Add some docstrings to tests

test/mtp_prop_gen.erl

-%% Common data generators for property-based tests
+%% @doc Common data generators for property-based tests
 
 -module(mtp_prop_gen).
 -include_lib("proper/include/proper.hrl").

test/mtp_test_client.erl

+%% @doc Simple mtproto proxy client
 -module(mtp_test_client).
 
 -export([connect/5,

test/mtp_test_metric.erl

+%% @doc simple metric backend to be used in tests.
+%% XXX: DON'T USE IN PRODUCTION! It can become bottleneck!
 -module(mtp_test_metric).
 
 -behaviour(gen_server).

test/mtp_test_middle_server.erl

-%% Fake telegram "middle-proxy" server
+%% @doc Fake telegram "middle-proxy" server
 -module(mtp_test_middle_server).
 -behaviour(ranch_protocol).
 -behaviour(gen_statem).

test/prop_mtp_abridged.erl

+%% @doc Property-based tests for mtp_abridged
 -module(prop_mtp_abridged).
 -include_lib("proper/include/proper.hrl").
 

test/prop_mtp_aes_cbc.erl

+%% @doc Property-based tests for mtp_aes_cbc
 -module(prop_mtp_aes_cbc).
 -include_lib("proper/include/proper.hrl").
 

test/prop_mtp_full.erl

+%% @doc property-based tests for mtp_full
 -module(prop_mtp_full).
 -include_lib("proper/include/proper.hrl").
 

test/prop_mtp_intermediate.erl

+%% @doc property-based tests for mtp_intermediate
 -module(prop_mtp_intermediate).
 -include_lib("proper/include/proper.hrl").
 

test/prop_mtp_obfuscated.erl

+%% @doc property-based tests for mtp_obfuscated
 -module(prop_mtp_obfuscated).
 -include_lib("proper/include/proper.hrl").
 

test/prop_mtp_rpc.erl

+%% @doc property-based tests for mtp_rpc
 -module(prop_mtp_rpc).
 -include_lib("proper/include/proper.hrl").
 
@@ -63,7 +64,7 @@ s2c_packet(Packet) ->
 
 
 prop_c2s_packet(doc) ->
-    "Tests encode/decode of 'proxy_ans'/'close_ext' RPC packets".
+    "Tests encode/decode of 'data'/'remote_closed' RPC packets".
 
 prop_c2s_packet() ->
     ?FORALL(Packet, c2s_packet_gen(), c2s_packet(Packet)).

test/single_dc_SUITE.erl

-%% Basic tests with only one telegram DC
+%% @doc Basic tests with only one telegram DC
 -module(single_dc_SUITE).
 
 -export([all/0,