Add functional/acceptance tests infrastructure

This patch adds the very minimum infrastructure necessary for writing
and running functional/acceptance tests, including:

 * Documentation
 * The avocado_qemu.Test base test class
 * One example tests (version.py)

Additional functionality is expected to be added along the tests that
require them.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Message-Id: <20180530184156.15634-2-crosa@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
[ehabkost: fix typo on testing.rst]
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

tests/acceptance/avocado_qemu/__init__.py

@@ -0,0 +1,54 @@
+# Test class and utilities for functional tests
+#
+# Copyright (c) 2018 Red Hat, Inc.
+#
+# Author:
+#  Cleber Rosa <crosa@redhat.com>
+#
+# This work is licensed under the terms of the GNU GPL, version 2 or
+# later.  See the COPYING file in the top-level directory.
+
+import os
+import sys
+
+import avocado
+
+SRC_ROOT_DIR = os.path.dirname(os.path.dirname(os.path.dirname(__file__)))
+SRC_ROOT_DIR = os.path.abspath(os.path.dirname(SRC_ROOT_DIR))
+sys.path.append(os.path.join(SRC_ROOT_DIR, 'scripts'))
+
+from qemu import QEMUMachine
+
+def is_readable_executable_file(path):
+    return os.path.isfile(path) and os.access(path, os.R_OK | os.X_OK)
+
+
+def pick_default_qemu_bin():
+    """
+    Picks the path of a QEMU binary, starting either in the current working
+    directory or in the source tree root directory.
+    """
+    arch = os.uname()[4]
+    qemu_bin_relative_path = os.path.join("%s-softmmu" % arch,
+                                          "qemu-system-%s" % arch)
+    if is_readable_executable_file(qemu_bin_relative_path):
+        return qemu_bin_relative_path
+
+    qemu_bin_from_src_dir_path = os.path.join(SRC_ROOT_DIR,
+                                              qemu_bin_relative_path)
+    if is_readable_executable_file(qemu_bin_from_src_dir_path):
+        return qemu_bin_from_src_dir_path
+
+
+class Test(avocado.Test):
+    def setUp(self):
+        self.vm = None
+        self.qemu_bin = self.params.get('qemu_bin',
+                                        default=pick_default_qemu_bin())
+        if self.qemu_bin is None:
+            self.cancel("No QEMU binary defined or found in the source tree")
+        self.vm = QEMUMachine(self.qemu_bin)
+
+    def tearDown(self):
+        if self.vm is not None:
+            self.vm.shutdown()