Add some completion tests.

test/completion/completion.py

@@ -0,0 +1,26 @@
+"""
+Special cases of completions (typically special positions that caused issues
+with context parsing.
+"""
+
+def pass_decorator(func):
+    return func
+
+
+def x():
+    return (
+        1,
+#? ["tuple"]
+tuple
+    )
+
+    # Comment just somewhere
+
+
+class MyClass:
+    @pass_decorator
+    def x(foo,
+#? 5 ["tuple"]
+tuple,
+          ):
+        return 1