An Example

The module is to compute the tax for an employee. Tax is 10% of salary if salary is less than $10,000, or 15% of salary if salary is greater than or equal to $10,000.

Black Box Tests

Test Id     Input (Salary)     Output (tax)  Equivalence Class
 101          7,000            700       Low tax class
 102         11,000           1650       High tax class
 103        -100          error     Boundary value
 104          0             0       Boundary value

White Box Tests

if salary < 10000 then  tax = salary x 0.1
                  else  tax = salary x 0.15
The actual tests will achieve branch coverage 
Test Id     Input (Salary)     Output (tax)  Branch Covered
 101          5,000            500       first branch
 102         12,000           1800       second branch