test: add koji hub plugin unit test skeleton

Load the module, mock session and kojihub, check basic calling
osbuildImage will result in `kojihub.make_task` with the right
parameters.

test/unit/test_hub.py

@@ -0,0 +1,63 @@
+#
+# koji hub plugin unit tests
+#
+
+
+import unittest
+import os
+import imp
+from flexmock import flexmock
+
+
+class TestHubPlugin(unittest.TestCase):
+    def setUp(self):
+        """Loads the plugin to self.plugin"""
+        root = os.getenv("GITHUB_WORKSPACE", os.getcwd())
+
+        haystack = os.path.join(root, "plugins", "hub")
+
+        fp, path, desc = imp.find_module("osbuild", [haystack])
+        try:
+            self.plugin = imp.load_module("osbuild", fp, path, desc)
+        finally:
+            fp.close()
+
+    @staticmethod
+    def mock_koji_context(*, admin=False):
+        session = flexmock()
+        session.should_receive("hasPerm") \
+               .with_args("admin") \
+               .and_return(admin)
+
+        session.should_receive("assertPerm") \
+               .with_args("image") \
+               .once()
+
+        context = flexmock(session=session)
+        return context
+
+    @staticmethod
+    def mock_kojihub(args, task):
+        kojihub = flexmock()
+        kojihub.should_receive("make_task") \
+               .with_args("osbuildImage", args, **task)
+        return kojihub
+
+    def test_basic(self):
+        context = self.mock_koji_context()
+
+        opts = {}
+        args = ["name", "version", "distro",
+                ["image_type"],
+                "target",
+                ["arches"],
+                opts]
+
+        task = {"channel": "image"}
+
+        kojihub = self.mock_kojihub(args, task)
+
+        setattr(self.plugin, "context", context)
+        setattr(self.plugin, "kojihub", kojihub)
+
+        self.plugin.osbuildImage(*args, opts)