Many times Tester need common sense to test a application!!!
Why it's like this because most of the times it is not possible to test the entire application within the specified time. In such situations it’s better to find out the risk factors in the projects and concentrate on them.
Here are some points to be considered when you are in such a situation:
1) Find out Important functionality is your project?
2) Find out High-risk module of the project?
3) Which module is most visible to the user?
4) Which functionality has the largest security impact?
5) Which module has the largest financial impact on users and admins?
6) Which aspects of the application are most important to the customer?
7) Which code snippet is most complex, and thus most subject to errors?
8) Which parts of the application were developed in rush or panic mode?
9) What do the developers think are the high-risk aspects of the app?
10) What kinds of problems would cause the poor publicity?
11) What kinds of problems would cause the most customer issues?
12) What kinds of tests could easily cover multiple scenarios?
1) Find out Important functionality is your project?
2) Find out High-risk module of the project?
3) Which module is most visible to the user?
4) Which functionality has the largest security impact?
5) Which module has the largest financial impact on users and admins?
6) Which aspects of the application are most important to the customer?
7) Which code snippet is most complex, and thus most subject to errors?
8) Which parts of the application were developed in rush or panic mode?
9) What do the developers think are the high-risk aspects of the app?
10) What kinds of problems would cause the poor publicity?
11) What kinds of problems would cause the most customer issues?
12) What kinds of tests could easily cover multiple scenarios?
Considering these points you can greatly reduce the risk of project releasing under less time constraint.
Value of QA just fyi...