(OO) Integration Testing
Informally - a (design) point of view
What: Integration testing is a phase of software testing in which
individual software modules are combined and tested as a group.
It follows unit testing and precedes system testing.
Why: The purpose of integration testing is to verify functional,
performance and reliability requirements placed on major design
artefacts.
How: integration testing is a logical extension of unit testing. In its
simplest form, two units that have already been tested are combined
into a component and the interface between them is tested. But
choosing the integration order is non-trivial!
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.1
(OO) Integration vs RegressionTesting – another (incremental
development) point of view
Integration tests are performed when new code is added to an existing code
base; for example, when a new function is added to a set of existing functions.
Integration tests measure whether the new code works -- integrates -- with the
existing code; these tests look for data input and output, correct handling of
variables, etc.
Regression testing is the counterpart of integration testing: when new code is
added to existing code, regression testing verifies that the existing code
continues to work correctly, whereas integration testing verifies that the new
code works as expected.
Regression testing can describes the process of testing new code to verify that
this new code hasn't broken any old code.
Question: is this incremental view a good way of thinking about
integration testing or is the design view better?
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.2
Integration Testing: What about OO?
•The components to be tested are object classes that are instantiated as
objects
•Larger grain than individual functions so approaches to white-box testing
have to be extended
•No obvious ‘top’ to the system for top-down integration and testing
•Levels of integration are less distinct in object-oriented systems
•Cluster testing is concerned with integrating and testing clusters of
cooperating objects
•Identify clusters using knowledge of the operation of objects and the
system features that are implemented by these clusters
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.3
Integration Testing: What Clusters?
•
Use-case or scenario testing
Testing is based on a user interactions with the system
Has the advantage that it tests system features as
experienced by users
•
Thread testing
Tests the systems response to events as processing threads
through the system
•
Object interaction testing
Tests sequences of object interactions that stop when an
object operation does not call on services from another
object
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.4
(OO) Integration Testing
Tests complete systems or subsystems composed of
integrated components
Integration testing should be black-box testing with tests
derived from the specification
Main difficulty is localising errors
Incremental integration testing reduces this problem
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.5
Integration of components
Component testing
•Testing of individual program components
•Usually the responsibility of the component developer
(except sometimes for critical systems)
•Tests are derived from the developer’s experience
Integration testing
•Testing of groups of components integrated to create a
system or sub-system
•The responsibility of an independent testing team
•Tests are based on a system specification
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.6
Integration of components
Component
testing
Integration
testing
Software developer
Independent testing team
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.7
Integration of components: test process is the
same
Test
cases
Design test
cases
2006-2007
Test
data
Prepare test
data
Test
results
Run program
with test data
INT-Evry (Masters IT– Soft Eng)
Test
reports
Compare results
to test cases
IntegrationTesting.8
Integration Testing Strategy
• The entire system is viewed as a collection of subsystems
(sets of classes) determined during the system and object
design.
• The order in which the subsystems are selected for testing
and integration determines the testing strategy
– Big bang integration (Nonincremental)
– Bottom up integration
– Top down integration
– Sandwich testing
– Variations of the above
• For the selection use the system decomposition from the
System Design
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.9
Example Design Structure: Three Layer Call Hierarchy
A
C
B
E
2006-2007
Layer I
F
INT-Evry (Masters IT– Soft Eng)
D
Layer II
G
Layer III
IntegrationTesting.10
Integration Testing: Big-Bang Approach
Unit Test
A
Unit Test
B
Unit Test
C
Not recommended
in all but the
simplest systems!
System Test
Unit Test
D
Unit Test
E
Unit Test
F
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.11
Bottom-up Testing Strategy
• The subsystem in the lowest layer of the call hierarchy are tested
individually
• Then the next subsystems are tested that call the previously tested
subsystems
• This is done repeatedly until all subsystems are included in the testing
• Special program needed to do the testing, Test Driver:
– A routine that calls a subsystem and passes a test case to it
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.12
Bottom-up Integration
A
E
Require
Driver: B
D
C
B
Unit Test E
Layer I
G
F
Layer II
Layer III
Test B, E, F
Unit Test F
Unit Test C Requires
Driver: A
Test
A, B, C, D,
E, F, G
Test D,G
Unit Test G Requires
Driver: G
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.13
Advantages and Disadvantages of bottom-up integration testing
• Bad for functionally decomposed systems:
– Tests the most important subsystem (UI) last
• Useful for integrating the following systems
– Object-oriented systems
– real-time systems
– systems with strict performance requirements
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.14
Top-down Testing Strategy
• Test the top layer or the controlling subsystem first
• Then combine all the subsystems that are called by the tested
subsystems and test the resulting collection of subsystems
• Do this until all subsystems are incorporated into the test
• Special program is needed to do the testing, Test stub :
– A program or a method that simulates the activity of a
missing subsystem by answering to the calling sequence of
the calling subsystem and returning back fake data.
