feat: Add initial implementation of CI/CD workflows, documentation, and testing framework

.config/dotnet-tools.json

@@ -0,0 +1,12 @@
+{
+  "version": 1,
+  "isRoot": true,
+  "tools": {
+    "docfx": {
+      "version": "2.78.3",
+      "commands": [
+        "docfx"
+      ]
+    }
+  }
+}

.github/workflows/ci-release.yml

@@ -0,0 +1,177 @@
+name: CI / Release / Docs
+
+on:
+  push:
+    branches: [master]
+
+permissions:
+  contents: write
+
+jobs:
+  lint-markdown:
+    name: Markdown Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Run markdownlint-cli2
+        uses: DavidAnson/markdownlint-cli2-action@v19
+        with:
+          globs: |
+            **/*.md
+            !.dev/**
+            !docs/api/**
+            !**/node_modules/**
+            !**/bin/**
+            !**/obj/**
+
+  detect-changes:
+    name: Detect Changes
+    runs-on: ubuntu-latest
+    outputs:
+      src_changed: ${{ steps.check.outputs.src_changed }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 2
+
+      - name: Check for src/ changes
+        id: check
+        run: |
+          CHANGED=$(git diff --name-only HEAD~1 HEAD -- 'src/' | wc -l)
+          if [ "$CHANGED" -gt 0 ]; then
+            echo "src_changed=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "src_changed=false" >> "$GITHUB_OUTPUT"
+          fi
+
+  test:
+    name: Build & Test
+    needs: [lint-markdown, detect-changes]
+    if: needs.detect-changes.outputs.src_changed == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET 10
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Restore dependencies
+        run: dotnet restore src/EchoHub.slnx
+
+      - name: Build
+        run: dotnet build src/EchoHub.slnx --no-restore --configuration Release
+
+      - name: Test
+        run: dotnet test src/EchoHub.slnx --no-build --configuration Release --verbosity normal
+
+  release:
+    name: Create Release
+    needs: [lint-markdown, detect-changes, test]
+    if: needs.detect-changes.outputs.src_changed == 'true'
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET 10
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Read version
+        id: version
+        run: |
+          VERSION=$(grep -oP '(?<=<Version>)[^<]+' src/Directory.Build.props)
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+          echo "tag=v$VERSION" >> "$GITHUB_OUTPUT"
+
+      - name: Check if release exists
+        id: check_release
+        run: |
+          if gh release view "${{ steps.version.outputs.tag }}" &>/dev/null; then
+            echo "exists=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "exists=false" >> "$GITHUB_OUTPUT"
+          fi
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Publish Server win-x64
+        if: steps.check_release.outputs.exists == 'false'
+        run: dotnet publish src/EchoHub.Server/EchoHub.Server.csproj -c Release -r win-x64 --self-contained true -o publish/server-win-x64
+
+      - name: Publish Server linux-x64
+        if: steps.check_release.outputs.exists == 'false'
+        run: dotnet publish src/EchoHub.Server/EchoHub.Server.csproj -c Release -r linux-x64 --self-contained true -o publish/server-linux-x64
+
+      - name: Publish Server osx-x64
+        if: steps.check_release.outputs.exists == 'false'
+        run: dotnet publish src/EchoHub.Server/EchoHub.Server.csproj -c Release -r osx-x64 --self-contained true -o publish/server-osx-x64
+
+      - name: Publish Client win-x64
+        if: steps.check_release.outputs.exists == 'false'
+        run: dotnet publish src/EchoHub.Client/EchoHub.Client.csproj -c Release -r win-x64 --self-contained true -o publish/client-win-x64
+
+      - name: Publish Client linux-x64
+        if: steps.check_release.outputs.exists == 'false'
+        run: dotnet publish src/EchoHub.Client/EchoHub.Client.csproj -c Release -r linux-x64 --self-contained true -o publish/client-linux-x64
+
+      - name: Publish Client osx-x64
+        if: steps.check_release.outputs.exists == 'false'
+        run: dotnet publish src/EchoHub.Client/EchoHub.Client.csproj -c Release -r osx-x64 --self-contained true -o publish/client-osx-x64
+
+      - name: Zip artifacts
+        if: steps.check_release.outputs.exists == 'false'
+        run: |
+          cd publish
+          zip -r ../EchoHub-Server-win-x64.zip server-win-x64/
+          zip -r ../EchoHub-Server-linux-x64.zip server-linux-x64/
+          zip -r ../EchoHub-Server-osx-x64.zip server-osx-x64/
+          zip -r ../EchoHub-Client-win-x64.zip client-win-x64/
+          zip -r ../EchoHub-Client-linux-x64.zip client-linux-x64/
+          zip -r ../EchoHub-Client-osx-x64.zip client-osx-x64/
+
+      - name: Create GitHub Release
+        if: steps.check_release.outputs.exists == 'false'
+        run: |
+          gh release create "${{ steps.version.outputs.tag }}" \
+            --title "EchoHub ${{ steps.version.outputs.tag }}" \
+            --generate-notes \
+            EchoHub-Server-win-x64.zip \
+            EchoHub-Server-linux-x64.zip \
+            EchoHub-Server-osx-x64.zip \
+            EchoHub-Client-win-x64.zip \
+            EchoHub-Client-linux-x64.zip \
+            EchoHub-Client-osx-x64.zip
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+  docs:
+    name: Build & Deploy Docs
+    needs: lint-markdown
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup .NET 10
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Restore .NET tools
+        run: dotnet tool restore
+
+      - name: Build solution
+        run: dotnet build src/EchoHub.slnx --configuration Release
+
+      - name: Generate documentation
+        run: dotnet docfx docs/docfx.json
+
+      - name: Deploy to web branch
+        uses: peaceiris/actions-gh-pages@v4
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./docs/_site
+          publish_branch: web

