Saturday, January 26, 2008
Saturday, January 19, 2008
Software Testing
Software Testing:
It is a destructive process,yes a creative destruction.
Testing adds value to the program by increasing your level of confidence in it.
Testing adds value to the program by raising its quality or reliability.
Testing - When is a program correct?
There are levels of correctness. We must determine the appropriate level of correctness for each system because it costs more and more to reach higher levels.
No syntactic errors
Compiles with no error messages
Runs with no error messages
There exists data which gives correct output
Gives correct output for required input
Correct for typical test data
Correct for difficult test data
Proven correct using mathematical logic
Obeys specifications for all valid data
Obeys specifications for likely erroneous input
Obeys specifications for all possible input
Testing - How do you do it?
Reference: Myers, The Art of Software Testing
You might also consult
Pfleeger, Software Engineering, Chapters 7 - 8 Sommerville, Software Engineering, Chapters 20 - 23
Testing is the process of executing a program with the intent of finding errors .
A good test case is one which has a high probability of detecting an as yet undiscovered error.
A successful test case is one which detects an as yet undiscovered error.
An unsuccessful test case is one for which the program produces the correct result.
Test cases must be written for the invalid and the unexpected, as well as for the valid and expected.
"Testing is the process of demonstrating that errors are not present" (or that "the system works correctly") is an impossible task
Testing to uncover errors is a feasible task.
Thoroughly inspect the results of each test. Compare carefully with the expected results.
An error is present if the program does not do what it is supposed to do.
An error is also present if the program does what it is not supposed to do.
A programmer should avoid attempting to test his or her own program.
A programming organization should avoid attempting to test its own programs.
Testing - How do you do it
Black box testing (data driven or input/output driven)
Not concerned about the internal behavior or structure Test cases are derived solely from the specifications. Exhaustive input testing --- Desirable, but impossible Create equivalence classes of test cases Programs with memory.
White box testing (logic driven)
Examine the internal structure, Execute every statement, Execute every path. Too many paths --- May still not match its specifications
--- Solving the wrong problem?
--- Missing paths
--- Data sensitivity
Testing - Test case design
What subset of all possible test cases has the highest probability of detecting the most errors?
Logic coverage testing
Decision (branch) coverage
--- Each decision is true once and false once
Condition coverage
--- Each condition in a decision takes all possible values Decision/condition coverage
Equivalence partitioning
Good test case reduces by more than one the number of other test cases which must be developed .Good test case covers a large set of other possible cases Classes of valid inputs Classes of invalid inputs
Boundary value analysis
Situations on, above, or below edges of input, output, condition classes have high probability of success
Cause-effect graphing
Myers gives a formal methodology Explore combinations of conditions Good way to uncover ambiguities and incompleteness in specifications
Error guessing
Intuition and experience Maintain a list of possible errors or error-prone situations
The Strategy - Some of all
Testing - How do you do it?
Myers also discusses
Program inspections, walkthroughs, and reviews Module testing High-order (integration) testing, Debugging strategies, Test tools
Testing - What are the milestones?
Reference: Pfleeger, Software Engineering, Chapter 8.
The test results demonstrate that the test criteria for each module, and for the system, have been met. For each test performed, the test results typically include:
Means of control - initiate and control by manual or automatic means
Test data - includes input data, input commands, output data, and messages produced by the system
Test script - step-by-step description of how to perform the test, including how to end it Results - evidence that the test was performed according to its data and script specifications
For each error or deficiency uncovered, a discrepancy report typically includes:
State of the system before the error occurred.
Evidence of the error
Action which appears to have led to the error's occurrence
Description of how the system should work
Reference to relevant requirements
Impact of the error on system performance
Source of the error
Changes made to remove the error
A detailed record of errors discovered and corrected during development often saves hours of maintenance time.
Testing - What tools are available to help you?
