Export (0) Print
Expand All

Magic Numbers: Integers

Josh Poley

Microsoft Corporation

Introduction

In testing software, we often miss an entire class of bugs just because we don't happen to think about one category of inputs and how they might adversely affect the system. To help combat this in with my own tests, I've pulled together a listing of numbers which are good to use in testing for various independent reasons.

At the very least, here are some free numbers which you can stick into your tests; pick the ones that make sense and add them to your regression tests. But better yet, you can use some of these numbers as a brainstorm to help spurn ideas about other classes of values to test in your application. To give you a brief sample, here are some of the categories covered here:

  • Common character values
  • Common boundaries
  • Times and dates
  • Colors
  • Security - We cover values that often lead to overflow attacks, as well as characters used in cross site scripting and SQL injection attacks.
  • Primes - Prime numbers are good because they can't be divided up nicely.

You may also want to treat the below numbers as boundaries themselves. Depending on your application it might make sense to not only supply the value listed here, but also add or subtract 1 from the number.

8 bit Integers (0 - 255)

Value

Hex

Description

0

0x00

Zero. False. Terminating NULL character.

1

0x01

One.

2

0x02

Two.

3

0x03

Prime.

4

0x04

Four. Size of a 32 bit integer or pointer. 2^2.

5

0x05

Five fingers. Prime.

7

0x07

2^3 - 1. Largest single digit octal value. Seven days in a week. Prime.

8

0x08

2^3.

10

0x0A

Humans usually think in decimal, so arrays, lists, etc. are often a multiple of ten.

15

0x0F

2^4 - 1. Largest single digit hexadecimal value.

16

0x10

2^4.

24

0x18

Hours in a day.

32

0x20

2^5.

34

0x22

Numerical value for the double quote ASCII character which is often used in cross site scripting attacks.

37

0x25

Numerical value for the ASCII character '%' which is an escape sequence in URLs and the C run time library.

38

0x26

Numerical value for the ASCII character '&' which is often used in cross site scripting attacks.

39

0x27

Numerical value for the single quote ASCII character which is often used in cross site scripting attacks.

42

0x2A

Aside from a book/movie reference, developers often use this as an arbitrary value.

48

0x30

Numerical value for the ASCII character '0' (zero).

52

0x34

Number of weeks in a year.

59

0x3B

Numerical value for the ASCII character ';' which is often used in SQL injection and cross site scripting attacks.

60

0x3C

Number of seconds in a minute. Number of minutes in an hour. Numerical value for the ASCII character '<' which is often used in cross site scripting attacks.

62

0x3E

Numerical value for the ASCII character '>' which is often used in cross site scripting attacks.

64

0x40

26.

65

0x41

Numerical value for the ASCII character 'A'. 2^6 + 1.

85

0x55

Repeating "01" bit pattern.

90

0x5A

90 degrees.

97

0x61

Numerical value for the ASCII character 'a'.

99

0x63

Two nines. Largest 2 digit value.

100

0x64

100.

127

0x7F

2^7 - 1. The maximum signed 8 bit value. Largest 7 bit prime. Last character in the standard ASCII character map.

128

0x80

2^7.

170

0xAA

Repeating "10" bit pattern.

204

0xCC

x86 assembly instruction, if executed, halts the process ("int 3").

251

0xFB

Largest 8 bit prime.

255

0xFF

The maximum unsigned 8 bit value (2^8 - 1). Maximum filename length on several common file systems. Blue in a 24 bit RGB format.

Raw List

0, 1, 2, 3, 4, 5, 7, 8, 10, 15, 16, 24, 32, 34, 37, 38, 39, 42, 48, 52, 59, 60, 62, 64, 65, 85, 90, 97, 99, 100, 127, 128, 170, 204, 251, 255

16 bit Integers (256 - 65,535)

Value

Hex

Description

256

0x0100

2^8.

257

0x0101

2^8 + 1.

260

0x0104

MAX_PATH.

360

0x0168

Number of degrees in a circle.