.github/workflows/pr-check.yml

@@ -0,0 +1,65 @@
+name: PR Check
+
+on:
+  pull_request:
+    branches: [master]
+
+jobs:
+  lint-markdown:
+    name: Markdown Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Run markdownlint-cli2
+        uses: DavidAnson/markdownlint-cli2-action@v19
+        with:
+          globs: |
+            **/*.md
+            !.dev/**
+            !docs/api/**
+            !**/node_modules/**
+            !**/bin/**
+            !**/obj/**
+
+  test:
+    name: Build & Test
+    needs: lint-markdown
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Check for src/ changes
+        id: changes
+        run: |
+          git fetch origin ${{ github.base_ref }} --depth=1
+          CHANGED=$(git diff --name-only origin/${{ github.base_ref }}...HEAD -- 'src/' | wc -l)
+          if [ "$CHANGED" -gt 0 ]; then
+            echo "src_changed=true" >> "$GITHUB_OUTPUT"
+          else
+            echo "src_changed=false" >> "$GITHUB_OUTPUT"
+          fi
+
+      - name: Setup .NET 10
+        if: steps.changes.outputs.src_changed == 'true'
+        uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '10.0.x'
+
+      - name: Restore dependencies
+        if: steps.changes.outputs.src_changed == 'true'
+        run: dotnet restore src/EchoHub.slnx
+
+      - name: Build
+        if: steps.changes.outputs.src_changed == 'true'
+        run: dotnet build src/EchoHub.slnx --no-restore --configuration Release
+
+      - name: Test
+        if: steps.changes.outputs.src_changed == 'true'
+        run: dotnet test src/EchoHub.slnx --no-build --configuration Release --verbosity normal
+
+      - name: Skip notice
+        if: steps.changes.outputs.src_changed == 'false'
+        run: echo "No changes in src/ — skipping build and test"

.gitignore

@@ -429,3 +429,8 @@ CLAUDE.md
 *.db-*
 src/EchoHub.Server/uploads/*
 .claude/*
+
+# DocFx generated output
+docs/_site/
+docs/api/
+!docs/api/.gitkeep

.markdownlint-cli2.jsonc

@@ -0,0 +1,14 @@
+{
+  "config": {
+    "MD013": false,
+    "MD033": false,
+    "MD041": false
+  },
+  "ignores": [
+    ".dev/**",
+    "docs/api/**",
+    "**/node_modules/**",
+    "**/bin/**",
+    "**/obj/**"
+  ]
+}

