Assertion (software development): Difference between revisions

Revision as of 12:19, 18 August 2020

Revision as of 12:19, 18 August 2020

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In [[Java (programming language)|Java]], <code>%</code> is the ''[[remainder]]'' operator (''[[Modulo operation|modulo]]''), and in Java, if its first operand is negative, the result can also be negative (unlike the modulo used in mathematics). Here, the programmer has assumed that <code>total</code> is non-negative, so that the remainder of a division with 2 will always be 0 or 1. The assertion makes this assumption explicit: if <code>countNumberOfUsers</code> does return a negative value, the program may have a bug.

a major advantage of this technique is that when an error does occur it is detected immediately and directly, rather than later through often obscure effects. Since an assertion failure usually reports the code ___location, one can often pin-point the error without further debugging.

Assertions are also sometimes placed at points the execution is not supposed to reach. For example, assertions could be placed at the <code>default</code> clause of the <code>switch</code> statement in languages such as [[C (programming language)|C]], [[C++]], and [[Java (programming language)|Java]]. Any case which the programmer does not handle intentionally will raise an error and the program will abort rather than silently continuing in an erroneous state. In [[D (programming language)|D]] such an assertion is added automatically when a <code>switch</code> statement doesn't contain a <code>default</code> clause.