See Myers, The Art of Software Testing, Chapter 8
Module drivers
Static flow analysis
Test coverage
Mathematical proofs of correctness
Program correctness proving programs
Symbolic execution
Test data generators
Environment simulators
Virtual machines
Software error studies
Software error data collection
Predictive models
Complexity measures
Program library systems
Interactive debugging
It is a destructive process,yes a creative destruction.
Testing adds value to the program by increasing your level of confidence in it.
Testing adds value to the program by raising its quality or reliability.
Testing - When is a program correct?
There are levels of correctness. We must determine the appropriate level of correctness for each system because it costs more and more to reach higher levels.
No syntactic errors
Compiles with no error messages
Runs with no error messages
There exists data which gives correct output
Gives correct output for required input
Correct for typical test data
Correct for difficult test data
Proven correct using mathematical logic
Obeys specifications for all valid data
Obeys specifications for likely erroneous input
Obeys specifications for all possible input
Testing - How do you do it?
Reference: Myers, The Art of Software Testing
You might also consult
Pfleeger, Software Engineering, Chapters 7 - 8 Sommerville, Software Engineering, Chapters 20 - 23
Testing is the process of executing a program with the intent of finding errors .
A good test case is one which has a high probability of detecting an as yet undiscovered error.
A successful test case is one which detects an as yet undiscovered error.
An unsuccessful test case is one for which the program produces the correct result.
Test cases must be written for the invalid and the unexpected, as well as for the valid and expected.
"Testing is the process of demonstrating that errors are not present" (or that "the system works correctly") is an impossible task
Testing to uncover errors is a feasible task.
Thoroughly inspect the results of each test. Compare carefully with the expected results.
An error is present if the program does not do what it is supposed to do.
An error is also present if the program does what it is not supposed to do.
A programmer should avoid attempting to test his or her own program.
A programming organization should avoid attempting to test its own programs.
Testing - How do you do it
Black box testing (data driven or input/output driven)
Not concerned about the internal behavior or structure Test cases are derived solely from the specifications. Exhaustive input testing --- Desirable, but impossible Create equivalence classes of test cases Programs with memory.
White box testing (logic driven)
Examine the internal structure, Execute every statement, Execute every path. Too many paths --- May still not match its specifications
--- Solving the wrong problem?
--- Missing paths
--- Data sensitivity
Testing - Test case design
What subset of all possible test cases has the highest probability of detecting the most errors?
Logic coverage testing
Decision (branch) coverage
--- Each decision is true once and false once
Condition coverage
--- Each condition in a decision takes all possible values Decision/condition coverage
Equivalence partitioning
Good test case reduces by more than one the number of other test cases which must be developed .Good test case covers a large set of other possible cases Classes of valid inputs Classes of invalid inputs
Boundary value analysis
Situations on, above, or below edges of input, output, condition classes have high probability of success
Cause-effect graphing
Myers gives a formal methodology Explore combinations of conditions Good way to uncover ambiguities and incompleteness in specifications
Error guessing
Intuition and experience Maintain a list of possible errors or error-prone situations
The Strategy - Some of all
Testing - How do you do it?
Myers also discusses
Program inspections, walkthroughs, and reviews Module testing High-order (integration) testing, Debugging strategies, Test tools
Testing - What are the milestones?
Reference: Pfleeger, Software Engineering, Chapter 8.
The test results demonstrate that the test criteria for each module, and for the system, have been met. For each test performed, the test results typically include:
Means of control - initiate and control by manual or automatic means
Test data - includes input data, input commands, output data, and messages produced by the system
Test script - step-by-step description of how to perform the test, including how to end it Results - evidence that the test was performed according to its data and script specifications
For each error or deficiency uncovered, a discrepancy report typically includes:
State of the system before the error occurred.
Evidence of the error
Action which appears to have led to the error's occurrence
Description of how the system should work
Reference to relevant requirements
Impact of the error on system performance
Source of the error
Changes made to remove the error
A detailed record of errors discovered and corrected during development often saves hours of maintenance time.
