SDSU CS 683 Emerging Technologies: Embracing Change
Spring Semester, 2001
Some Testing
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© 2001, All Rights Reserved, SDSU & Roger Whitney
San Diego State University -- This page last updated 29-Mar-01

Contents of Doc 17, Some Testing

References

Refactoring: Improving the Design of Existing Code, Fowler, Addison-Wesley, 1999

Testing for Programmers: A tutorial for OOPSLA 2000, Brian Marick, http://www.testing.com/writings/half-day-programmer.pdf

Used here with permission from Brian Marick

A Short Catalog of Test Ideas, Brian Marick, http://www.testing.com/writings/short-catalog.pdf

Used here with permission from Brian Marick 


Doc 17, Some Testing Slide # 2

Some Testing

Fowler on Testing [1]

"Make sure all tests are fully automatic and that they check their own results"

"It is better to write and run incomplete tests than not to run complete tests"

"Don't let the fear that testing can't catch all bugs stop you from writing the tests that will catch most bugs"

"Trying to write too many tests usually leads to not writing enough"

"Run your tests frequently"

"When you get a bug report, start by writing a unit test that exposes the bug"

Think of the boundary conditions and concentrate your tests there 


Doc 17, Some Testing Slide # 3
Programming Errors

Programmers tend to make the same errors many times

Keep a list or catalog of your errors 

Doc 17, Some Testing Slide # 4

A Short Catalog of Test Ideas


Tests develop catalogs of commonly found errors in programs

Since errors are often repeated, this helps testers find common errors

As programmers such a catalog:
If we know these are common errors, we can keep them in mind while coding



The following catalog is from Brian Marick

http://www.testing.com/writings/short-catalog.pdf

The catalog is used here with permission 

Doc 17, Some Testing Slide # 5

Any Object


Test nil(null) references and pointers to objects

In Java/Smalltalk

Does the code handle correctly variables & parameters that are null(nil)

Java

   String firstName = null
Smalltalk

   | firstName  |
   firstName := nil.


Doc 17, Some Testing Slide # 6

Strings


Test the empty string

Does the code to the correct thing when string variables/parameters are the empty string

In Java/Smalltalk an empty string is not the same as a null(nil) reference to a string

Java

   String firstName = "";
   String secondName = new String();
Smalltalk

   | firstName secondName |
   firstName := ''.
   secondName := String new


Doc 17, Some Testing Slide # 7

Numbers


Test the code using:

Often numbers are used in a context with a valid range
The smallest number refers to the smallest valid number in the range

Example 

int planetIndex;   //Represents the I'th planet from the Sun

Numbers to test
0
 Below the smallest
1
 Smallest
9
 Largest (Pluto is still considered a planet)
10
 Above the largest 

Doc 17, Some Testing Slide # 8

Collections


Test the code using:
Not the largest possible collection allowed by the language/hardware
The largest possible collection the system will encounter
If this is not possible use a collection with more than one element 

Doc 17, Some Testing Slide # 9

Linked Structures (trees, graphs, etc.)


Test the code using:

The test must make the code reach the lowest depth
If the structure in the context has a maximally deep use that level 

Doc 17, Some Testing Slide # 10

Equality Testing of Objects


Objects have two meanings of equality

Two object references point to the same memory location

The fields of the two objects have the same value

Java

Tests if two object references are pointer identical
Tests if two objects are equal
If this method is not implemented in a class it defaults to ==


Smalltalk

Tests if two object references are pointer identical
Tests if two objects are equal
If this method is not implemented in a class it defaults to == 

Doc 17, Some Testing Slide # 11

Test the code with objects equal but not identical

Lack of pointer identity should extend as far down as is meaningful to the code



Test the code with objects different at the lowest level 

Doc 17, Some Testing Slide # 12
"Trying to write too many tests usually leads to not writing enough ... You get many benefits from testing even if you do a little testing ..."

Fowler
Doc 17, Some Testing Slide # 13
[1] Fowler Chapter 4, pp. 89-102

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2001 SDSU & Roger Whitney, 5500 Campanile Drive, San Diego, CA 92182-7700 USA.
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