365

0x016D

Number of days in a year.

512

0x0200

2^9.

1000

0x03E8

Number of milliseconds in a second.

1024

0x0400

Kilobyte. 2^10.

1601

0x0641

Year when time started according to the Windows FILETIME format.

1970

0x07B2

Year when time started according to the CRT time_t format.

1999

0x07CF

Just before Y2K.

2004

0x07D4

A leap year.

2100

0x0834

Year divisible by four but is not actually a leap year.

3600

0x0E10

Number of seconds in an hour.

4095

0x0FFF

2^12 - 1.

4096

0x1000

4k. 2^12. Size of a page of memory on Windows. Common file system cluster size.

4097

0x1001

2^12 + 1.

9999

0x270F

Four nines. Largest value under 10000.

16383

0x3FFF

2^14 - 1.

16384

0x4000

16k. 2^14. Common file system cluster size.

16385

0x4001

2^14 + 1.

32749

0x7FED

Largest 15 bit prime.

32767

0x7FFF

2^15 - 1. The maximum signed 16 bit value.

32768

0x8000

32k. 2^15. On a 16 bit platform, this value times 2 (the size of an integer) will overflow to 0.

32769

0x8001

2^15 + 1.

65280

0xFF00

Green in a 24 bit RGB format.

65521

0xFFE1

Largest 16 bit prime.

65535

0xFFFF

The maximum unsigned 16 bit value (2^16 - 1).

Raw List

256, 257, 260, 360, 365, 512, 1000, 1024, 1601, 1970, 1999, 2004, 2100, 3600, 4095, 4096, 4097, 9999, 16383, 16384, 16385, 32749, 32767, 32768, 32769, 65280, 65521, 65535

32 bit Integers (65,536 - 4,294,967,295)

Value

Hex

Description

65536

0x00010000

2^16.

65537

0x00010001

2^16 + 1.

131072

0x00020000

128k.

1048576

0x00100000

Megabyte.

5550100

0x0054B014

Start of the fictional phone number range.

5550199

0x0054B077

End of the fictional phone number range.

16711680

0x00FF0000

Red in a 32 bit RGB format.

16777215

0x00FFFFFF

White in a 24 bit RGB format.

999999999

0x3B9AC9FF

Nine nines. Largest 32 bit value with all 9s.

1073741824

0x40000000

Gigabyte. On a 32 bit platform, this value times 4 (the size of an integer) will overflow to 0.

1431655765

0x55555555

Repeating 01 bit pattern.

2130706433

0x7F000001

Equivalent to 127.0.0.1 in a packed IP format (loop back address).

2147483647

0x7FFFFFFF

The maximum signed 32 bit value. Largest 31 bit prime.

2851995649

0xA9FE0000

Equivalent to 169.254.0.1 in a packed IP format (auto IP address).

2863311530

0xAAAAAAAA

Repeating 10 bit pattern.

3221225472

0xC0000000

Three gigabytes, which is the size of addressable memory when Windows applications use the /LARGEADDRESSAWARE linker switch.

4294967291

0xFFFFFFFB

Largest 32 bit prime.

4294967295

0xFFFFFFFF

The maximum unsigned 32 bit value (2^32 - 1).

Raw List

65536, 65537, 131072, 1048576, 5550100, 5550199, 16711680, 16777215, 999999999, 1073741824, 1431655765, 2130706433, 2147483647, 2851995649, 2863311530, 3221225472, 4294967291, 4294967295

64 bit Integers (4,294,967,296 - 18,446,744,073,709,551,615)

Value

Hex

Description

4294967296

0x0000000100000000

2^32.

4294967297

0x0000000100000001

2^32 + 1.

36000000000

0x0000000861C46800

One hour in the Windows FILETIME format.

1099511627776

0x0000010000000000

Terabyte.

4222222222222

0x000003D7100E438E

Visa test credit card number.

30569309025904

0x00001BCD78CE3670

Diners Club test credit card number.

38520000023237

0x00002308A2EB0AC5

Diners Club test credit card number.

