Detect Static Dependencies

Step 3: Aggregate and rank results

Count each call site across the entire scan scope — including the instance-member call sites covered by the rules below, not only static ones.

Counting rules — inaccurate totals are the main way this report loses to an ad-hoc scan:

• Build one occurrence ledger before writing prose. Give each included call site exactly one row containing category, exact pattern, file:line, and recommended seam. Derive every category, pattern, and per-file count by grouping that same ledger; never recount independently while writing tables.
• Keep the three count domains separate. Files scanned includes every eligible source file; affected files includes only files with ledger rows; call sites is the number of ledger rows. Never substitute one for another.
• One authoritative total. Every call site you found belongs in the category summary and the grand total. Never park real findings in an "additional observations" section that the totals exclude.
• Classify by what the member touches, not by whether it is static. Instance members that reach the same untestable resource still count and belong in the matching category (new FileInfo(path).LastWriteTimeUtc → File System; new HttpClient().GetAsync(...) → Network). Say "hidden dependency", not "static", when the member is an instance call.
• Check receiver provenance before counting instance calls. Count a resource access only when the code under test acquires or constructs the dependency itself. Exclude constructor-, parameter-, property-, and DI-injected collaborators from the "needs wrapping" total, including concrete HttpClient instances.
• Exclude deterministic pure helpers from the "needs wrapping" total. Path.Combine, Path.GetExtension, Path.GetFileName, and Math.*/string.* statics take no ambient input and are trivially testable. List them, if at all, in a separate "no action needed" note — never as testability blockers.
• Cover every category before reporting — time, file system, environment, network, console, process, randomness (new Random(), Guid.NewGuid()), culture (CultureInfo.CurrentCulture), and serialization/statics such as JsonSerializer. Omitting a category that is present is an under-count.
• Give file:line for every occurrence so the user can jump straight to it.
• Reconcile before publishing. The category totals, the top-patterns table, and the per-file table must sum to the same grand total.
• Treat exclusions as a scope decision, not a category. Remove obj/, bin/, generated, and user-excluded files before building the ledger. Do not include their files or call sites in any reported count. State the exclusions once rather than mixing excluded candidates into the arithmetic.
• Label truncated rankings. In a comprehensive audit, list all distinct patterns when needed for reconciliation. If the user asked only for a top-N subset, label it as a subset and do not imply that its rows sum to the grand total.

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 (highest count, best built-in support). Keep this to a few lines.

Mention generate-testability-wrappers or migrate-static-to-wrapper only when the user's next action clearly needs them — a hand-off note, not a sales pitch. Never end an audit with promotional next-steps that dilute the findings.

Validation

• All .cs files in scope were scanned (check count)
• Report includes category totals, top patterns, and affected files
• Category totals, top patterns, and per-file counts reconcile to the same grand total
• Files scanned, affected files, and call sites are reported as different quantities
• Every aggregate was derived from one occurrence ledger rather than independently recounted
• Every occurrence carries a file:line location
• No findings are held outside the totals in an "additional" section
• Calls on injected collaborators are excluded from the "needs wrapping" total
• Deterministic pure helpers (Path.Combine, Math.*) are not counted as testability blockers
• 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