Breaking Down Task Comments

From Plan to Action

In previous lessons, we learned how to create a high-level technical plan . Now we're ready to move from planning to building. Our goal is to add a "Comments" feature to a task management system. Important Note About Practice Environment: The practices in this unit use a simplified implementation to focus on the decomposition methodology rather than production deployment. You'll work with: Basic Python classes instead of full FastAPI routers SQLite with integer IDs instead of Postgres with UUIDs Mocked external services instead of real cloud storage The skills you're learning (breaking down features, identifying dependencies, managing task scope) apply regardless of the specific tech stack. In professional work, you'd adapt these same principles to your production environment. In the CodeSignal IDE, basic libraries like SQLAlchemy and Pytest are installed, allowing you to focus on the logic of feature decomposition.

Decomposing the "Comments" Feature

To build a feature successfully, we group our work into logical phases. We call these "atomic tasks." A task is atomic if it focuses on one thing, affects only a few files, and can be finished in one sitting (usually under 2 hours). For our Comments feature, we split the work like this: Phase Task ID Focus Dependencies Foundation T001, T002 Database Model and Repository None Business Logic T003, T004 Services and Validation Schemas T001, T002 API Layer T005, T006 Endpoints and Authorization T003, T004 Integration T007 Final End-to-End Tests All previous By following this order, we ensure that we never build a "roof" (the API) before we have a "foundation" (the database).

Phase	Task ID	Focus	Dependencies
Foundation	`T001`, `T002`	Database Model and Repository	None
Business Logic	`T003`, `T004`	Services and Validation Schemas	`T001`, `T002`
API Layer	`T005`, `T006`	Endpoints and Authorization	`T003`, `T004`
Integration	`T007`	Final End-to-End Tests	All previous

Defining Task Requirements (The Template)

Every task needs a clear set of instructions so Claude knows exactly what "done" looks like. We use a standard template for this. Let's look at the requirements for our first task, T001 . Task Template: [T001] Create Comment Model Files Modified : src/models/comment.py, tests/unit/test_comment_model.py Acceptance Criteria : Model extends Base from src.database . Fields: id (Integer, primary key), task_id (Integer, Foreign Key), user_id (Integer, Foreign Key), content (String), created_at (DateTime with default). Relationships: task (to Task model), author (to User model). All foreign keys explicitly marked nullable=False . Unit tests verify fields, relationships, and default timestamp behavior. Dependencies : None Estimated Time : 45 minutes Notice the checkboxes. These are called Acceptance Criteria . They act as a checklist for both you and Claude . If every box isn't checked, the task isn't finished.

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The Test-First Workflow with Claude Code

When you start a task with Claude Code, you should use a "Test-First" workflow. This means we ask Claude to write the test before the actual code. This ensures the code is actually doing what we want.

Let's walk through how you would prompt Claude for T001.

Step 1: The Initial Prompt You tell Claude: "Create the Comment model following the T001 acceptance criteria. Write the tests first, verify they fail, then implement the model, and verify they pass."

Step 2: Writing the Failing Test Claude will first create a test file. Since the Comment model doesn't exist yet, the test will fail.

Python

# tests/unit/test_comment_model.py
import pytest
from src.models.comment import Comment

def test_new_comment_fields(db):
    # This will fail because src.models.comment does not exist yet
    comment = Comment(
        content="Great task!", 
        task_id=1, 
        user_id=1
    )
    db.add(comment)
    db.commit()
    
    assert comment.id is not None
    assert comment.content == "Great task!"
    assert comment.task_id == 1
    assert comment.user_id == 1

# tests/unit/test_comment_model.py
import pytest
from src.models.comment import Comment

def test_new_comment_fields(db):
    # This will fail because src.models.comment does not exist yet
    comment = Comment(
        content="Great task!", 
        task_id=1, 
        user_id=1
    )
    db.add(comment)
    db.commit()
    
    assert comment.id is not None
    assert comment.content == "Great task!"
    assert comment.task_id == 1
    assert comment.user_id == 1

When Claude runs this test, the output will look like this:

text

E   ModuleNotFoundError: No module named 'src.models.comment'

E   ModuleNotFoundError: No module named 'src.models.comment'

Step 3: Implementing the Model Now Claude writes the actual code to make the test pass, following the simplified patterns for the learning environment.

Python

# src/models/comment.py
from sqlalchemy import Column, Integer, String, ForeignKey, DateTime
from sqlalchemy.orm import relationship
from datetime import datetime
from src.database import Base


class Comment(Base):
    __tablename__ = "comments"
    
    id = Column(Integer, primary_key=True)
    task_id = Column(Integer, ForeignKey("tasks.id"), nullable=False)
    user_id = Column(Integer, ForeignKey("users.id"), nullable=False)
    content = Column(String, nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)

    # Relationships
    task = relationship("Task", back_populates="comments")
    author = relationship("User")

# src/models/comment.py
from sqlalchemy import Column, Integer, String, ForeignKey, DateTime
from sqlalchemy.orm import relationship
from datetime import datetime
from src.database import Base


class Comment(Base):
    __tablename__ = "comments"
    
    id = Column(Integer, primary_key=True)
    task_id = Column(Integer, ForeignKey("tasks.id"), nullable=False)
    user_id = Column(Integer, ForeignKey("users.id"), nullable=False)
    content = Column(String, nullable=False)
    created_at = Column(DateTime, default=datetime.utcnow)

    # Relationships
    task = relationship("Task", back_populates="comments")
    author = relationship("User")

Key Pattern Details:

We use Integer as the primary key type (simplified for learning environment)
We use Integer for foreign keys to match the simplified database
We use String for content (SQLite doesn't require length specifications)
The field is named user_id for the author of the comment
We use DateTime with default=datetime.utcnow for automatic timestamps
Relationships use back_populates to create bidirectional links

Step 4: Verifying Success Claude runs the test again. This time, it passes!

text

tests/unit/test_comment_model.py .                          [100%]
1 passed in 0.05s

tests/unit/test_comment_model.py .                          [100%]
1 passed in 0.05s

Finally, you would commit this work with a clear message: feat(comments): Add Comment model (T001).

From Plan to Action

Decomposing the "Comments" Feature

Defining Task Requirements (The Template)

Join the 1M+ learners on CodeSignal

The Test-First Workflow with Claude Code

Recognizing and Recovering from Task Bloat

Summary and Practice Prep