COTS Testing

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COTS Testing

Diff. With in-house components Interface (pre and post conditions) are not clearly specified. No Arch. and code. Black boxes to component user.

Why use COTS

Why COTS Testing

Failure of Ariane5. explosion resulted from insufficiently tested software reused from the Ariane 4 launcher.

COTS Evaluation and selection

Why rigorous evaluation of COTS? Large number of alternative products. Multiple stakeholders. Large number of Quality criteria. Compatibility with other products.

Why evaluation difficult Large number of evaluation criteria. Different opinions are usually encountered among different stakeholders. Evaluation criteria are not easily measurable at evaluation time. Gathering relevant info. is prohibitively expensive. COTS market is changing fast, evaluation must be performed several times during lifecycle. Evaluation deals with uncertainty info.

AHP Technique Originally designed for economic and political science domains. Requires a pair wise comparison of alternatives and pair wise weighting of selection criteria. Enables consistency analysis of comparisons and weights, making possible to assess quality of gathered info.

AHP Technique (contd.) Allows alternatives to be measured on a ratio scale,we can determine how much better an alternative compared to other. Practically usable if number of alternatives and criteria are sufficiently low, because comparisons are made by experts.

Selection in practiceFollows three stages Informal screening for a set of requirements using selection thresholds. More systematic evaluation using AHP process. Detailed Information gathering involves testing, prototyping and reading technical documents.

State of the art in COTS testing

How to provide information to user Component meta-data approach. Retro-components approach. Component test bench approach. Built-in test approach. Component+ approach. STECC strategy.

Component meta-data approachComponent

Binary code


Call graphs, Testing info. done by provider

Component metadata (contd.)Componentfunctionality Metadata req Metadata


Meta DB

Retro-components approachComponentfunctionality Metadata req and test data Metadata


Meta DB

Component test bench approach A set of test cases called test operation is associated with each interface of a component. A test operation defines the necessary steps for testing a specific method. The concrete test inputs and expected test output packaged in a test operation.

Built-in test approach.ComponentFunctionality

Test case generator


Built-in test approach(contd.)Normal mode. Maintenance mode.

Functionality Functionality Test case generator Tester

Built-in test approach(contd.)Base Component


Derived Component

Component+ approachTester

Built-in testing enabled componentTest case generator



Test executorFailure Recovery mech.s


Disadv. of BIT and component+ Static nature. Generally do not ensure that tests are conducted as required by the component user The component provider makes some assumptions concerning the requirements of the component user, which again might be wrong or inaccurate.

STECC strategyquery

functionalityMetadata Req.



Meta DB

Metadata Test generator

Levels of Testing Unit Testing. Integration Testing. System Testing

Types of testing Functionality Testing . Reliability Testing. Robustness Testing. Performance Testing. Load Testing. Stress Testing. Stability Testing. Security Testing.

Certifying COTSWhen considering a candidate component, developers need to ask three key questions: Does component C fill the developers needs? Is the quality of component C high enough? What impact will component C have on system S?

Certifying COTS(contd.)

CERTIFICATION TECHNIQUES Black-box component testing. System-level fault injection. Operational system testing. Software Wrapping. Interface propagation Analysis.

Black box Testing To understand the behavior of a component, various inputs are executed and outputs are analyzed. To catch all types of errors all possible combinations of input values should be executed. To make testing feasible, test cases are selected randomly from test case space.

Black box test reduction using Input-output Analysis Random Testing is not complete. To perform complete functional testing, number of test cases can be reduced by Input-output Analysis.

How to find I/O relationships By static analysis or execution analysis of program.

Fault Injection


Fault simulation toolErroneous or malicious input


Fault simulation tool

Exceptions, No response

Operational System Testing complements system-level fault injection. System is operated with random inputs (valid and invalid inputs) Provides more accurate assessment of COTS quality. To ensure that a component is a good match for the system.

Software WrappingInput wrapper Output wrapper




Instrumentation configuration file

Interface propagation Analysis

COTS Component 1

Fault Injector

COTS Component 2

Modify input, call correct method. Call correct method, modify output. Call perturbed function.

Fault Injection used for Robustness Testing. Error propagation Analysis. Reliability Testing. Security Testing.

Robustness Testing

COTS testing for OS failures

COTS component


Operating System

Ballista approach Based on fault injection technique. Test cases are generated using parameter types of an interface. Independent of internal functionality. Testing is not complete.

Test value Data Base

Test value Data Base(contd.) Integer data type: 0, 1, -1, MAXINT, -MAXINT, selected powers of two, powers of two minus one, and powers of two plus one. Float data type: 0, 1, -1, +/-DBL_MIN, +/DBL_MAX, pi, and e. Pointer data type: NULL, -1 (cast to a pointer), pointer to freed memory, and pointers to malloced buffers of various powers of two in size.

Test value Data Base(contd.) String data type (based on the pointer base type): includes NULL, -1 (cast to a pointer), pointer to an empty string, a string as large as a virtual memory page, a string 64K bytes in length. File descriptor (based on integer base type): includes 1;MAXINT; and various descriptors: to a file open for reading, to a file open for writing, to a file whose offset is set to end of file, to an empty file, and to a file deleted after the file descriptor was assigned.

Test case generation All combinations of values for the parameter types are generated. Number of test cases generated are product of number of parameters and test base for that type.

Error propagation analysis Interface Propagation Analysis is used by injecting faults at one component. This is done at component integration level. A known faulty input is injected using fault injector into the system. Components effected by this input are observed (how they handle the faulty input).

Performance Testing

Middleware Applications execution and Middleware cannot be divorced in any meaningful way. In order to predict the performance of application component, performance of its middleware should be analyzed.

Performance prediction MethodologyApplications performance prediction is three step process. Obtaining Technology performance. Analyzing Architecture specific behavioral characteristics. Analyzing Application specific behavioral characteristics.

Technology performance profile

Technology performance profile (contd.)

Technology performance profile (contd.)

Architecture behaviorIdentity Application

Effect of database access thru MiddlewareContainerSession bean Entity bean


The performance of the entity bean architecture is less than 50% of the performance of the session bean only Architecture.

Effect of Server Thread The performance increases from 2 threads to 32 threads, stabilizes around 32 to 64 threads, and gradually decreases as more threads are added due to contention.

The Effect of Client Request Load. Client response time increases with concurrent client request rate due to contention for server threads.

Effect of Database Contention Effect of database contention leads to performance that is between 20% and 49%.

Optimal Number of threads

Load Testing

Load Testing It is just Performance testing under various loads. Performance is measured as Connections per second (CPS), throughput in bytes per second, and round trip time (RTT) .

Load Test ApplicationLoad test App


Web server

System Under Test App server DB server

Testing strategyLoad tests will be conducted in three phases.1. Consumption of server resources as a function of the volume of incoming requests will be measured. 2. Response time for sequential requests will be measured. 3. Response time for concurrent client request load will be measured.

Security Testing

Security Risks with COTS Component design. Component procurement. Component integration. System maintenance.

Component Design Inadvertently flawed component design. Intentionally flawed component design. Excessive component functionality. Open or widely spread component design. Insufficient or incorrect documentation.

Component integrationMismatch betw