enforce a stable list order when attaching/detaching instance groups

awx/main/tests/functional/test_instance_group_ordering.py

@@ -0,0 +1,102 @@
+import pytest
+
+from awx.main.models import InstanceGroup
+
+
+@pytest.fixture(scope='function')
+def source_model(request):
+    return request.getfixturevalue(request.param)
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    'source_model', ['job_template', 'inventory', 'organization'], indirect=True
+)
+def test_instance_group_ordering(source_model):
+    groups = [
+        InstanceGroup.objects.create(name='host-%d' % i)
+        for i in range(5)
+    ]
+    groups.reverse()
+    for group in groups:
+        source_model.instance_groups.add(group)
+
+    assert [g.name for g in source_model.instance_groups.all()] == [
+        'host-4', 'host-3', 'host-2', 'host-1', 'host-0'
+    ]
+    assert [
+        (row.position, row.instancegroup.name)
+        for row in source_model.instance_groups.through.objects.all()
+    ] == [
+        (0, 'host-4'),
+        (1, 'host-3'),
+        (2, 'host-2'),
+        (3, 'host-1'),
+        (4, 'host-0'),
+    ]
+
+    source_model.instance_groups.remove(groups[0])
+    assert [g.name for g in source_model.instance_groups.all()] == [
+        'host-3', 'host-2', 'host-1', 'host-0'
+    ]
+    assert [
+        (row.position, row.instancegroup.name)
+        for row in source_model.instance_groups.through.objects.all()
+    ] == [
+        (0, 'host-3'),
+        (1, 'host-2'),
+        (2, 'host-1'),
+        (3, 'host-0'),
+    ]
+
+    source_model.instance_groups.clear()
+    assert source_model.instance_groups.through.objects.count() == 0
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    'source_model', ['job_template', 'inventory', 'organization'], indirect=True
+)
+def test_instance_group_middle_deletion(source_model):
+    groups = [
+        InstanceGroup.objects.create(name='host-%d' % i)
+        for i in range(5)
+    ]
+    groups.reverse()
+    for group in groups:
+        source_model.instance_groups.add(group)
+
+    source_model.instance_groups.remove(groups[2])
+    assert [g.name for g in source_model.instance_groups.all()] == [
+        'host-4', 'host-3', 'host-1', 'host-0'
+    ]
+    assert [
+        (row.position, row.instancegroup.name)
+        for row in source_model.instance_groups.through.objects.all()
+    ] == [
+        (0, 'host-4'),
+        (1, 'host-3'),
+        (2, 'host-1'),
+        (3, 'host-0'),
+    ]
+
+
+@pytest.mark.django_db
+@pytest.mark.parametrize(
+    'source_model', ['job_template', 'inventory', 'organization'], indirect=True
+)
+def test_explicit_ordering(source_model):
+    groups = [
+        InstanceGroup.objects.create(name='host-%d' % i)
+        for i in range(5)
+    ]
+    groups.reverse()
+    for group in groups:
+        source_model.instance_groups.add(group)
+
+    assert [g.name for g in source_model.instance_groups.all()] == [
+        'host-4', 'host-3', 'host-2', 'host-1', 'host-0'
+    ]
+    assert [g.name for g in source_model.instance_groups.order_by('name').all()] == [
+        'host-0', 'host-1', 'host-2', 'host-3', 'host-4'
+    ]