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.15
Top-down Integration Testing
A
Test A
Test A, B, C, D
D
C
B
E
Layer I
G
F
Layer II
Layer III
Test
A, B, C, D,
E, F, G
Layer I
Layer I + II
Requires
stubs:
All Layers
BCD
2006-2007
EFG
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.16
Advantages and Disadvantages of top-down integration testing
• Test cases can be defined in terms of the functionality of the system
(functional requirements)
• Writing stubs can be difficult: Stubs must allow all possible conditions
to be tested.
• Possibly a very large number of stubs may be required, especially if
the lowest level of the system contains many methods.
• One solution to avoid too many stubs: Modified top-down testing
strategy
– Test each layer of the system decomposition individually before
merging the layers
– Disadvantage of modified top-down testing: Both, stubs and
drivers are needed
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.17
Sandwich Testing Strategy
• Combines top-down strategy with bottom-up strategy
• The system is view as having three layers
– A target layer ‘somewhere in the middle’
– A layer above the target
– A layer below the target
– Testing converges at the target layer
• How do you select the target layer if there are more than 3
layers?
– Heuristic: Try to minimize the number of stubs and
drivers
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.18
A
Sandwich Testing Strategy
C
B
E
Test E
Bottom
Layer
Tests
Layer I
F
D
G
Layer II
Layer III
Test B, E, F
Test F
Test D,G
Test
A, B, C, D,
E, F, G
Test G
Test A,B,C, D
Top
Layer
Tests
2006-2007
Test A
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IntegrationTesting.19
Advantages and Disadvantages of Sandwich Testing
• Top and Bottom Layer Tests can be done in parallel
• Does not test the individual subsystems thoroughly before
integration
• Solution: modified sandwich testing strategy:
– Test in parallel:
• Middle layer with drivers and stubs
• Top layer with stubs
• Bottom layer with drivers
– Test in parallel:
• Top layer accessing middle layer (top layer replaces drivers)
• Bottom accessed by middle layer (bottom layer replaces stubs)
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.20
Modified Sandwich Testing Strategy
Double
Test I
A
Test B
Triple
Test I
Triple
Test I
Test B, E, F
E
D
C
B
Test E
Layer I
G
F
Layer III
Double
Test II
Test F
Double
Test II
Layer II
Test D
Test D,G
Test
A, B, C, D,
E, F, G
Test G
Test A,C
Test A
Test C
2006-2007
Double
Test I
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IntegrationTesting.21
Steps in Integration-Testing
1. Based on the integration
strategy, select a component to
be tested. Unit test all the
classes in the component.
. 2. Put selected component together;
do any preliminary fix-up
necessary to make the
integration test operational
(drivers, stubs)
3. Do functional testing: Define
test cases that exercise all uses
cases with the selected
component
2006-2007
4. Do structural testing: Define test
cases that exercise the selected
component
5. Execute performance tests
6. Keep records of the test cases and
testing activities.
7. Repeat steps 1 to 7 until the full
system is tested.
The primary goal of integration
testing is to identify errors in the
(current) component
configuration.
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.22
Choosing an Integration Strategy?
•
•
Factors to consider
– Amount of test harness (stubs
&drivers)
– Location of critical parts in the
system
– Availability of hardware
– Availability of components
– Scheduling concerns
Bottom up approach
– good for object oriented design
methodologies
– Test driver interfaces must match
component interfaces
– ...
2006-2007
– ...Top-level components are
usually important and cannot
be neglected up to the end of
testing
– Detection of design errors
postponed until end of testing
• Top down approach
– Test cases can be defined in
terms of functions examined
– Need to maintain correctness
of test stubs
– Writing stubs can be difficult
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.23
Remember the Testing Life Cycle
Establish the test objectives
Design the test cases
Write the test cases
Test the test cases
Execute the tests
Evaluate the test results
Change the system
Do regression testing
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.24
How to
Construct
a Good
Test Team?
Professional
Tester
Programmer
too familiar
with code
Analyst
User
Test
Team
System
Designer
Configuration
Management
Specialist
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.25
In a complex system, you will probably need a test bench to coordinate testing activities
Test data
generator
Specification
Source
code
Test
manager
Test data
Oracle
Dynamic
analyser
Program
being tested
Test
results
Test
predictions
Execution
report
Simulator
File
comparator
Report
generator
2006-2007
INT-Evry (Masters IT– Soft Eng)
Test results
report
IntegrationTesting.26
(OO) Integration Testing
Lets learn about integration testing by looking at a practical example:
Check out the Source Code at the web site
We will use the IntPairArray from the regression testing
exercise:
IntPair.java,
Compare.java,
IntPairArray.java,
in our new system: Integration.java
It is your task to compare and contrast 2 different integration
testing approaches (e.g. big bang vs bottom-up) for this System.
2006-2007
INT-Evry (Masters IT– Soft Eng)
IntegrationTesting.27