How to perform the trap test according to the trapman file.
report of the trap test (cf. trapman)

Step 0.
Move the trap directory to the mf directory, and cd to the trap directory.
This protects the original files like trap.log from being overwritten.
Copy trap.mf to the trap directory.
$ cp ../trap.mf .

Step 1. Prepare a version of inimf. You might want to use the nifty
script mktrap:
$ cd ..
$ mktrap
...
$ itgl mf.web mf.ch
...
$ mv inimf ~/bin
$ cd -

Step 2. run inimf
$ inimf
This is METAFONT-FPC, 3rd ed. (INIMF)
**
Please type the name of your input file or Control-D.
**\input trap
...
mv trap.log trapin.log
See diff_trapin.log for the differences of ../trapin.log and trapin.log

Step 3. run inimf again
$ inimf
This is METAFONT-FPC, 3rd ed. (INIMF)
** &trap  trap 
...
Copy the screen output to the file ../trap.fot

See diff_trap.log for the differences of ../trap.log and trap.log
See diff_trap.fot for the differences of ../trap.fot and trap.fot

Step 5. Check the generic font file:
$ gftype trap.72270gf trap.typ
This is GFtype-FPC, 3rd ed.
Mnemonic output? (default=no, ? for help): y
Pixel output? (default=yes, ? for help): y
See diff_trap.typ for the differences of ../trap.typ and trap.typ.

Step 6.
$ tftopl trap.tfm trap.pl
...

The file diff_trap.pl is empty!