README.md

@@ -76,7 +76,7 @@ graph TD
 ### Client
 
 - **Runs in your terminal** — no browser, no Electron, no 500MB of bundled Chromium
-- **6 built-in themes** — including `hacker` for when you want to feel like you're in a movie
+- **13 built-in themes** — including `hacker` for when you want to feel like you're in a movie
 - **Slash commands** — `/join`, `/send`, `/status`, `/theme`, etc.
 - **Colored nicknames** — pick your hex color, express yourself
 - **File/image sharing** — local files or URLs
@@ -151,6 +151,13 @@ dotnet build src/EchoHub.slnx
 | `light` | Black on white — for the brave |
 | `hacker` | Green on black — *I'm in* |
 | `solarized` | Cyan/yellow on dark gray — for the refined |
+| `dracula` | Purple accents on black — the classic dark theme |
+| `monokai` | Yellow highlights on black — warm and familiar |
+| `nord` | Cool blues — arctic vibes |
+| `gruvbox` | Earthy yellows on black — retro warmth |
+| `ocean` | Cyan on deep blue — underwater aesthetics |
+| `highcontrast` | Bright yellow on black — maximum readability |
+| `rosepine` | Muted pinks on black — cozy and soft |
 
 ## Configuration
 

docs/articles/architecture.md

@@ -0,0 +1,41 @@
+# Architecture
+
+## Overview
+
+EchoHub follows a decentralized model where each server is fully independent. There is no central authority or account federation. Users create one account per server.
+
+## Components
+
+### EchoHub.Core
+
+Shared library containing:
+
+- **Models**: `User`, `Channel`, `Message`, `RefreshToken`
+- **DTOs**: Record types for API requests/responses
+- **Contracts**: `IEchoHubClient` -- the strongly-typed SignalR client interface
+- **Constants**: `ValidationConstants` (shared regex patterns), `HubConstants`
+
+### EchoHub.Server
+
+ASP.NET Core web application:
+
+- **Controllers**: REST API endpoints for auth, channels, users, files, server info
+- **Hubs**: SignalR `ChatHub` for real-time messaging
+- **Auth**: JWT token service (15-min access tokens, 30-day refresh tokens)
+- **Data**: EF Core with SQLite
+- **Services**: Presence tracking, file storage, image-to-ASCII conversion
+
+### EchoHub.Client
+
+Terminal.Gui v2 TUI application:
+
+- **UI**: Main window, dialogs, chat renderer with ANSI color support
+- **Services**: API client with automatic token refresh, SignalR connection wrapper
+- **Themes**: 6 built-in color themes
+- **Config**: Client configuration management
+
+## Communication
+
+- REST API for authentication, profile management, channel CRUD, file uploads
+- SignalR WebSocket for real-time messaging and presence updates
+- JWT tokens passed via query string for SignalR authentication

docs/articles/getting-started.md

@@ -0,0 +1,31 @@
+# Getting Started
+
+## Prerequisites
+
+- [.NET 10 SDK](https://dotnet.microsoft.com/download)
+
+## Run the Server
+
+```bash
+dotnet run --project src/EchoHub.Server
+```
+
+On first run, the server automatically:
+
+1. Creates `appsettings.json` from the example config
+2. Generates a secure JWT secret
+3. Creates the SQLite database with a `#general` channel
+
+## Run the Client
+
+```bash
+dotnet run --project src/EchoHub.Client
+```
+
+Connect to a server, register an account, and start chatting.
+
+## Build from Source
+
+```bash
+dotnet build src/EchoHub.slnx
+```

docs/articles/toc.yml

@@ -0,0 +1,4 @@
+- name: Getting Started
+  href: getting-started.md
+- name: Architecture
+  href: architecture.md

docs/changelog/toc.yml

@@ -0,0 +1,2 @@
+- name: v0.1.0
+  href: v0.1.0.md

docs/changelog/v0.1.0.md

@@ -0,0 +1,13 @@
+# v0.1.0 - Initial Release
+
+## Features
+
+- Real-time messaging via SignalR
+- JWT authentication with access and refresh tokens
+- Channel management (create, set topic, delete)
+- File and image uploads with magic-byte validation
+- Image-to-ASCII conversion for terminal display
+- Presence tracking (online, away, DND, invisible)
+- 6 built-in TUI themes
+- Rate limiting on auth, upload, and general endpoints
+- Self-contained binary releases for Windows, Linux, and macOS

