Once the system has been created, it needs to be thoroughly tested.

A test plan is usually written whilst the system is being developed. The test plan will contain details of every single thing that needs to be tested.
For example:
  • Does the system open and close properly?
  • Can data be entered?
  • Can data be saved?
  • Can reports be printed?
  • When you do something wrong, does an error message appear?
  • Is invalid data rejected? E.g. if you are not allowed to enter an amount above £1,000 on the system then a value of 1,001 should not be accepted (i.e. does the validation work?)
Test plans are very detailed, and contain many tests. Each test is specified very precisely.

A typical test would contain:
  • Details of what is being tested
  • The test data to use
  • What is expected to happen when the test is performed


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Selecting Test Data

When choosing what data to use to test a system, you need to think about why we are testing the system: to see if it works, and to check it doesn't break.

To do this, we use three types of test data...
Normal Data Values
This is data that would normally be entered into the system.

The system should accept it, process it, and we can then check the results that are output to make sure they are correct.
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E.g. In a system that was designed to accept and process test marks (percentages), then normal test values would include:
  • 10
  • 25
  • 63
  • 89
Extreme Data Values
Extreme value are still normal data.

However, the values are chosen to be at the absolute limits of the normal range.

Extreme values are used in testing to make sure that all normal values will be accepted and processed correctly.
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E.g. In a system that was designed to accept and process test marks (percentages), then extreme test values would be:
  • 0 (lowest possible value)
  • 100 (highest possible value)
In systems that deal with text, the extreme values are defined by how long the text can be. The limits would be:
  • "" (nothing entered)
  • "ABCDEF..." (max. length)
Abnormal Data Values
This is data that should not normally be accepted by the system - the values are invalid.

The system should reject any abnormal values.

Abnormal values are used in testing to make sure that invalid data does not break the system.
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E.g. In a system that was designed to accept and process test marks (percentages), then abnormal test values would include:
  • -1
  • 101
  • 200
  • -55

When is the System Tested?

Testing is normally done in two stages...

The first phase of testing is done by the designers and engineers who created the system, usually before the system is delivered to the customer.

The test data that is used in this first phase is similar to data that would be used by the actual customer.

The second phase of testing is done after the system has been delivered and installed with the customer.

The data used in the second phase is usually 'live' data - data that is actually part of the customer's business / organisation.
These two phases of testing are often referred to as Alpha Testing (testing by the designers/engineers) and Beta Testing (testing by real users, with real data)

What Happens if the System Fails Some Tests?

The whole point of testing is to try and find areas that don't work as they should, or areas that can be improved.

If any failures are found, the systems analyst goes back and does some further research, analysis and design to fix these areas.

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