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

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:

Category summary — total call sites per category (time, filesystem, env, etc.)
Top patterns — the 10 most frequent individual patterns ranked by count
Most affected files — files with the highest number of static dependencies
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

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