diff --git a/avocado/utils/disk.py b/avocado/utils/disk.py
index 4034addcc2d9c5513f5c504b1820065abdef3f3e..2cb9b787ff489976383cca113240c06f9604709a 100644
--- a/avocado/utils/disk.py
+++ b/avocado/utils/disk.py
@@ -24,6 +24,7 @@ Disk utilities
 
 import os
 import json
+
 from . import process
 
 
@@ -39,6 +40,18 @@ def get_disk_blocksize(path):
 
 
 def get_disks():
+    """
+    Returns the physical "hard drives" available on this system
+
+    This is a simple wrapper around `lsblk` and will return all the
+    top level physical (non-virtual) devices return by it.
+
+    TODO: this is currently Linux specific.  Support for other
+    platforms is desirable and may be implemented in the future.
+
+    :returns: a list of paths to the physical disks on the system
+    :rtype: list of str
+    """
     json_result = process.run('lsblk --json')
     json_data = json.loads(json_result.stdout_text)
     return ['/dev/%s' % str(disk['name']) for disk in json_data['blockdevices']]
diff --git a/selftests/unit/test_utils_disk.py b/selftests/unit/test_utils_disk.py
new file mode 100644
index 0000000000000000000000000000000000000000..919eb739a59bcf0d928881758cc26e12e02e50b6
--- /dev/null
+++ b/selftests/unit/test_utils_disk.py
@@ -0,0 +1,47 @@
+import unittest
+
+try:
+    from unittest import mock
+except ImportError:
+    import mock
+
+
+from avocado.utils import disk
+from avocado.utils import process
+
+
+class Disk(unittest.TestCase):
+
+    LSBLK_OUTPUT = b'''
+{
+   "blockdevices": [
+      {"name": "vda", "maj:min": "252:0", "rm": "0", "size": "6G", "ro": "0", "type": "disk", "mountpoint": null,
+         "children": [
+            {"name": "vda1", "maj:min": "252:1", "rm": "0", "size": "1M", "ro": "0", "type": "part", "mountpoint": null},
+            {"name": "vda2", "maj:min": "252:2", "rm": "0", "size": "1G", "ro": "0", "type": "part", "mountpoint": "/boot"},
+            {"name": "vda3", "maj:min": "252:3", "rm": "0", "size": "615M", "ro": "0", "type": "part", "mountpoint": "[SWAP]"},
+            {"name": "vda4", "maj:min": "252:4", "rm": "0", "size": "4.4G", "ro": "0", "type": "part", "mountpoint": "/"}
+         ]
+      }
+   ]
+}'''
+
+    def test_empty(self):
+        mock_result = process.CmdResult(
+            command='lsblk --json',
+            stdout=b'{"blockdevices": []}')
+        with mock.patch('avocado.utils.disk.process.run',
+                        return_value=mock_result):
+            self.assertEqual(disk.get_disks(), [])
+
+    def test_disks(self):
+        mock_result = process.CmdResult(
+            command='lsblk --json',
+            stdout=self.LSBLK_OUTPUT)
+        with mock.patch('avocado.utils.disk.process.run',
+                        return_value=mock_result):
+            self.assertEqual(disk.get_disks(), ['/dev/vda'])
+
+
+if __name__ == '__main__':
+    unittest.main()