Testing: Extreme Data

I am to test some forms using extreme data. I don't understand what it means by extreme data, could someone help me out pelase??

Thanks!

I believe this is more a figure of speech than the "extreme" term you sometimes find in the programming or testing worlds and would say this relates to exceptional out-of-the-ordinary values.

As a basis, you might want to consider and indeed extend by all means, some practise values I use myself:

1. Hold shift and run through any non alphanumeric character keys on the keyboard i.e. !"#¤% can be produced from the number keys 1-5. Repeat this without holding shift to capture more keys and on some keyboards, the right alt button allows for more of these symbols to be captured. Input this long string.
2. Enter the string "0123456789", then highlight and copy this. Paste this into the same field another 9 times. This will produce a string of 100 numbers, or charcaters. Highlight and copy this entire text, then paste it in another 2 times leaving you with a string of text 300 characters long. This will help test, for example, any saves to a database field with a defined length - i.e. of 128 or 255 characters and the behaviour of your app when the string passed is larger.
3. Goto Start > Run and enter CharMap.exe to bring up the character map application. Select multiple foreign characters such as ÄäÅåÖö and Chinese or Japanese ones too and input these.
4. Research (from say, Wikipedia) the term "SQLi" or "SQL injection" and input a string of text attempting to return a list of usernames from any backend database you may be using.

I think it means testing boundary value conditions.

Edge conditions would be my definition.

People tend to test with reasonable values, especially people who know what they are doing. This kind of test will work for many things, but it will fail in the case of typos, errors, and idiots, all of which are distressingly common. Therefore, you need to test not just for reasonable values, but for unreasonable values, too. Chimpanzees are good for this kind of testing, as long as the hardware can take it.

Among the things to test for, numeric data should definitely be tested for these three values: -1, 0, ten billion or higher. The reason for these three are that negative numbers often get overlooked, zero is often a problem for divisions, and numbers higher than an integer can hold are often overlooked.

I simply ask my wife: Can you break my program. And she does. This usually takes several rounds of testing. Even knowledgable users have an occasional misstyped character. One other area to look for is writing files to disk and catching quotes and commas used in comma delimited files. A stray comma or quote can really mess up the data.