root:
             product   file:plan.py
             product   step:./plan.py

file:plan.py
               state = CONFIRMED
             creator   root:
                sink   step:./plan.py

step:./plan.py
               state = SUCCEEDED
                need = PLAN
           using_env = INP_VAR_TEST_STEPUP_WORKDIR [dynamic]
                     = STEPUP_PATH_FILTER [dynamic]
             creator   root:
              source   file:plan.py
             product   file:sub/input.txt
             product   step:cat input.txt > output.txt  # wd=sub

file:sub/input.txt
               state = CONFIRMED
             creator   step:./plan.py
                sink   step:cat input.txt > output.txt  # wd=sub

step:cat input.txt > output.txt  # wd=sub
               state = SUCCEEDED
                need = DEFAULT
             creator   step:./plan.py
              source   file:sub/input.txt
             product   file:sub/output.txt
                sink   file:sub/output.txt

file:sub/output.txt
               state = BUILT
             creator   step:cat input.txt > output.txt  # wd=sub
              source   step:cat input.txt > output.txt  # wd=sub
