The test levels to be performed in testing and the description of testing activities within those test levels is known as test strategy.
There are many types of test strategy and selection of appropriate test strategy is the major factor behind testing success.
Test strategy also comes in test deliverables, the test strategy which is followed for testing should be informed to the project stakeholders.
Following are the major types of test strategies that are followed in software testing:
Risk based test strategy
Requirements based test strategy
Consultative or Directed