docs/docfx.json

@@ -0,0 +1,55 @@
+{
+  "metadata": [
+    {
+      "src": [
+        {
+          "src": "../src",
+          "files": [
+            "EchoHub.Core/EchoHub.Core.csproj",
+            "EchoHub.Server/EchoHub.Server.csproj",
+            "EchoHub.Client/EchoHub.Client.csproj"
+          ]
+        }
+      ],
+      "dest": "api",
+      "properties": {
+        "TargetFramework": "net10.0"
+      }
+    }
+  ],
+  "build": {
+    "content": [
+      {
+        "files": [
+          "**/*.{md,yml}"
+        ],
+        "exclude": [
+          "_site/**"
+        ]
+      }
+    ],
+    "resource": [
+      {
+        "files": [
+          "images/**"
+        ]
+      }
+    ],
+    "output": "_site",
+    "template": [
+      "default",
+      "modern"
+    ],
+    "globalMetadata": {
+      "_appName": "EchoHub",
+      "_appTitle": "EchoHub Documentation",
+      "_enableSearch": true,
+      "_disableContribution": false,
+      "_gitContribute": {
+        "repo": "https://github.com/HueByte/EchoHub",
+        "branch": "master"
+      }
+    },
+    "markdownEngineName": "markdig"
+  }
+}

docs/index.md

@@ -0,0 +1,14 @@
+---
+_layout: landing
+---
+
+# EchoHub Documentation
+
+Welcome to the EchoHub documentation. EchoHub is a decentralized, IRC-like chat application built with .NET 10 and SignalR.
+
+## Quick Links
+
+- [Getting Started](articles/getting-started.md) - Set up and run EchoHub
+- [Architecture](articles/architecture.md) - Understand the system design
+- [API Reference](api/index.md) - Generated C# API documentation
+- [Changelog](changelog/v0.1.0.md) - Release history

docs/toc.yml

@@ -0,0 +1,7 @@
+- name: Articles
+  href: articles/
+- name: Changelog
+  href: changelog/
+- name: API Reference
+  href: api/
+  homepage: api/index.md

src/Directory.Build.props

@@ -0,0 +1,5 @@
+<Project>
+  <PropertyGroup>
+    <Version>0.1.0</Version>
+  </PropertyGroup>
+</Project>

src/EchoHub.Client/Themes/ThemeManager.cs

@@ -181,6 +181,237 @@ public static class ThemeManager
         }
     };
 
+    private static readonly Theme DraculaTheme = new()
+    {
+        Name = "Dracula",
+        Base = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "Magenta"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "BrightMagenta",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "BrightMagenta"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "DarkGray",
+            FocusForeground = "Black",
+            FocusBackground = "Magenta"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "BrightMagenta",
+            Background = "Black",
+            FocusForeground = "BrightMagenta",
+            FocusBackground = "Black"
+        }
+    };
+
+    private static readonly Theme MonokaiTheme = new()
+    {
+        Name = "Monokai",
+        Base = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "BrightYellow"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "BrightYellow"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "DarkGray",
+            FocusForeground = "Black",
+            FocusBackground = "BrightYellow"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "BrightYellow",
+            FocusBackground = "Black"
+        }
+    };
+
+    private static readonly Theme NordTheme = new()
+    {
+        Name = "Nord",
+        Base = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "DarkBlue",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "Blue"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "Blue",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "DarkBlue"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "Blue",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "DarkBlue"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "BrightCyan",
+            Background = "DarkBlue",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "DarkBlue"
+        }
+    };
+
+    private static readonly Theme GruvboxTheme = new()
+    {
+        Name = "Gruvbox",
+        Base = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "DarkYellow"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "DarkYellow"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "DarkGray",
+            FocusForeground = "Black",
+            FocusBackground = "DarkYellow"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "DarkYellow",
+            Background = "Black",
+            FocusForeground = "DarkYellow",
+            FocusBackground = "Black"
+        }
+    };
+
+    private static readonly Theme OceanTheme = new()
+    {
+        Name = "Ocean",
+        Base = new ThemeColors
+        {
+            Foreground = "BrightCyan",
+            Background = "DarkBlue",
+            FocusForeground = "White",
+            FocusBackground = "DarkCyan"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "DarkCyan",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "DarkBlue"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "DarkCyan",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "DarkBlue"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "BrightCyan",
+            Background = "DarkCyan",
+            FocusForeground = "BrightCyan",
+            FocusBackground = "DarkCyan"
+        }
+    };
+
+    private static readonly Theme HighContrastTheme = new()
+    {
+        Name = "HighContrast",
+        Base = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "BrightYellow"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "BrightYellow"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "BrightYellow"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "BrightYellow",
+            Background = "Black",
+            FocusForeground = "BrightYellow",
+            FocusBackground = "Black"
+        }
+    };
+
+    private static readonly Theme RosePineTheme = new()
+    {
+        Name = "RosePine",
+        Base = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "Black",
+            FocusForeground = "Black",
+            FocusBackground = "DarkMagenta"
+        },
+        Menu = new ThemeColors
+        {
+            Foreground = "Magenta",
+            Background = "Black",
+            FocusForeground = "White",
+            FocusBackground = "DarkMagenta"
+        },
+        Dialog = new ThemeColors
+        {
+            Foreground = "White",
+            Background = "DarkGray",
+            FocusForeground = "White",
+            FocusBackground = "DarkMagenta"
+        },
+        Status = new ThemeColors
+        {
+            Foreground = "Magenta",
+            Background = "Black",
+            FocusForeground = "Magenta",
+            FocusBackground = "Black"
+        }
+    };
+
     private static readonly Theme TransparentTheme = new()
     {
         Name = "Transparent",
@@ -221,7 +452,14 @@ public static class ThemeManager
         ClassicTheme,
         LightTheme,
         HackerTheme,
-        SolarizedTheme
+        SolarizedTheme,
+        DraculaTheme,
+        MonokaiTheme,
+        NordTheme,
+        GruvboxTheme,
+        OceanTheme,
+        HighContrastTheme,
+        RosePineTheme
     ];
 
