---
test_id: diagrams-architect-002
test_name: Sequence Diagram Generation
coverage:
  - TC-B008 # Skill detects sequence diagram request
  - TC-B009 # Agent generates sequenceDiagram syntax
  - TC-B010 # Participants clearly labeled
  - TC-B011 # Flow accurately represents process
  - TC-B012 # Saved to correct location
  - TC-B013 # File named correctly
priority: P1
tags:
  - sequence-diagram
  - interaction-flow
  - authentication
---

# Test Case: Sequence Diagram Generation

## Scenario

User requests a sequence diagram to understand the login authentication flow, including success and failure paths.

## Input

**User Request**: "Create sequence diagram for login flow"

**Context Provided** (optional):
- User submits credentials via browser
- AuthService validates against database
- Session created on success
- Error message on failure

## Expected Agent Behavior

1. **Recognize diagram type**: Sequence diagram
2. **Choose appropriate template**: `sequence-template.mmd`
3. **Generate diagram** with:
   - Participants: User, Browser, AuthService, Database, SessionStore
   - Clear interaction sequence
   - Success path (alt) and failure path (else)
   - Activation boxes showing processing time
   - Response arrows (dashed)
4. **Validate syntax**:
   - Starts with `sequenceDiagram` (uses `mermaid` keyword for non-C4)
   - All participants defined
   - Message arrows correct (->>, -->>)
   - Alt/else blocks properly structured
5. **Specify file path**: `.specweave/docs/internal/architecture/diagrams/auth/flows/login-flow.mmd`
6. **Provide validation instructions**

## Expected Output

**Diagram Content** (approximate):
```
sequenceDiagram
    participant User
    participant Browser
    participant AuthService
    participant Database
    participant SessionStore

    User->>Browser: Enter credentials
    Browser->>AuthService: POST /api/auth/login
    activate AuthService

    AuthService->>Database: Query user by email
    Database-->>AuthService: User record

    AuthService->>AuthService: Verify password (bcrypt)

    alt Password valid
        AuthService->>SessionStore: Create session
        SessionStore-->>AuthService: Session ID
        AuthService-->>Browser: 200 OK + Session cookie
        Browser-->>User: Redirect to dashboard
    else Password invalid
        AuthService-->>Browser: 401 Unauthorized
        Browser-->>User: Show error message
    end

    deactivate AuthService
```

**File Path**: `.specweave/docs/internal/architecture/diagrams/auth/flows/login-flow.mmd`

**Validation Message**:
```
✅ Diagram created: .specweave/docs/internal/architecture/diagrams/auth/flows/login-flow.mmd

📋 VALIDATION REQUIRED:
1. Open the file in VS Code
2. Verify the sequence diagram renders correctly
3. Confirm all participants and messages are clear
4. Verify success and failure paths are visible
```

## Success Criteria

- [ ] Diagram uses correct sequenceDiagram syntax
- [ ] Includes `mermaid` keyword (standard for non-C4 diagrams)
- [ ] All participants clearly defined
- [ ] Request arrows are solid (->>)
- [ ] Response arrows are dashed (-->>)
- [ ] Alt/else block shows conditional logic
- [ ] Activate/deactivate shows processing time
- [ ] File path follows conventions (module/flows/ subdirectory)
- [ ] Validation instructions provided
- [ ] Diagram would render correctly

## Failure Scenarios

**Scenario 1: Missing participant definition**
```
sequenceDiagram
    User->>Browser: Enter credentials
```
❌ FAIL: Participants should be explicitly defined

**Scenario 2: Wrong arrow types**
```
Browser-->>AuthService: POST /api/auth/login
```
❌ FAIL: Requests should use solid arrows (->>) not dashed

**Scenario 3: Missing alt/else for conditional flow**
```
AuthService->>SessionStore: Create session
AuthService-->>Browser: 401 Unauthorized
```
❌ FAIL: Should use alt/else to show conditional paths

**Scenario 4: Incorrect file location**
```
File: .specweave/docs/internal/architecture/diagrams/login-flow.mmd
```
❌ FAIL: Should be in module-specific `flows/` subdirectory

## Traceability

**Covers User Stories**:
- US-B002: Create Sequence Diagram

**Covers Acceptance Criteria**:
- TC-B008: Skill detects sequence diagram request
- TC-B009: Agent generates sequenceDiagram syntax
- TC-B010: Participants clearly labeled
- TC-B011: Flow accurately represents login process
- TC-B012: Diagram saved to correct location
- TC-B013: File named `login-flow.sequence.mmd` or `login-flow.mmd`