Add tests for layer renaming

Could have an own file for each test, but this is good enough.
With great help from @dfelinto, thanks!

tests/python/render_layer/test_collection_rename.py

@@ -0,0 +1,79 @@
+# ./blender.bin --background -noaudio --python tests/python/render_layer/test_collection_rename.py -- --testdir="/data/lib/tests/"
+
+# ############################################################
+# Importing - Same For All Render Layer Tests
+# ############################################################
+
+import unittest
+
+import os, sys
+sys.path.append(os.path.dirname(__file__))
+
+from render_layer_common import *
+
+
+# ############################################################
+# Testing
+# ############################################################
+
+class UnitTesting(RenderLayerTesting):
+    def setup_family(self):
+        import bpy
+        scene = bpy.context.scene
+
+        # Just add a bunch of collections on which we can do various tests.
+        grandma = scene.master_collection.collections.new('grandma')
+        grandpa = scene.master_collection.collections.new('grandpa')
+        mom = grandma.collections.new('mom')
+        son = mom.collections.new('son')
+        daughter = mom.collections.new('daughter')
+        uncle = grandma.collections.new('uncle')
+        cousin = uncle.collections.new('cousin')
+
+        lookup = {c.name: c for c in (grandma, grandpa, mom, son, daughter, uncle, cousin)}
+        return lookup
+
+    def test_rename_a(self):
+        family = self.setup_family()
+
+        family['mom'].name = family['daughter'].name
+        self.assertNotEqual(family['mom'].name, family['daughter'].name)
+
+    def test_rename_b(self):
+        family = self.setup_family()
+
+        family['grandma'].name = family['grandpa'].name
+        self.assertNotEqual(family['grandma'].name, family['grandpa'].name)
+
+
+    def test_rename_c(self):
+        family = self.setup_family()
+
+        family['cousin'].name = family['daughter'].name
+        self.assertNotEqual(family['cousin'].name, family['daughter'].name)
+
+    def test_rename_d(self):
+        family = self.setup_family()
+
+        family['son'].name = family['daughter'].name
+        self.assertNotEqual(family['son'].name, family['daughter'].name)
+
+    def test_add_equal_name(self):
+        family = self.setup_family()
+
+        family['mom'].collections.new('daughter')
+        self.assertNotEqual(family['mom'].name, family['daughter'].name)
+
+
+# ############################################################
+# Main - Same For All Render Layer Tests
+# ############################################################
+
+if __name__ == '__main__':
+    import sys
+
+    extra_arguments = sys.argv[sys.argv.index("--") + 1:] if "--" in sys.argv else []
+    sys.argv = [__file__] + (sys.argv[sys.argv.index("--") + 2:] if "--" in sys.argv else [])
+
+    UnitTesting._extra_arguments = extra_arguments
+    unittest.main()