371449635398431

0x000151D4DB91E31F

American Express test credit card number.

378282246310005

0x0001580BB2EA8875

American Express test credit card number.

378734493671000

0x00015874FEF59E58

Corporate American Express test credit card number.

1125899906842624

0x0004000000000000

Petabyte.

3530111333300000

0x000C8A9E1809F720

JCB test credit card number.

3566002020360505

0x000CAB428BB12139

JCB test credit card number.

4012888888881881

0x000E41B380BEB2D9

Visa test credit card number.

4111111111111111

0x000E9B08A568F1C7

Visa test credit card number.

5105105105105100

0x00122310E854B0CC

MasterCard test credit card number.

5555555555554444

0x0013BCBF936B348C

MasterCard test credit card number.

5610591081018250

0x0013EECD885D338A

Australian BankCard test credit card number.

6011000990139424

0x0155AF93AC304200

Discover test credit card number.

6011111111111117

0x0155B12DE7BB1CD0

Discover test credit card number.

1152921504606846976

0x1000000000000000

Exabyte.

2305843009213693952

0x2000000000000000

On a 64 bit platform, this value times 8 (the size of an integer) will overflow to 0.

9223372036854775783

0x7FFFFFFFFFFFFFE7

Largest 63 bit prime.

9223372036854775807

0x7FFFFFFFFFFFFFFF

The maximum signed 64 bit value.

9999999999999999999

0x8AC7230489E7FFFF

Nineteen nines. Largest 64 bit value with all 9s.

18446744073709551557

0xFFFFFFFFFFFFFFC5

Largest 64 bit prime.

18446744073709551615

0xFFFFFFFFFFFFFFFF

The maximum unsigned 64 bit value.

Raw List

4294967296, 4294967297, 36000000000, 1099511627776, 4222222222222, 30569309025904, 38520000023237, 371449635398431, 378282246310005, 378734493671000, 1125899906842624, 3530111333300000, 3566002020360505, 4012888888881881, 4111111111111111, 5105105105105100, 5555555555554444, 5610591081018250, 6011000990139424, 6011111111111117, 1152921504606846976, 2305843009213693952, 9223372036854775783, 9223372036854775807, 9999999999999999999, 18446744073709551557, 18446744073709551615

Negative Integers

The constants here are the specific to signed integer values, and should be used when applications utilize negative inputs. To compliment your test cases, be sure to pull numbers from the above tables (after changing their sign) as many of them maintain appropriateness in the negative domain.

Value

Description

-1

Negative one.

-128

Minimum signed 8 bit value.

-32768

Minimum signed 16 bit value.

-2147483248

Minimum signed 32 bit value.

-9223372036854775808

Minimum signed 64 bit value.

Raw List

-1, -128, -32768, -2147483248, -9223372036854775808

Closing Thoughts

Since everything is stored as a number, this really only brushes the tip of what could (or should) be considered "important". For your own tests, you will want to think about the domain and come up with the best values to ensure good coverage in your code base. The numbers here are just stock values, and you will definitely want to "build your own" numbers. For example, look for hard coded values in the code you are testing, and use these. You will also want to look for interfaces which take a count of objects; fabricate and pass in a count which when multiplied by the size of the object will cause an integer overflow.

About the Author

Josh Poley has been a tester at Microsoft since 1998. He initially worked on the very first version of the Passport authentication service (currently called Windows Live ID). Then, in the spring of 2000, Josh moved over and joined a small handful of people who were starting to work on a project code-named Xbox. His initial responsibilities covered various pieces of the low level operating system (file systems, peripheral communication, etc.). Shortly after the Xbox game console launched in 2001, Josh took over as lead of the Kernel Test Team and remained in charge of validating the core operating system throughout the development and launch of the Xbox 360. Then, in the spring of 2007, Josh joined the Zune group as a Test Architect, where he helped solve various problems across the four main test teams in the organization. After a year in Zune, Josh went back to Xbox to help solve some more hard problems there.

Show:
© 2014 Microsoft