• Software testability is the degree to which a software artifact (i.e. a software system, software module, requirements- or design document) supports testing in a given test context. If the testability of the software artifact is high, then finding faults in the system (if it has any) by means of testing is easier.

The effort and effectiveness of software tests depends on numerous factors including:

• Properties of the software requirements
• Properties of the software itself (such as size, complexity and testability)
• Properties of the test methods used
• Properties of the development- and testing processes
• Qualification and motivation of the persons involved in the test process

Requirements need to fulfil the following criteria in order to be testable: - consistent

• complete

• unambiguous

• quantitative (a requirement like "fast response time" can not be verification/verified)

• verification/verifiable in practice (a test is feasible not only in theory but also in practice with limited resources)

Requirements need to fulfil the following criteria in order to be testable: - consistent

• complete

• unambiguous

• quantitative (a requirement like "fast response time" can not be verification/verified)

• verification/verifiable in practice (a test is feasible not only in theory but also in practice with limited resources)

Requirement testability :

A testable requirement is a requirement that has been broken down to a level where it is precise, unambiguous, and not divisible into lower level requirements. These criteria are only met if it is possible to write a test case that would validate whether the requirement has or has not been implemented correctly. This is the source of the term "testable requirement". For most requirements, a testable requirement could be described in terms of:

• The state of the system and the data elements that are inputs (e.g., customer number, product number)

• The condition or action associated with the requirement (e.g., the user enters data, the order is validated, the check amount is deducted)

• The expected or specified result described in terms of data elements (e.g., customer number must be 8 digit numeric, product quantity must be greater than zero).