SMock Tests

SMock Tests

Discover the test structure, find gaps and non-SMock mocking patterns, and write or update .NET tests using the SMock library — proactively and without asking the user for guidance on which classes to test.

Arguments

An optional argument selects the default API style for generated tests:

• sequential — use using var mock = Mock.Setup(...).Returns(value) (default)
• hierarchical — use Mock.Setup(..., () => { /* validation */ }).Returns(value)

Core Operating Principle

Never ask the user which classes or methods to test. Discover all of it automatically:

1. Scan source projects for public classes and methods
2. Cross-reference against existing test files to find gaps
3. Check existing tests for non-SMock mocking (manual fakes, wrapper classes, Moq, etc.)
4. Write or update tests accordingly — only where mocking is warranted (see decision framework below)

Proceed with all discovered work unless the user has explicitly scoped the request.

When to Use SMock (Decision Framework)

Before writing any test, evaluate whether the method under test actually requires mocking. Adding unnecessary mocks makes tests brittle and harder to read.

Mock with SMock when the code calls:

Category	Examples
Non-deterministic BCL statics	DateTime.Now, DateTime.UtcNow, Guid.NewGuid(), Random.Next()
File system	File.Exists(), File.ReadAllText(), Directory.GetFiles(), Path.*
Environment / process	Environment.GetEnvironmentVariable(), Environment.MachineName, Environment.Exit()
Network / I/O	HttpClient static methods, WebRequest, Dns.GetHostName()
External services	Any static façade over a database, cache, message bus, or third-party API
System clock / timer	Stopwatch.GetTimestamp(), TimeProvider static members
Volatile or side-effecting statics	Logging singletons called via static, global config readers

Do NOT mock with SMock when:

• The method under test is a pure function — given the same input it always returns the same output with no side effects
• The dependency is an interface or abstract class — use constructor injection and pass a test double directly
• The logic is a simple data transformation (parsing, mapping, arithmetic, string manipulation)
• The call is to another internal/domain class you own and that class has no external dependencies
• No isolation is actually needed — the real implementation is cheap, fast, and deterministic in tests

How to apply during source scanning (Step 0)

For each public method found, check: does the method body (or any method it transitively calls) reach a static that is non-deterministic, has I/O side effects, or depends on external state? If yes → SMock candidate. If no → write a plain test without mocking.

Step 0: Discover Source Code

Before touching tests, map the source:

# Find all source .csproj files (exclude test projects)
find . -name "*.csproj" | grep -iv "\.tests" | head -20

# List public classes in source projects
grep -rl "public class\|public static class\|public interface" src/ \
  --include="*.cs" | grep -iv "test" | head -40

# Find methods that call static classes (likely need mocking)
grep -rn "static\|DateTime\.\|File\.\|Path\.\|Environment\." src/ \
  --include="*.cs" | grep -iv "test" | head -30

Read each discovered source file to understand:

• Public classes and their dependencies
• Static method calls that will need mocking
• Async vs sync methods

Step 0.5: Check and Update SMock Version

After locating test .csproj files, verify all SMock references use the latest published version.

# Fetch the latest stable SMock version from NuGet
LATEST=$(curl -s "https://api.nuget.org/v3-flatcontainer/smock/index.json" \
  | grep -oE '"[0-9]+\.[0-9]+\.[0-9]+"' | tr -d '"' | sort -V | tail -1)
echo "Latest SMock on NuGet: $LATEST"

# Find all .csproj files referencing SMock
grep -rl 'Include="SMock"' . --include="*.csproj"

For each .csproj found, read the current Version attribute on the SMock PackageReference:

grep 'SMock' path/to/Project.Tests.csproj

If the version is outdated (pinned to an older release, not *, or * is resolving to an old locked version):

1. Edit the .csproj — update the Version attribute to the fetched $LATEST value
2. Run dotnet restore in the src/ directory to pull the updated package
3. Confirm the restore succeeded before continuing

If Version="*" is already present: run dotnet restore once to ensure the wildcard resolves to the latest, then confirm via:

dotnet list path/to/Project.Tests.csproj package | grep SMock

Skip this step only when no test .csproj files exist yet (they will be created in Step 2 using the latest version).

