Basic Definitions About Software Testing

Basic Definitions About Software Testing51Testing软件测试网/jp1E~J&y

 51Testing软件测试网&A'p};G"O

Much of testing literature is mired in confusing (and sometimes inconsistent) terminology,probably because testing technology has evolved over decades and via scores of writers. The terminology here (and throughout this book) is taken from standards developed by theInstituteofElectronicsand Electrical Engineers(IEEE) Computer Society. To get started, let us look at a useful progression of terms.51Testing软件测试网GzJ|N
sH r

Error——people make errors. A good synonym is mistake. When people make mistakes while coding, we call these mistakes bugs. Errors tend to propagate; a requirements error may be magnified during design and amplified still more during coding.

Fault——a fault is the result of an error. It is more precise to say that a fault is the representation of an error, where representation is the mode of expression, such as narrative text, dataflow diagrams, hierarchy charts, source code, and so on. Defect is a good synonym for fault, as is bug. Faults can be elusive. When a designer makes an error of omission, the resulting fault is that something is missing that should be present in the representation. This suggests a useful refinement; to borrow from the church, we might speak of faults of commission and faults of omission. A fault of commission occurs when we enter something into a representation that is incorrect. Faults of omission occur when we fail to enter correct information. Of these two types, faults of omission are more difficult to detect and resolve.51Testing软件测试网@7fRF){ v|to

Failure——a failure occurs when a fault executes. Two subtleties arise here: one is that failures only occur in an executable representation, which is usually taken to be source code, or more precisely, loaded object code; the second subtlety is that this definition relates failures only to faults of commission. How can we deal with failures that correspond to faults of omission? We can push this still further: What about faults that never happen to execute, or perhaps do not execute for a long time? The Michaelangelo virus is an example of such a fault. It does not execute until Michaelangelo’s birthday, March 6. Reviews prevent many failures by finding faults; in fact, well-done reviews can find faults of omission.

Incident——when a failure occurs, it may or may not be readily apparent to the user (or customer or tester). An incident is the symptom associated with a failure that alerts the user to the occurrence of a failure.

Test——testing is obviously concerned with errors, faults, failures, and incidents. A test is the act of exercising software with test cases. A test has two distinct goals: to find failures or to demonstrate correct execution.51Testing软件测试网&k4WV0? M PX5r+C

Test Case——test case has an identity and is associated with a program behavīor. A test case also has a set of inputs and a list of expected outouts.51Testing软件测试网?*HK4Rx Y8q