test/py: Add tests for the SquashFS commands

Add Python scripts to test 'ls' and 'load' commands. The scripts
generate a SquashFS image and clean the directory after the assertions,
or if an exception is raised.

Signed-off-by: Joao Marcos Costa <joaomarcos.costa@bootlin.com>

test/py/tests/test_fs/test_squashfs/sqfs_common.py

@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020 Bootlin
+# Author: Joao Marcos Costa <joaomarcos.costa@bootlin.com>
+
+import os
+import random
+import string
+
+def sqfs_get_random_letters(size):
+    letters = []
+    for i in range(0, size):
+            letters.append(random.choice(string.ascii_letters))
+
+    return ''.join(letters)
+
+def sqfs_generate_file(path, size):
+    content = sqfs_get_random_letters(size)
+    file = open(path, "w")
+    file.write(content)
+    file.close()
+
+# generate image with three files and a symbolic link
+def sqfs_generate_image():
+    src = "test/py/tests/test_fs/test_squashfs/sqfs_src/"
+    dest = "test/py/tests/test_fs/test_squashfs/sqfs"
+    os.mkdir(src)
+    sqfs_generate_file(src + "frag_only", 100)
+    sqfs_generate_file(src + "blks_frag", 5100)
+    sqfs_generate_file(src + "blks_only", 4096)
+    os.symlink("frag_only", src + "sym")
+    os.system("mksquashfs " + src + " " + dest + " -b 4096 -always-use-fragments")
+
+# removes all files created by sqfs_generate_image()
+def sqfs_clean():
+    src = "test/py/tests/test_fs/test_squashfs/sqfs_src/"
+    dest = "test/py/tests/test_fs/test_squashfs/sqfs"
+    os.remove(src + "frag_only")
+    os.remove(src + "blks_frag")
+    os.remove(src + "blks_only")
+    os.remove(src + "sym")
+    os.rmdir(src)
+    os.remove(dest)