Testing - What tools are available to help you?
See Myers, The Art of Software Testing, Chapter 8
Module drivers
Static flow analysis
Test coverage
Mathematical proofs of correctness
Program correctness proving programs
Symbolic execution
Test data generators
Environment simulators
Virtual machines
Software error studies
Software error data collection
Predictive models
Complexity measures
Program library systems
Interactive debugging
Amod Purandare
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Sunday, September 16, 2007
Bajaj - Pulsar 200
This, hold your breath, biker boyz, is a Pulsar-200!Merely weeks after springing a revamped Pulsar 180 on us without any buzz or promotions, Bajaj has pulled another fast one yet again.Despite being parked in the shadows of its bigger sibling, the P-200 is the first brute that catches your eye at the Auto Expo in Mumbai.The squat, 18 bhp, oil-cooled beast ensures that you don't even throw as much as a cursory glance towards the much-hyped DTS-FI.The naked chain makes gives it the perfect, mean, made-for-the-streets look.To be launched in Bajaj's pro-biking showrooms in January 2007, (that's what the Bajaj guy in the stall at the expo promised) the P-200 has most of the goodies from the bigger Pulsar. Tubeless tyres, the LCD speedo/analog tacho dash, split seats, two-piece grab rails, you name it and the P-200 has it.Everything except the fuel injection, that is.The bike, according to the Bajaj guys, is said to be "slightly costlier than the Pulsar 180."Which means, come January you must be able to lay your hands on the beast at around a miserly Rs 70,000.These pictures should keep you rubbing your palms and smacking your lips till then.Just in case images of the P-220 are still in your memory, the DTS-FI will be out by April 2007, we are promised.
Transformer Designing
Chapter 1
IntroductionThe number of industries is growing at a very fast rate. Also the requirement of electronic equipments is also good. Hence components those are required to design electronic equipment are in good number.One of the components having large requirement is Power Transformer. So as to increase the number of power transformers per unit time I have designed this software. This software will be helpful not only to the designers but also to the user. This idea can be used and can be improved for all type of equipments, components, and devices staring from simple transformer to advanced computers, mobile phones. I have design a program in ’C’ language for designing a power transformer. The program is interactive and prompts the user for entering the various inputs via inputs via keyboard.It uses graphics mode for display. Please ensure that the transformer designer using this software is having controller card in the PC supports graphics mode. This is application-oriented software.This is very simple to use. Any literate person can use this software.I have also observed how to prepare a transformer in company [Siddhanath enterprises].So after getting values from the program as an output one can design the values for designing the transformer. By this way one can design the transformer. Here I have designed the power transformer for Cold Rolled Grain Oriented [CRGO] type of material.Now the following chart explain what are the parameters to be entered and what are the outputs that we get as an output as shown in table-1. TABLE-1Parameters to be enteredParameters that software providesinput voltageprimary wattageoutput voltagesecondary wattagefrequencylamination typesecondary currentdimensionsthickness of laminationcore areathickness of butter paperturns per voltlayers of butter paperturns of primaryallowed errorturns of secondarytype of transformer-step up / step downprimary currentturns per inchdiameter of primary coildiameter of secondary coilstandard wire guagewinding widthlayers of primary windinglayers of secondary windingtotal laminations requiredWhy we need the transformer
Chapter 2
