The approaches that we use for bug isolation are :-
1- Bottom-up Approach
2- Top-down Approach
3- Bisection Approach
4- Refinement Approach

Bottom Up Approach:- The bottom-up approach is used when testers have an intuition about the items of the defect/issue, such as the test data. It implicate creating a very little test environment and notice if it reproduce the defect. If the defect is not reproduced, then add a few portions of the original environment to the minimal environment to reproduce it.

Top-down Approach:- The Top-down approach is used when the intuitive approaches followed by testers are not enough to decrease the environment significantly. It is a systematic approach for removing irrelevant details from the original environment to provide a minimal capable environment to reproduce the reported defect/issue.

Bisection Approach:- The Bisection Approach also make referral to as a binary search is depend on the search algorithm that is used for searching sorted lists. But with few innovative thinking we can easily use this algorithm for defect/issue isolation.

Refinement Approach:- When the defect/issue/bug has been isolated , there is still an opportunity to determine additional information about it through the use of the refinement approach. The main focus of this approach is on characterizing the severity of the defect and starting the debugging mechanism.