Testing: Chapter 13

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Testing Chapter 13

• "You make it, Ill break it"

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Purpose

• Does the product as a whole perform up to
  specifications? (validation?)
• Does it perform under normal, upper, and lower
  limits wrt the environment?
• Does it meet or exceed all claims (verification)?

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Testing defined

• establishing confidence that a device does what
  it is supposed to do
• the process of operating a device with the intent
  of finding errors
• detecting specification errors and deviations
  from the specification

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Testing continued

• verifying that a system satisfies its specified
  requirements or identifying differences between
  expected and actual results
• the process of operating a device or component
  under specified conditions, observing or
  recording the results, and making an evaluation
  of some aspect of the system or component.

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Testing

• Is a positive act of destruction.
• Is needed for good product development
• Is necessary for consumer satisfaction

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Stressors (depend on requirements)
Temperature Humidity
Altitude Shock
Vibration EMI
Cell phone, pagers Brownouts
ESD Spillage
Shipping Power Surges
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Figure 13-1 Requirements checklist
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Customer Misuse

• Coffee spillage
• Drop in toilet
• Use as a seat
• Cross-connecting
• Reverse polarity
• Dirty hands
• Unplugging via jerk on cable

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Testing requires that you define failure!

• Intended application?
• Anticipated environment?
• Lifetime?
• Value vs. time
• Sunken ships make good coral reefs in time

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Types of testing

• Event testing cycling, time to failure
• Environmental operating storage
• Altitude
• Threshold (door, elevator, bricks )
• Vibration
• ISTA shipping test
• EMI (standards!, see next slide )

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EN 1000 series standards

• Radiated electric field immunity
• Fast transients
• Surge, line, magnetic
• Dips, variations, V, F variation
• On/off, ESU
• Walkie-talkie, cell phone
• ESU, etc.

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Failure Definition

• For each test and for each device, a failure
  must be defined. This definition depends on the
  intended application and the anticipated
  environment. What is considered a failure for
  one component or device may not be a failure for
  another. The test protocol should be as detailed
  as possible in defining the failure.

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We want to test some power supplies to prove a
MTBF goal of 50,000 hours of operation. How many
units do we test and for how long, assuming one
failure and 90 confidence level?
(sample size)(test time) MTBF goal
(7.779)/2 (sample size)(test time) 50,000
(7.779)/2 194,475
unit-hours
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Determining Sample Size and Test Length
MTBF goal (sample size)(test time) (2)/?2
a2r2
Confidence level 1 - a, where a is the risk
factor and r the number of failures
Example---------------------------
Using the 90 confidence level, a 0.10 no
failures (r0)
(Sample size)(test time) (MTBF goal)( ?2 a2
)/2
(sample size)(test time) MTBF goal (4.61)/2
to prove a MTBF goal of 50,000 hours of operation
(sample size)(test time) 50,000 (4.61)/2

115,250 unit-hours
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Types of Testing Verification

• Procedures that attempt to determine that the
  product of each phase of the development process
  is an implementation of a previous phase, i.e.,
  it satisfies it. Each verification activity is a
  phase of the testing life cycle

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Types of Testing Validation

• Validation is the process of evaluating a system
  or component during or at the end of the
  development process to determine whether it
  satisfies specified requirements

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Types of Testing Black Box

• Black box testing is a data driven testing
  scheme. The tester views the device or program
  as a black box, i.e., the tester is not concerned
  about the internal behavior and structure. The
  tester is only interested in finding
  circumstances in which the device or program does
  not behave according to its specification

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Types of Testing White Box

• White box testing is concerned with the degree
  to which test cases exercise or cover the
  structure of the device or program. The ultimate
  while box test is an exhaustive path test.

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Types of testing Software

• Module
• Integration
• System
• Acceptance

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Types of testingFuctional

• This type of testing verifies that given all the
  expected inputs then all of the expected outputs
  are produced. This type of testing is termed
  success oriented testing because the tests are
  expected to produce successful results.

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Types of testing - continued

• Robustness Testing
• Stress Testing
• Safety testing
• Regression Testing

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Types of testing, continued

• Life test/reliability
• Customer misuse
• Fluid spillage
• Weight test
• Keyed connections
• Time related
• Failure related (MTBF)

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Questions?