Theoretical BackgroundTransformersTransformer is the most basic application of the principle of electronic induction. In elementary terms it consists of two coils [usually copper] physically placed so that magnetic field in one links the other through air or ferro magnetic core.When one coil [primary] is connected to a generator source, and secondary is connected to load, changing current in primary produces a changing magnetic field common to both coils and results in transfer of electrical energy from the input circuit to output circuit.Principle -Mutual inductionTypes of Transformers –1.Power Transformer2.Matching Transformer3.Audio Transformer4.Intermediate Frequency Transformer5.Radio Frequency Transformer6.Auto Transformer7.Variable Transformer8.Linear Variable Differential TransformerPower transformerPower transformers are used to change voltage and current levels of electrical energy. Being a two winding system they provide isolation between the primary and secondary. Most common use of power transformers is in rectifier circuits.There are two basic core type structures viz. 1.core type 2.shell typeCore type: In the core type structure a single core with a single window provides a single magnetic path.Shell type: In the shell type structure a single coil surrounds two cores in such a way that the magnetic field becomes equal to both the cores, which divide magnetic flux between them.The Power transformers used expressly for the power supplies is a mains transformer. This uses laminated cores-usually the E-I shaped. The most important specification of such a transformer is the volt-amp rating [V-A rating] of each secondary. This is the product of maximum secondary current and the secondary voltage. The primary V-A rating depends on transformer efficiency.Transformer regulation is another important spec in its use in power supply circuits. One has to take into account the desired specification values while designing a transformer.Though the transformer related equations i.e. Equations relating primary and secondary voltage and current are so simple, the actual design of a real transformer is not. One would expect it to be so by looking at the equivalent circuit of a transformer several factors are involved and several design equations containing different terms are involved.Following points must be known while designing the transformer.1.Voltage rating2. Efficiency3.Required regulation4.Operating temperature range5.Permitted sizeFrequency response of a transformerAt low frequencies there is little effect of leakage inductance and shunt capacitance. Lost due to dc resistance, skin effect and over losses. At low frequencies these losses are less. Main cause of attenuation at low frequencies is the value of reactance. The output increases as frequencies.
Chapter 3
Equivalent circuit of a transformerEquivalent circuit of a transformerTransformer construction-An electronic transformer can be considered to be made up of several physical systems.Magnetic circuit –It consists of the core [of any magnetic material] and the magnetic path.Electric circuit-This consists of successive turns of wire, usually single strands of insulated copper or aluminuam wire. Higher operating frequency application calls for use of Litz wire. Litz wire is made up of multiple strands of individually insulated wires.Transformers cores –The component most responsible for shape, size, weight when the magnetic core is used. We have already seen typically used core materials. Strip core laminations are used for power, audio, large pulse transformer. These are insulated from to prevent eddy current losses. Laminated cores are fabricated in various shapes. Apart from these ferrite cores and powered iron cores are also used typically for high frequency applications.LAMINATIONS-Insulation system-This consists of insulation on the magnet wire; sheet insulation which may be used between layers of the winding and between winding themselves; various plastic impregnants used to provide mechanical support, heat transfer, and/or environmental protection.Various gaseous or liquid dielectric and the miscellaneous tapes and adhesives. The selection of material for this purpose depends on many factors such as their compatibility with each other, allowable temperature, expected life of transformer etc.In addition voltage considerations, thermal considerations are also involved.
