oseek="$((ps))" bs=1 count=1
-	atf_check -o inline:"0-$((ps-1)),$((ps+1)) foo" \
+	atf_check dd status=none if="${file}" of=foo \
+	    oseek="$((hs))" bs=1 count=1
+	atf_check -o inline:"0-$((hs-1)),$((hs+1)) foo" \
 	    stat -hn foo
-	atf_check truncate -s "$((ps*3))" foo
-	atf_check -o inline:"0-$((ps-1)),$((ps*2))-$((ps*3-1)) foo" \
+	atf_check truncate -s "$((hs*3))" foo
+	atf_check -o inline:"0-$((hs-1)),$((hs+ps))-$((hs*3-1)) foo" \
 	    stat -hn foo
 
 	# Test multiple files.
-	atf_check dd status=none if=/COPYRIGHT of=bar
+	atf_check dd status=none if="${file}" of=bar
 	sz=$(stat -f%z bar)
-	atf_check -o inline:"0-$((ps-1)),$((ps*2))-$((ps*3-1)) foo
-$((sz)) bar
-" \
+	atf_check -o inline:"0-$((hs-1)),$((hs+ps))-$((hs*3-1)) foo\n$((sz)) bar\n" \
 	    stat -h foo bar
 
 	# For a device, fail.