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there is no need for the test tool for use cases and test case as ..both of them are documents used for test planning & execution , they are used for both manual as well as automation ...
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Use Cases are another extrapolation layer on Requirements. They further define the "behaviour" of the software and the "user" (being a real person or another program) and the different scenarios of that usage/behaviour. This may (and should) include the 'positive' paths/behaviour and the negative paths/behaviour, and if it is a negative behaviour how it will resolve/handle the situation.
Now what I just wrote is not the end-all definition, but it is a simplified description of a Use Case based on RUP.
Test Cases on the other hand are the documents that define the process of verifying the Requirement/Use Case/whatever is referenced to describe the behaviour of the software/system. There are multiple types of tests and the cases that support them.