     public static List<Theme> GetAvailableThemes()

src/EchoHub.Tests/EchoHub.Tests.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.*" />
+    <PackageReference Include="xunit" Version="2.*" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.*">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\EchoHub.Core\EchoHub.Core.csproj" />
+    <ProjectReference Include="..\EchoHub.Server\EchoHub.Server.csproj" />
+  </ItemGroup>
+
+</Project>

src/EchoHub.Tests/FileValidationHelperTests.cs

@@ -0,0 +1,56 @@
+using EchoHub.Server.Services;
+using Xunit;
+
+namespace EchoHub.Tests;
+
+public class FileValidationHelperTests
+{
+    [Fact]
+    public void IsValidImage_JpegMagicBytes_ReturnsTrue()
+    {
+        byte[] jpeg = [0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10];
+        using var stream = new MemoryStream(jpeg);
+        Assert.True(FileValidationHelper.IsValidImage(stream));
+    }
+
+    [Fact]
+    public void IsValidImage_PngMagicBytes_ReturnsTrue()
+    {
+        byte[] png = [0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A];
+        using var stream = new MemoryStream(png);
+        Assert.True(FileValidationHelper.IsValidImage(stream));
+    }
+
+    [Fact]
+    public void IsValidImage_GifMagicBytes_ReturnsTrue()
+    {
+        byte[] gif = [0x47, 0x49, 0x46, 0x38, 0x39, 0x61];
+        using var stream = new MemoryStream(gif);
+        Assert.True(FileValidationHelper.IsValidImage(stream));
+    }
+
+    [Fact]
+    public void IsValidImage_WebpMagicBytes_ReturnsTrue()
+    {
+        byte[] webp = [0x52, 0x49, 0x46, 0x46, 0x00, 0x00, 0x00, 0x00, 0x57, 0x45, 0x42, 0x50];
+        using var stream = new MemoryStream(webp);
+        Assert.True(FileValidationHelper.IsValidImage(stream));
+    }
+
+    [Fact]
+    public void IsValidImage_RandomBytes_ReturnsFalse()
+    {
+        byte[] random = [0x00, 0x01, 0x02, 0x03, 0x04, 0x05];
+        using var stream = new MemoryStream(random);
+        Assert.False(FileValidationHelper.IsValidImage(stream));
+    }
+
+    [Fact]
+    public void IsValidImage_ResetsStreamPosition()
+    {
+        byte[] jpeg = [0xFF, 0xD8, 0xFF, 0xE0, 0x00, 0x10];
+        using var stream = new MemoryStream(jpeg);
+        FileValidationHelper.IsValidImage(stream);
+        Assert.Equal(0, stream.Position);
+    }
+}

