Bottom Up Approach:

The bottom up approach testing approach is carried out with the help of the test driver. The test driver calls a component to be tested.

The modules in the lower level of call hierarchy are tested independently. Then the next level modules are tested that call previously tested modules. This is done repeatedly until all the modules are included in the testing.

Bottom up testing stops when the top module in the call hierarchy is tested with all lower call hierarchy modules.

Top Down Approach:

The top down approach is carried out with the help of the test stub. Test stub are the dummy programs. The Stub is called from the software component to be tested.

Tests top layer of controlling subsystem first. Then combine modules that are called by the tested modules and test resulted collection of modules.

Do this until all the modules are combined and tested.

Use Case: A use case is a description of the process which is performed by the end user for a particular task. Use case contains a sequence of step which is performed by the end user to complete a specific task or a step by step process that describe how the application and end user interact with each other. Use case is written by the user point of view.

Use case Testing: the use case testing uses this use case to evaluate the application. So that, the tester can examines all the functionalities of the application. Use case testing cover whole application, tester performs this testing in step by step process to complete one task

Software testing is verifying if a software meets the customer's requirements; if it has high quality; if it is bug free and if it is fit for use. Testing is important because it ensures that the product delivered is defect free which in turn emphasizes higher quality and proves to be cost effective.

While a test plan is being created, risks involved in testing the product are to be taken into consideration along with possibility of their occurrence and the damage they may cause along with solutions; if any. Detailed study of this is called as Risk Analysis.

Some of the risks could be:

New Hardware 

New Technology 

New Automation Tool 

Sequence of code delivery 

Availability of application test resources 

Identify and describe the risk magnitude indicators: High, Medium and Low

High magnitude means the effect of the risk would be very high and non-tolerable. Company may face severe loss and its reputation is at risk. Must be tested.

Medium: tolerable but not desirable. Company may suffer financially but there is limited liability or loss of reputation. Should be tested.

Low: tolerable. Little or no external exposure. Little or no financial loss. Company’s reputation unaffected. Might be tested.

Three perspectives of Risk Assessment: Effect, Cause and Likelihood.

To assess risk by Effect, identify a condition, event or action and try to determine its impact.

To asses risk by Cause is opposite of by Effect. Begin by stating an undesirable event or condition and identify the set of events that could have permitted the condition to exist.

To asses risk by Likelihood is to determine the probability that a requirement will not be satisfied.