In general testing is comparing actuals versus expected when having as objective to control that the system respects the requirements defined by the client. Testing should satisfy the need for information on the differences between the object and the defined requirements. But more than that, we need to know the causes behind the problems and identify and help to resolve those causes.
So based on the analysis, the causes will be determined, the problem will be consistently solved, and future risks can be foreseen. In summary, the quality of the system will be improved. A principle of quality, also sustained by Agile, is that it is better to foresee than to solve. A high severity defect solved in early stage, during build for example, will cost less than a minor production issue.
While in manual testing the tester executes manually the test going through the test cases, in automation testing he makes use of separate special software (test tool own built code) to control the execution of tests comparing the actual outcomes with predicted outcomes. Tests so carried out, can be run repeatedly, at any time of day with several advantages:

• Test scripts and results of testing activities are centrally accessible, as they can be shared.
• Accuracy improvement as the same steps will always be performed without human mistake
• Flexibility in its applicability: Sometimes automation testing involving stubs for example, and will make test possible while manual testing could not.
• Repeatability and time saving increasing the test coverage.

With those advantages, although automated test requires more effort for setting-up, the ROI (Return On Investment) will be guaranteed.
Are you facing an automation testing challenge and expect the above mentioned advantages in your project, you can refer to Losseni Keita. There is no tool which can fluently and universally be applied at any project. Each project has its specificities and therefore the automation tester also programmer needs sometimes to be creative and produce some adapted solutions. Losseni can produce tailored solutions using JAVA or XSLT, but he also has experience of several test tools and not least such as HP UFT, SELENIUM, BDD Serenity, JMETER, BLAZEMETER, CONCORDION