IntroductionThe number of industries is growing at a very fast rate. Also the requirement of electronic equipments is also good. Hence components those are required to design electronic equipment are in good number.One of the components having large requirement is Power Transformer. So as to increase the number of power transformers per unit time I have designed this software. This software will be helpful not only to the designers but also to the user. This idea can be used and can be improved for all type of equipments, components, and devices staring from simple transformer to advanced computers, mobile phones. I have design a program in ’C’ language for designing a power transformer. The program is interactive and prompts the user for entering the various inputs via inputs via keyboard.It uses graphics mode for display. Please ensure that the transformer designer using this software is having controller card in the PC supports graphics mode. This is application-oriented software.This is very simple to use. Any literate person can use this software.I have also observed how to prepare a transformer in company [Siddhanath enterprises].So after getting values from the program as an output one can design the values for designing the transformer. By this way one can design the transformer. Here I have designed the power transformer for Cold Rolled Grain Oriented [CRGO] type of material.Now the following chart explain what are the parameters to be entered and what are the outputs that we get as an output as shown in table-1. TABLE-1Parameters to be enteredParameters that software providesinput voltageprimary wattageoutput voltagesecondary wattagefrequencylamination typesecondary currentdimensionsthickness of laminationcore areathickness of butter paperturns per voltlayers of butter paperturns of primaryallowed errorturns of secondarytype of transformer-step up / step downprimary currentturns per inchdiameter of primary coildiameter of secondary coilstandard wire guagewinding widthlayers of primary windinglayers of secondary windingtotal laminations requiredWhy we need the transformer
Chapter 2
Theoretical BackgroundTransformersTransformer is the most basic application of the principle of electronic induction. In elementary terms it consists of two coils [usually copper] physically placed so that magnetic field in one links the other through air or ferro magnetic core.When one coil [primary] is connected to a generator source, and secondary is connected to load, changing current in primary produces a changing magnetic field common to both coils and results in transfer of electrical energy from the input circuit to output circuit.Principle -Mutual inductionTypes of Transformers –1.Power Transformer2.Matching Transformer3.Audio Transformer4.Intermediate Frequency Transformer5.Radio Frequency Transformer6.Auto Transformer7.Variable Transformer8.Linear Variable Differential TransformerPower transformerPower transformers are used to change voltage and current levels of electrical energy. Being a two winding system they provide isolation between the primary and secondary. Most common use of power transformers is in rectifier circuits.There are two basic core type structures viz. 1.core type 2.shell typeCore type: In the core type structure a single core with a single window provides a single magnetic path.Shell type: In the shell type structure a single coil surrounds two cores in such a way that the magnetic field becomes equal to both the cores, which divide magnetic flux between them.The Power transformers used expressly for the power supplies is a mains transformer. This uses laminated cores-usually the E-I shaped. The most important specification of such a transformer is the volt-amp rating [V-A rating] of each secondary. This is the product of maximum secondary current and the secondary voltage. The primary V-A rating depends on transformer efficiency.Transformer regulation is another important spec in its use in power supply circuits. One has to take into account the desired specification values while designing a transformer.Though the transformer related equations i.e. Equations relating primary and secondary voltage and current are so simple, the actual design of a real transformer is not. One would expect it to be so by looking at the equivalent circuit of a transformer several factors are involved and several design equations containing different terms are involved.Following points must be known while designing the transformer.1.Voltage rating2. Efficiency3.Required regulation4.Operating temperature range5.Permitted sizeFrequency response of a transformerAt low frequencies there is little effect of leakage inductance and shunt capacitance. Lost due to dc resistance, skin effect and over losses. At low frequencies these losses are less. Main cause of attenuation at low frequencies is the value of reactance. The output increases as frequencies.
Chapter 3
Equivalent circuit of a transformerEquivalent circuit of a transformerTransformer construction-An electronic transformer can be considered to be made up of several physical systems.Magnetic circuit –It consists of the core [of any magnetic material] and the magnetic path.Electric circuit-This consists of successive turns of wire, usually single strands of insulated copper or aluminuam wire. Higher operating frequency application calls for use of Litz wire. Litz wire is made up of multiple strands of individually insulated wires.Transformers cores –The component most responsible for shape, size, weight when the magnetic core is used. We have already seen typically used core materials. Strip core laminations are used for power, audio, large pulse transformer. These are insulated from to prevent eddy current losses. Laminated cores are fabricated in various shapes. Apart from these ferrite cores and powered iron cores are also used typically for high frequency applications.LAMINATIONS-Insulation system-This consists of insulation on the magnet wire; sheet insulation which may be used between layers of the winding and between winding themselves; various plastic impregnants used to provide mechanical support, heat transfer, and/or environmental protection.Various gaseous or liquid dielectric and the miscellaneous tapes and adhesives. The selection of material for this purpose depends on many factors such as their compatibility with each other, allowable temperature, expected life of transformer etc.In addition voltage considerations, thermal considerations are also involved.
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