tests: od: verify -t f defaults to double precision

* tests/od/od.pl: Add tests to ensure -t f (no size suffix) defaults
to double precision (8 bytes), matching -t fD, and differs from -t fF
(explicit 4-byte float).
uutils/coreutils#11396

Author: sylvestre

tests/od/od.pl

@@ -99,6 +99,18 @@
       {ERR=>"$prog: invalid -w argument '-1'\n"}],
      ['invalid-w-3',   '-ww -An', {IN=>""}, {EXIT=>1},
       {ERR=>"$prog: invalid -w argument 'w'\n"}],
+
+     # Ensure -t f defaults to double precision (8 bytes), not float (4 bytes).
+     # https://github.com/uutils/coreutils/pull/11396
+     ['tf-default', '-An -t f',
+      {IN_PIPE=>"\x00\x00\x80\x3f\x00\x00\x00\x40"},
+      {OUT=>"        2.000000473111868\n"}],
+     ['tf-double', '-An -t fD',
+      {IN_PIPE=>"\x00\x00\x80\x3f\x00\x00\x00\x40"},
+      {OUT=>"        2.000000473111868\n"}],
+     ['tf-float', '-An -t fF',
+      {IN_PIPE=>"\x00\x00\x80\x3f\x00\x00\x00\x40"},
+      {OUT=>"               1               2\n"}],
     );
 
 my $save_temps = $ENV{DEBUG};