Step 1: Discover and Audit Test Structure

# Find existing test projects
find . -name "*.csproj" | grep -i "\.tests" | head -20
ls src/ 2>/dev/null | grep -i test

If a test project exists:

• Read its .csproj for TargetFramework and package references
• Find existing test class files matching the source classes
• Audit for non-SMock patterns:

# Find tests NOT using SMock
grep -rl "using StaticMock" src/ --include="*.cs" | sort > /tmp/smock_files.txt
find src/ -name "*Tests*.cs" | sort > /tmp/all_test_files.txt
comm -23 /tmp/all_test_files.txt /tmp/smock_files.txt  # tests missing SMock

# Find competing mock patterns to replace
grep -rn "new Mock<\|\.Setup(\|Moq\.\|FakeItEasy\.\|wrapper\|wrapper class" \
  src/ --include="*.cs" | grep -i test

If non-SMock patterns are found: proceed to Step 2 / Step 3 to fix them.

If every test file already uses SMock (the comm output is empty and no competing patterns found): proceed directly to Step 1.5 for a full correctness and coverage audit.

If no test project exists: proceed to Step 2.

Step 1.5: Correctness and Coverage Audit

Run this step whenever the codebase is already on SMock and the skill is invoked without a specific fix request. The goal is to surface real problems — incorrect usage and uncovered scenarios — not cosmetic issues.

Correctness: scan for SMock anti-patterns

# Sequential mocks missing 'using var' (leaves hook active, corrupts other tests)
grep -rn "var [a-zA-Z_]* = Mock\.Setup" src/ --include="*.cs" | grep -v "using var"

# Standalone 'It' not accessed through context lambda
grep -rn "\bIt\.IsAny\|\bIt\.Is(" src/ --include="*.cs"

# Callback called on IFuncMock (only valid on IActionMock)
grep -rn "\.Returns(.*)\s*\n?\s*\.Callback\|\.Returns(.*).Callback" src/ --include="*.cs"

# Missing <Optimize>false</Optimize> in test .csproj files
grep -rL "Optimize>false" . --include="*.csproj" | grep -i test

For each hit, read the surrounding context and determine if it is a genuine violation. Report findings grouped by file, with line numbers.

Coverage: find mocking gaps

For each source method identified as an SMock candidate in Step 0 (non-deterministic / I/O / external):

1. Check whether a corresponding test method exists in the test project
2. Check whether that test method actually contains a Mock.Setup call targeting the external dependency

# List all public methods in source that touch non-deterministic statics
grep -rn "DateTime\.\|File\.\|Environment\.\|Guid\.NewGuid\|Random\." src/ \
  --include="*.cs" | grep -iv test

# For each source class, check if a *Tests class exists
# e.g. for FileService.cs → grep for FileServiceTests in test files

For each gap found (mock candidate with no test or no Mock.Setup):

• Note the source method and what it calls that needs mocking
• Note whether no test exists at all, or a test exists but doesn't mock the dependency

Audit Report Format

After completing the audit, produce a concise report before making any changes:

## SMock Audit Report

### Correctness Issues
- [FILE:LINE] Missing `using var` on Sequential mock
- [FILE:LINE] Standalone `It.IsAny<T>()` — should be `context.It.IsAny<T>()`
- [FILE] Missing <Optimize>false</Optimize> in .csproj

### Coverage Gaps
- [SourceClass.Method] calls DateTime.Now — no test mocking this dependency
- [SourceClass.OtherMethod] calls File.ReadAllText — test exists but does not mock File access

### All Clear
- (listed items that were checked and passed)

Then fix all issues found using Step 3. If nothing is found, report "All clear — SMock usage is correct and coverage is complete."

Step 2: Create Test Project (if needed)

Naming conventions (non-negotiable):

Item	Convention	Example
Test project	OriginalProject.Tests	MyService.Tests
Test class	OriginalClassNameTests	FileServiceTests
Test method	Test + MethodName + Description	TestGetUserReturnsActiveUser

1. Create src/OriginalProject.Tests/ directory
2. Create the .csproj file (see references/test-structure.md for full template — includes <Optimize>false</Optimize>, SMock package ref, NUnit)
3. Add to the solution: dotnet sln add src/OriginalProject.Tests/OriginalProject.Tests.csproj
4. Mirror source folder structure in the test project

Step 3: Write or Update Tests with SMock

Always add using StaticMock; and using NUnit.Framework.Legacy; at the top of each test file.

