vhd-tool: Add cram tests for read_headers

This is just an easy way to make sure the semantics are preserved in any
future refactorings, without having to run full VHD exports.

Signed-off-by: Andrii Sultanov <andriy.sultanov@vates.tech>

Author: last-genius

ocaml/vhd-tool/cli/dune

@@ -71,3 +71,7 @@
   (section libexec_root)
   (files (get_vhd_vsize.exe as xapi/get_vhd_vsize) (sparse_dd.exe as xapi/sparse_dd))
 )
+
+(cram
+ (package vhd-tool)
+ (deps main.exe))

ocaml/vhd-tool/cli/read_headers.t

@@ -0,0 +1,22 @@
+Create a sparse raw file
+  $ dd if=/dev/random of=test.raw bs=2097152 count=16 > /dev/null 2>&1
+  $ dd if=/dev/zero of=test.raw bs=2097152 count=10 seek=3 conv=notrunc > /dev/null 2>&1
+
+Convert to .vhd
+  $ qemu-img convert -f raw -O vpc test.raw test.vhd
+
+Check if the right clusters are found to be allocated (legacy JSON format)
+  $ ./main.exe read_headers test.vhd
+  {"virtual_size":33562624,"cluster_bits":21,"data_clusters":[0,1,2,13,14,15]}
+
+Check fully allocated file
+  $ dd if=/dev/random of=test.raw bs=2097152 count=16 > /dev/null 2>&1
+  $ qemu-img convert -f raw -O vpc test.raw test.vhd
+  $ ./main.exe read_headers test.vhd
+  {"virtual_size":33562624,"cluster_bits":21,"data_clusters":[0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]}
+
+Check empty file
+  $ dd if=/dev/zero of=test.raw bs=2097152 count=16 > /dev/null 2>&1
+  $ qemu-img convert -f raw -O vpc test.raw test.vhd
+  $ ./main.exe read_headers test.vhd
+  {"virtual_size":33562624,"cluster_bits":21,"data_clusters":[]}