Designing For Testability

1
Designing For Testability
2
Designing For Testability

• Incorporate design features that facilitate
  testing
• Include features to
• support test automation at both the unit and
  system levels
• provide visibility into the programs internal
  state and activities
• (this allows more specific and accurate bug
  reports)

3
Verbose output mode
mail -v bret_at_pettichord.com Subject testability
example Sample text. . Cc bret_at_pettichord.com...
Connecting to mx.io.com. via relay...
220-deliverator.io.com ESMTP Sendmail
8.9.3/8.9.3 Fri, 12 Jan 2001 153436 -00 220
Welcome to Illuminati Online, Fnord! EHLO
eris.io.com 250-deliverator.io.com Hello
IDENTwazmo_at_eris.io.com 199.170.88.11, pleased
tu 250-8BITMIME 250-SIZE 5000000 250-DSN 250-ONEX
250-ETRN 250-XUSR 250 HELP MAIL From
SIZE67 250
... Sender ok RCPT To
250 ...
Recipient ok DATA 354 Enter mail, end with
. on a line by itself . 250 PAA07752
Message accepted for delivery bret_at_pettichord.com.
.. Sent (PAA07752 Message accepted for delivery)
Closing connection to mx.io.com. QUIT 221
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Example quoted from Design for Testability by
Bret Pettichord
4
Logging events to a file
class Log public const int DEBUG 1
const int INFO 2 const int WARNING
3 const int ERROR 4 const int FATAL
5 // send log output to the console
Log() // send log
output to a file Log(const string
file) // Send log output to a remote
server Log(const string serverIpAddress,
int serverPort) // Only log messages with
priority minPriority void
SetMinPriority(Priority minPriority) // Log
messages with the various priorities
Debug(const string message) Info(const
string message) Warning(const string
message) Error(const string message)
Fatal(const string message)
5
Asserts

• Asserts are little test cases distributed
  throughout the code
• Abortive asserts (crash if assert fails)
• Logging asserts (log message if assert fails)

6
The Mock Object design pattern

• Allows a class to be isolated from its
  dependencies during unit testing
• Supports fault injection
• Cause the software to fail at points where it
  normally wouldnt to test error handling code
• Example URL Spelling Checker

7
Provide automation interfaces

• When possible, test cases should be automated
  with test scripts
• Test Script a program that runs a batch of
  automated test cases and reports the results
• User interfaces often do not lend themselves to
  automation (especially GUIs)
• Programs can provide automation interfaces that
  allow test scripts to run commands and query
  application state without going through the user
  interface
• Cmd-line interface (e.g., test-tracker
  add-test-plan Word10)
• Execute batch command file (e.g., test-tracker
  run-batch cmds.txt)
• Web service API

8
Data generators loaders

• Creating large data sets by hand is not feasible
• Think about trying to manually enter large
  amounts of test plan and defect data in Test
  Tracker
• Data Generator
• A program that generates large amounts of test
  data
• Configuration parameters let the user shape the
  generated data
• Data Loader
• A program that loads generated test data into the
  application
• Example Test Tracker Data Generator Loader