testing-anti-patterns

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# Testing Anti-Patterns

## Overview

Tests must verify real behavior, not mock behavior. Mocks are a means to isolate, not the thing being tested.

**Core principle:** Test what the code does, not what the mocks do.

**Following strict TDD prevents these anti-patterns.**

## The Iron Laws

```
1. NEVER test mock behavior
2. NEVER add test-only methods to production classes
3. NEVER mock without understanding dependencies
```

## Anti-Pattern 1: Testing Mock Behavior

**The violation:**
```csharp
// ❌ BAD: Testing that the mock exists
[Fact]
public void RenderPage_ShouldRenderSidebar()
{
    // Arrange
    var mockSidebar = new Mock<ISidebar>();
    var page = new Page(mockSidebar.Object);

    // Act
    var result = page.Render();

    // Assert
    mockSidebar.Verify(x => x.IsVisible, Times.Once); // Testing mock!
}
```

**Why this is wrong:**
- You're verifying the mock works, not that the component works
- Test passes when mock is present, fails when it's not
- Tells you nothing about real behavior

**your human partner's correction:** "Are we testing the behavior of a mock?"

**The fix:**
```csharp
// ✅ GOOD: Test real component or don't mock it
[Fact]
public void RenderPage_ShouldIncludeSidebarContent()
{
    // Arrange
    var sidebar = new Sidebar(); // Don't mock sidebar
    var page = new Page(sidebar);

    // Act
    var result = page.Render();

    // Assert
    Assert.Contains("navigation", result.Content);
}

// OR if sidebar must be mocked for isolation:
// Don't assert on the mock - test Page's behavior with sidebar present
```

### Gate Function

```
BEFORE asserting on any mock element:
  Ask: "Am I testing real component behavior or just mock existence?"

  IF testing mock existence:
    STOP - Delete the assertion or unmock the component

  Test real behavior instead
```

## Anti-Pattern 2: Test-Only Methods in Production

**The violation:**
```csharp
// ❌ BAD: Destroy() only used in tests
public class Session
{
    public async Task DestroyAsync()  // Looks like production API!
    {
        await _workspaceManager?.DestroyWorkspaceAsync(Id);
        // ... cleanup
    }
}

// In tests
public async Task TearDown() => await _session.DestroyAsync();
```

**Why this is wrong:**
- Production class polluted with test-only code
- Dangerous if accidentally called in production
- Violates YAGNI and separation of concerns
- Confuses object lifecycle with entity lifecycle

**The fix:**
```csharp
// ✅ GOOD: Test utilities handle test cleanup
// Session has no Destroy() - it's stateless in production

// In TestUtilities/
public static class SessionTestHelpers
{
    public static async Task CleanupSessionAsync(Session session)
    {
        var workspace = session.GetWorkspaceInfo();
        if (workspace != null)
        {
            await WorkspaceManager.DestroyWorkspaceAsync(workspace.Id);
        }
    }
}

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