How Client and Server Bots Power Large-Scale MMO Testing

01 Client Bots

Client bots are the most realistic but also the most costly type of bot, requiring separate code derived from the normal client and extensive pruning to reduce maintenance and deployment overhead.

A typical client bot runs without a graphical interface, only a console window, and a well‑configured machine can launch around 200 bots; the original client can only start about six. Even with these limits, the total number of client bots that can run simultaneously is far below the thousands needed for large‑scale events.

Overview

Client bots need an independent codebase modified from the game client, with unnecessary features stripped away. They are used to simulate real player behavior in scenarios such as chat and combat, where true client interaction is required.

Applicable Scenarios

All testing scenarios can theoretically use client bots, but they are essential for chat (which requires broadcasting messages to many clients) and combat (where server‑side bot logic would otherwise affect performance and deviate from real conditions).

Usage and Operations

Client bots are packaged and deployed to multiple test machines, each launching several bot instances that connect to the target server. Build slaves control the whole process, and bots can be run on Linux via Wine.

Maintaining client bot code is cumbersome: for each game version, a separate bot code branch must be prepared, merged, and compiled, often requiring manual conflict resolution.

To achieve realistic load, bot accounts are created in the database with equipment, appearance, and other attributes that closely mimic real players.

02 Server Bots

Server bots are lighter weight because they lack a real client; they exist as server‑side entities created by modifying login functions to spawn new or existing characters near a specified location.

Overview

Server bots can either create new characters or log in existing ones from the database, allowing functional testing without the overhead of a full client.

Usage and Operations

Since server bots have no client, they are simpler to maintain and can be used for most scenarios, including large‑scale activities such as matchmaking, entry, settlement, exit, and reward distribution.

Examples

For large events, server bots verify player counts, queue positions, matchmaking rules, scoreboard updates, boss combat balance, settlement RPC limits, and reward correctness. They have uncovered issues like reversed queue scores, missing special rewards, and matchmaking logic errors.

In probability tests (e.g., treasure‑box drop rates), thousands of server bots can simulate billions of openings by batching item usage and aggregating results.

03 Additional Details

Advanced techniques include batch login across multiple scenes, simulating external player characters by populating a test database with fully grown accounts, and aggregating messages to a master process for coordinated operations such as mass guild creation.

Batch login replaces player‑dependent commands with scene‑wide commands, allowing thousands of bots to be spawned in minutes.

Simulating external roles involves creating a long‑term test database, using GM commands to level up characters, equip them, assign professions, and set temporary states before tests.

Message aggregation solves coordination problems by collecting player IDs, factions, and other data from individual gas processes to the master process, enabling efficient bulk operations.

04 Summary

Beyond stress testing, bots play a crucial role in functional testing for MMOs, handling tasks ranging from large‑scale exploration to probability verification and matchmaking validation. Their use evolves through collaboration between QA and development teams, continuously improving test coverage and reliability.