src/EchoHub.Tests/PresenceTrackerTests.cs

@@ -0,0 +1,68 @@
+using EchoHub.Server.Services;
+using Xunit;
+
+namespace EchoHub.Tests;
+
+public class PresenceTrackerTests
+{
+    [Fact]
+    public void UserConnected_IsOnline_ReturnsTrue()
+    {
+        var tracker = new PresenceTracker();
+        tracker.UserConnected("conn1", Guid.NewGuid(), "alice");
+        Assert.True(tracker.IsOnline("alice"));
+    }
+
+    [Fact]
+    public void UserDisconnected_LastConnection_IsOnlineReturnsFalse()
+    {
+        var tracker = new PresenceTracker();
+        tracker.UserConnected("conn1", Guid.NewGuid(), "alice");
+        tracker.UserDisconnected("conn1");
+        Assert.False(tracker.IsOnline("alice"));
+    }
+
+    [Fact]
+    public void MultipleConnections_DisconnectOne_StillOnline()
+    {
+        var tracker = new PresenceTracker();
+        var userId = Guid.NewGuid();
+        tracker.UserConnected("conn1", userId, "alice");
+        tracker.UserConnected("conn2", userId, "alice");
+        tracker.UserDisconnected("conn1");
+        Assert.True(tracker.IsOnline("alice"));
+    }
+
+    [Fact]
+    public void JoinChannel_GetOnlineUsersInChannel_ReturnsUser()
+    {
+        var tracker = new PresenceTracker();
+        tracker.UserConnected("conn1", Guid.NewGuid(), "alice");
+        tracker.JoinChannel("alice", "general");
+        var users = tracker.GetOnlineUsersInChannel("general");
+        Assert.Contains("alice", users);
+    }
+
+    [Fact]
+    public void LeaveChannel_UserNoLongerInChannel()
+    {
+        var tracker = new PresenceTracker();
+        tracker.UserConnected("conn1", Guid.NewGuid(), "alice");
+        tracker.JoinChannel("alice", "general");
+        tracker.LeaveChannel("alice", "general");
+        var users = tracker.GetOnlineUsersInChannel("general");
+        Assert.DoesNotContain("alice", users);
+    }
+
+    [Fact]
+    public void GetChannelsForUser_ReturnsJoinedChannels()
+    {
+        var tracker = new PresenceTracker();
+        tracker.UserConnected("conn1", Guid.NewGuid(), "alice");
+        tracker.JoinChannel("alice", "general");
+        tracker.JoinChannel("alice", "random");
+        var channels = tracker.GetChannelsForUser("alice");
+        Assert.Contains("general", channels);
+        Assert.Contains("random", channels);
+    }
+}

src/EchoHub.Tests/ValidationConstantsTests.cs

@@ -0,0 +1,46 @@
+using EchoHub.Core.Constants;
+using Xunit;
+
+namespace EchoHub.Tests;
+
+public class ValidationConstantsTests
+{
+    [Theory]
+    [InlineData("alice", true)]
+    [InlineData("Bob_123", true)]
+    [InlineData("user-name", true)]
+    [InlineData("abc", true)]
+    [InlineData("ab", false)]
+    [InlineData("", false)]
+    [InlineData("has space", false)]
+    [InlineData("has@symbol", false)]
+    public void UsernameRegex_ValidatesCorrectly(string input, bool expected)
+    {
+        var result = ValidationConstants.UsernameRegex().IsMatch(input);
+        Assert.Equal(expected, result);
+    }
+
+    [Theory]
+    [InlineData("general", true)]
+    [InlineData("my-channel_01", true)]
+    [InlineData("ab", true)]
+    [InlineData("a", false)]
+    [InlineData("has space", false)]
+    public void ChannelNameRegex_ValidatesCorrectly(string input, bool expected)
+    {
+        var result = ValidationConstants.ChannelNameRegex().IsMatch(input);
+        Assert.Equal(expected, result);
+    }
+
+    [Theory]
+    [InlineData("#FF0000", true)]
+    [InlineData("#aabbcc", true)]
+    [InlineData("FF0000", false)]
+    [InlineData("#FFF", false)]
+    [InlineData("#GGGGGG", false)]
+    public void HexColorRegex_ValidatesCorrectly(string input, bool expected)
+    {
+        var result = ValidationConstants.HexColorRegex().IsMatch(input);
+        Assert.Equal(expected, result);
+    }
+}

src/EchoHub.slnx

@@ -2,4 +2,5 @@
   <Project Path="EchoHub.Client/EchoHub.Client.csproj" />
   <Project Path="EchoHub.Core/EchoHub.Core.csproj" />
   <Project Path="EchoHub.Server/EchoHub.Server.csproj" />
+  <Project Path="EchoHub.Tests/EchoHub.Tests.csproj" />
 </Solution>