tests.acceptance: adds multi vm capability for acceptance tests

This change adds the possibility to write acceptance tests with multi
virtual machine support. It's done keeping the virtual machines objects
stored in a test attribute (dictionary). This dictionary shouldn't be
accessed directly but through the new method added `get_vm`. This new
method accept a list of args (that will be added as virtual machine
arguments) and an optional name argument. The name is the key that
identify a single virtual machine along the test machines available. If
a name without a machine is informed a new machine will be instantiated.

The current usage of vm in tests will not be broken by this change since
it keeps a property called vm in the base test class. This property only
calls the new method `get_vm` with default parameters (no args and
'default' as machine name).

Signed-off-by: Caio Carrara <ccarrara@redhat.com>
Reviewed-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Wainer dos Santos Moschetta <wainersm@redhat.com>
Message-Id: <20190212193855.13223-2-ccarrara@redhat.com>
Signed-off-by: Cleber Rosa <crosa@redhat.com>

docs/devel/testing.rst

@@ -633,7 +633,46 @@ instance, available at ``self.vm``.  Because many tests will tweak the
 QEMU command line, launching the QEMUMachine (by using ``self.vm.launch()``)
 is left to the test writer.
 
-At test "tear down", ``avocado_qemu.Test`` handles the QEMUMachine
+The base test class has also support for tests with more than one
+QEMUMachine. The way to get machines is through the ``self.get_vm()``
+method which will return a QEMUMachine instance. The ``self.get_vm()``
+method accepts arguments that will be passed to the QEMUMachine creation
+and also an optional `name` attribute so you can identify a specific
+machine and get it more than once through the tests methods. A simple
+and hypothetical example follows:
+
+.. code::
+
+  from avocado_qemu import Test
+
+
+  class MultipleMachines(Test):
+      """
+      :avocado: enable
+      """
+      def test_multiple_machines(self):
+          first_machine = self.get_vm()
+          second_machine = self.get_vm()
+          self.get_vm(name='third_machine').launch()
+
+          first_machine.launch()
+          second_machine.launch()
+
+          first_res = first_machine.command(
+              'human-monitor-command',
+              command_line='info version')
+
+          second_res = second_machine.command(
+              'human-monitor-command',
+              command_line='info version')
+
+          third_res = self.get_vm(name='third_machine').command(
+              'human-monitor-command',
+              command_line='info version')
+
+          self.assertEquals(first_res, second_res, third_res)
+
+At test "tear down", ``avocado_qemu.Test`` handles all the QEMUMachines
 shutdown.
 
 QEMUMachine

tests/acceptance/avocado_qemu/__init__.py

@@ -10,6 +10,7 @@
 
 import os
 import sys
+import uuid
 
 import avocado
 
@@ -41,13 +42,29 @@ def pick_default_qemu_bin():
 
 class Test(avocado.Test):
     def setUp(self):
-        self.vm = None
+        self._vms = {}
         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 _new_vm(self, *args):
+        vm = QEMUMachine(self.qemu_bin)
+        if args:
+            vm.add_args(*args)
+        return vm
+
+    @property
+    def vm(self):
+        return self.get_vm(name='default')
+
+    def get_vm(self, *args, name=None):
+        if not name:
+            name = str(uuid.uuid4())
+        if self._vms.get(name) is None:
+            self._vms[name] = self._new_vm(*args)
+        return self._vms[name]
 
     def tearDown(self):
-        if self.vm is not None:
-            self.vm.shutdown()
+        for vm in self._vms.values():
+            vm.shutdown()