For every public class or method discovered in Step 0 that lacks adequate SMock coverage: write tests. Don't skip a class because it wasn't mentioned by the user.

For existing tests using non-SMock patterns: replace them with the SMock equivalents below.

Sequential API (default)

[Test]
public void TestMethodNameDoesExpectedBehavior()
{
    using var mock = Mock.Setup(() => TargetClass.StaticMethod())
        .Returns(expectedValue);

    var result = systemUnderTest.MethodThatCallsStatic();

    ClassicAssert.AreEqual(expectedValue, result);
}

With parameter matching:

using var mock = Mock.Setup(context => TargetClass.Method(context.It.IsAny<string>()))
    .Returns(expectedValue);

Hierarchical API

[Test]
public void TestMethodNameWithInlineValidation()
{
    Mock.Setup(context => TargetClass.Method(context.It.IsAny<string>()), () =>
    {
        var result = TargetClass.Method("input");
        ClassicAssert.IsNotNull(result);
        ClassicAssert.AreEqual(expectedValue, result);
    }).Returns(expectedValue);
}

Core SMock Rules

1. Sequential mocks must use using var — omitting it leaves the hook active and corrupts other tests
2. Access It only through the lambda's context parameter: context.It.IsAny<T>() — never standalone It
3. Async methods: .ReturnsAsync(value) (preferred) or .Returns(Task.FromResult(value))
4. Void methods (IActionMock): .Callback<T>(p => { }) — only IActionMock has Callback, not IFuncMock
5. Exceptions (no-arg): .Throws<ExceptionType>() — requires ExceptionType to have a parameterless constructor
6. Exceptions (with args): .Throws<ExceptionType>(new object[] { "message", arg2 }) or .Throws(typeof(ExceptionType), "message")
7. Instance methods and static properties use the same lambda syntax as static methods
8. Add [MethodImpl(MethodImplOptions.NoOptimization)] to a test method if mocks don't intercept in Release builds

Step 4: Update Project CLAUDE.md

After writing tests, update (or create) the CLAUDE.md at the project root:

1. Check if a CLAUDE.md exists at the root of the project being tested
2. If it exists, find the testing section and add or update an SMock usage note
3. If it doesn't exist, create one with at minimum:
   • The test project name and location
   • That SMock is used for mocking (NuGet package name: SMock)
   • Which API style is the default (Sequential or Hierarchical)
   • Naming conventions (project / class / method)

## Testing

Tests live in `src/OriginalProject.Tests/`. Use the SMock library (`using StaticMock;`) for all mocking.

- **Default style**: Sequential (`using var mock = Mock.Setup(...).Returns(value)`)
- **Test class naming**: `OriginalClassNameTests`
- **Test method naming**: `Test` + MethodName [+ Description]

Step 5: Validate Compilation and Tests Pass

cd src

# Build in Debug (required — optimizer can break SMock hooks)
dotnet build --configuration Debug

# Run the tests for the affected project
dotnet test --configuration Debug --framework net8.0 --verbosity minimal \
  --filter "FullyQualifiedName~OriginalProject.Tests"

If the build fails:

• Check for missing using statements (using StaticMock;, using NUnit.Framework;, etc.)
• Verify the .csproj references both the SMock package and the source project
• Ensure <Optimize>false</Optimize> is present in the test .csproj

If tests fail:

• Check that using var is used for all Sequential mocks
• Verify .Throws<T>() has the parameterless constructor constraint satisfied
• Confirm context.It.IsAny<T>() is used — not a standalone It reference

Additional Resources

Consult these references for detailed information:

• references/api-reference.md — All Mock.Setup overloads, IFuncMock, IActionMock, IAsyncFuncMock, SetupProperty, SetupAction, SetupDefault, complete Throws and Callback signatures
• references/test-structure.md — Full .csproj template, solution integration, namespace conventions, NUnit attributes, test organization
• references/patterns.md — Common patterns: time-dependent testing, file system mocking, async mocking, callbacks, conditional returns, exception testing, multiple coordinated mocks