound index
Update/ Delete Index
Index test
Verifies and documents indexing methods that the collection must support – by index and/or by key
Verifies that update and delete transactions that utilize indexing are working properly and are protected against missing indexes

21. Performance Patterns Used to test non functional requirements as
performance and resource usage
Performance-Test Pattern

22. Performance-Test Pattern
Pass
Metric at Start
Metric at End
Code
Pass criteria
Fail
Types of performance that can be measured:
Memory usage (physical, cache, virtual)
Resource (handle) utilization
Disk utilization (physical, cache)
Algorithm Performance (insertion, retrieval)

23. Pattern Summary
Unit Test patterns cover broad aspects of development; not just functional
May promote unit testing to become a more formal engineering discipline
Helps identify the kind of unit tests to write, and its usefulness.
Allows developer to choose how detailed the unit tests need to be