How to use external packages from the test directory

[walkre]

Hi, Nim community!

Now I wanna use an external package in the test directory. For example like the 
below code:
    
    
    import unittest
    import epackage # an external package
    
    suite "a suite":
      test "a test":
        check:
          someProcedure() # a procedure in epackage
    
    
    Run

However, the way like the above doesn't work well.

So how should I import external packages like nimble file? 
    
    
    requires epackage
    
    
    Run