detect-static-dependencies

name	detect-static-dependencies
description	Scan C# source files for hard-to-test static dependencies — DateTime.Now/UtcNow, File.*, Directory.*, Environment.*, HttpClient, Console.*, Process.*, and other untestable statics. Produces a ranked report of static call sites by frequency. USE FOR: find untestable statics, scan for static dependencies, testability audit, identify hard-to-mock code, find DateTime.Now usage, detect static coupling, testability report, static analysis for testability. DO NOT USE FOR: generating wrappers (use generate-testability-wrappers), migrating code (use migrate-static-to-wrapper), general code review, or finding statics that are already behind abstractions.
license	MIT

Detect Static Dependencies

Scan a C# codebase for calls to hard-to-test static APIs and produce a ranked report showing which statics appear most frequently, which files are most affected, and which abstractions already exist in the .NET ecosystem to replace them.

When to Use

• Auditing a project's testability before adding unit tests
• Understanding the scope of static coupling in a legacy codebase
• Prioritizing which statics to wrap first (highest-frequency wins)
• Creating a migration plan for incremental testability improvements

Response Guidelines

• Scale the response to the user's request. A question about a specific category (e.g., "find time statics") should focus on that category with file locations and counts, not produce a full report across all categories.
• When the user provides a specific file or directory path, scan only that scope — do not expand to the entire solution unless asked.
• The full structured report format in Step 4 is for comprehensive audit requests. For focused questions, return only the relevant subset (e.g., category summary + affected files for the requested category).

When Not to Use

• The user wants wrappers generated (hand off to generate-testability-wrappers)
• The user wants mechanical migration done (hand off to migrate-static-to-wrapper)
• The statics are already behind interfaces or TimeProvider
• The code is not C# / .NET

Inputs

Input	Required	Description
Target path	Yes	A file, directory, project (.csproj), or solution (.sln) to scan
Exclusion patterns	No	Glob patterns to skip (e.g., **/obj/**, **/Migrations/**)
Category filter	No	Limit to specific categories: time, filesystem, environment, network, console, process

Workflow

Step 1: Determine scan scope

Resolve the target to a set of .cs files:

• If a .cs file, scan that single file.
• If a directory, scan all .cs files recursively (excluding obj/, bin/).
• If a .csproj, find its directory and scan .cs files within.
• If a .sln, parse it, find all project directories, and scan .cs files across all projects.

Always exclude obj/, bin/, and any user-specified exclusion patterns.

Step 2: Search for static dependency patterns

Scan each file for calls matching these categories:

Category	Patterns to search for	Recommended replacement
Time	DateTime.Now, DateTime.UtcNow, DateTime.Today, DateTimeOffset.Now, DateTimeOffset.UtcNow, Task.Delay(, new CancellationTokenSource(TimeSpan	TimeProvider (.NET 8+)
File System	File.ReadAllText(, File.WriteAllText(, File.Exists(, File.Delete(, File.Copy(, File.Move(, Directory.Exists(, Directory.CreateDirectory(, Directory.GetFiles(, Directory.Delete(, Path.Combine(, Path.GetTempPath(	IFileSystem (System.IO.Abstractions NuGet)
Environment	Environment.GetEnvironmentVariable(, Environment.SetEnvironmentVariable(, Environment.MachineName, Environment.UserName, Environment.CurrentDirectory, Environment.Exit(	Custom IEnvironmentProvider
Network	new HttpClient(, HttpClient.GetAsync(, HttpClient.PostAsync(, HttpClient.SendAsync(	IHttpClientFactory (built-in)
Console	Console.WriteLine(, Console.ReadLine(, Console.Write(, Console.ReadKey(	IConsole wrapper or ILogger
Process	Process.Start(, Process.GetCurrentProcess(, Process.GetProcessesByName(	Custom IProcessRunner

Step 3: Aggregate and rank results

Count each static call pattern across the entire scan scope. Produce a summary with:

1. Category summary — total call sites per category (time, filesystem, env, etc.)
2. Top patterns — the 10 most frequent individual patterns ranked by count
3. Most affected files — files with the highest number of static dependencies
4. Existing abstractions available — for each category, note the recommended .NET abstraction:
   • Time → TimeProvider (built-in since .NET 8)
   • File system → System.IO.Abstractions (NuGet package)
   • HTTP → IHttpClientFactory (built-in)
   • Environment → custom IEnvironmentProvider
   • Console → custom IConsole or ILogger
   • Process → custom IProcessRunner

Step 4: Present the report

Format the output as a structured report:

## Static Dependency Report

**Scope**: <project/solution name>
**Files scanned**: <count>
**Total static call sites**: <count>

### Category Summary
| Category     | Call Sites | Recommended Abstraction |
|-------------|-----------|------------------------|
| Time         | 42        | TimeProvider (.NET 8+) |
| File System  | 31        | System.IO.Abstractions |
| Environment  | 12        | IEnvironmentProvider   |
| ...          | ...       | ...                    |

### Top 10 Patterns
| # | Pattern             | Count | Files |
|---|---------------------|-------|-------|
| 1 | DateTime.UtcNow     | 28    | 14    |
| 2 | File.ReadAllText    | 18    | 9     |
| ...                                      |

### Most Affected Files
| File                          | Static Calls | Categories          |
|-------------------------------|-------------|---------------------|
| Services/OrderProcessor.cs    | 12          | Time, FileSystem    |
| ...                                                               |

### Migration Priority
1. **Time** (42 sites) — Use `TimeProvider`, zero NuGet dependencies on .NET 8+
2. **File System** (31 sites) — Use `System.IO.Abstractions` NuGet package
3. ...

Step 5: Suggest next steps

Based on the report, recommend:

• Which category to tackle first (fewest dependencies, best built-in support)
• Whether to use generate-testability-wrappers for custom wrapper generation
• Whether to use migrate-static-to-wrapper for mechanical bulk migration

Validation

• All .cs files in scope were scanned (check count)
• Report includes category totals, top patterns, and affected files
• Each detected pattern has a recommended replacement listed
• obj/ and bin/ directories were excluded
• Migration priority is ordered by impact (count × ease of replacement)

Common Pitfalls

Pitfall	Solution
Scanning obj/ or generated code	Always exclude obj/, bin/, and *.Designer.cs
Counting wrapped calls as statics	Check if the call is behind an interface or injected service before counting
Missing statics inside lambdas/LINQ	Search covers all code within .cs files, including lambdas
Recommending TimeProvider on < .NET 8	Check TargetFramework in .csproj — if < net8.0, recommend NodaTime.IClock or custom ISystemClock
Ignoring test projects	Only scan production code — exclude *.Tests.csproj projects from the scan