yosys/tests/various/rtlil_z_bits.ys

! mkdir -p temp
read_rtlil <<EOT
module \test
  wire output 1 \a
  connect \a 1'z
end
EOT
write_rtlil temp/rtlil_z_bits.il
! grep -F -q "connect \\a 1'z" temp/rtlil_z_bits.il