diff --git a/.gitignore b/.gitignore
index ee64372..3a2962d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,87 @@
+# IDE
 .idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# Python
 *.pyc
+__pycache__/
+*.pyo
+*.pyd
+.Python
+*.so
+*.egg
+*.egg-info/
+dist/
+build/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# Virtual Environment
+venv/
+env/
+ENV/
+.venv/
+.ENV/
+
+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+coverage.xml
+*.cover
+.hypothesis/
+.tox/
+.nox/
+
+# Claude
+.claude/*
+
+# Database
+*.db
+*.sqlite
+*.sqlite3
+instance/
+
+# Flask
+instance/
+.webassets-cache
+
+# Logs
+*.log
+
+# OS
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db
+
+# Environment variables
+.env
+.env.local
+.env.*.local
+
+# Package managers
+# Note: Don't ignore poetry.lock or uv.lock
+node_modules/
+
+# Misc
+*.bak
+.cache/
diff --git a/pyproject.toml b/pyproject.toml
new file mode 100644
index 0000000..bb567f6
--- /dev/null
+++ b/pyproject.toml
@@ -0,0 +1,140 @@
+[tool.poetry]
+name = "flask-blog"
+version = "0.1.0"
+description = "A Flask-based blog application"
+authors = ["Your Name <you@example.com>"]
+readme = "README.md"
+packages = [{include = "app"}]
+
+[tool.poetry.dependencies]
+python = "^3.8.1"
+Flask = "0.10.1"
+Flask-Script = "2.0.5"
+Flask-SQLAlchemy = "2.1"
+Flask-Migrate = "1.7.0"
+Flask-WTF = "0.12"
+Flask-Bootstrap = "3.3.5.7"
+WTForms = "2.1"
+itsdangerous = "0.24"
+Jinja2 = "2.8"
+MarkupSafe = "0.23"
+SQLAlchemy = "1.0.11"
+Werkzeug = "0.11.3"
+wheel = "0.24.0"
+flask-login = "0.3.2"
+flask-moment = "0.5.1"
+ForgeryPy = "0.1"
+gunicorn = "19.4.5"
+psycopg2-binary = "2.9.9"
+
+[tool.poetry.group.dev.dependencies]
+pytest = "^6.2.0"
+pytest-cov = "^3.0.0"
+pytest-mock = "^3.6.0"
+pytest-flask = "^1.2.0"
+
+[tool.poetry.scripts]
+test = "pytest:main"
+tests = "pytest:main"
+
+[tool.pytest.ini_options]
+minversion = "7.0"
+testpaths = ["tests"]
+python_files = ["test_*.py", "*_test.py"]
+python_classes = ["Test*"]
+python_functions = ["test_*"]
+addopts = [
+    "-ra",
+    "--strict-markers",
+    "--cov=app",
+    "--cov-branch",
+    "--cov-report=term-missing",
+    "--cov-report=html:htmlcov",
+    "--cov-report=xml:coverage.xml",
+    "--cov-fail-under=80",
+    "-vv",
+    "--tb=short",
+    "--maxfail=1",
+]
+markers = [
+    "unit: Unit tests",
+    "integration: Integration tests",
+    "slow: Slow running tests",
+]
+filterwarnings = [
+    "ignore::DeprecationWarning",
+    "ignore::PendingDeprecationWarning",
+]
+
+[tool.coverage.run]
+source = ["app"]
+branch = true
+omit = [
+    "*/tests/*",
+    "*/migrations/*",
+    "*/__init__.py",
+    "*/config.py",
+    "*/manage.py",
+]
+
+[tool.coverage.report]
+precision = 2
+show_missing = true
+skip_covered = false
+skip_empty = true
+exclude_lines = [
+    "pragma: no cover",
+    "def __repr__",
+    "if self.debug:",
+    "if settings.DEBUG",
+    "raise AssertionError",
+    "raise NotImplementedError",
+    "if 0:",
+    "if __name__ == .__main__.:",
+    "if TYPE_CHECKING:",
+    "class .*\\bProtocol\\):",
+    "@(abc\\.)?abstractmethod",
+]
+
+[tool.coverage.html]
+directory = "htmlcov"
+
+[tool.coverage.xml]
+output = "coverage.xml"
+
+[tool.isort]
+profile = "black"
+line_length = 88
+known_first_party = ["app"]
+skip_glob = ["*/migrations/*"]
+
+[tool.black]
+line-length = 88
+target-version = ['py38']
+include = '\.pyi?$'
+exclude = '''
+/(
+    \.git
+  | \.hg
+  | \.mypy_cache
+  | \.tox
+  | \.venv
+  | _build
+  | buck-out
+  | build
+  | dist
+  | migrations
+)/
+'''
+
+[tool.mypy]
+python_version = "3.8"
+warn_return_any = true
+warn_unused_configs = true
+disallow_untyped_defs = false
+ignore_missing_imports = true
+exclude = ["migrations/", "tests/"]
+
+[build-system]
+requires = ["poetry-core"]
+build-backend = "poetry.core.masonry.api"
\ No newline at end of file
diff --git a/requirements/test.txt b/requirements/test.txt
new file mode 100644
index 0000000..0557ae2
--- /dev/null
+++ b/requirements/test.txt
@@ -0,0 +1,5 @@
+pytest==6.2.5
+pytest-cov==3.0.0
+pytest-mock==3.6.1
+pytest-flask==1.2.0
+coverage[toml]==6.5.0
\ No newline at end of file
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 0000000..157a8ca
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,25 @@
+import os
+import tempfile
+import pytest
+
+
+@pytest.fixture
+def temp_dir():
+    """Create a temporary directory."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        yield tmpdir
+
+
+@pytest.fixture
+def mock_config(monkeypatch):
+    """Mock configuration values."""
+    def _mock_config(key, value):
+        monkeypatch.setattr(f'config.Config.{key}', value)
+    return _mock_config
+
+
+@pytest.fixture(autouse=True)
+def reset_environment(monkeypatch):
+    """Reset environment variables for each test."""
+    monkeypatch.setenv('FLASK_CONFIG', 'testing')
+    monkeypatch.setenv('DATABASE_URL', 'sqlite:///:memory:')
\ No newline at end of file
diff --git a/tests/conftest_full.py b/tests/conftest_full.py
new file mode 100644
index 0000000..e56e6b6
--- /dev/null
+++ b/tests/conftest_full.py
@@ -0,0 +1,199 @@
+import os
+import tempfile
+import pytest
+from app import create_app, db
+from app.models import User, Role, Post, Comment
+from config import config
+
+
+@pytest.fixture(scope='session')
+def app():
+    """Create and configure a new app instance for each test session."""
+    app = create_app('testing')
+    app.config.update({
+        'TESTING': True,
+        'WTF_CSRF_ENABLED': False,
+        'SQLALCHEMY_DATABASE_URI': 'sqlite:///:memory:',
+        'SERVER_NAME': 'localhost:5000',
+    })
+    
+    with app.app_context():
+        yield app
+
+
+@pytest.fixture(scope='function')
+def _db(app):
+    """Create a new database for each test function."""
+    with app.app_context():
+        db.create_all()
+        yield db
+        db.session.remove()
+        db.drop_all()
+
+
+@pytest.fixture(scope='function')
+def session(_db):
+    """Creates a new database session for a test."""
+    connection = _db.engine.connect()
+    transaction = connection.begin()
+
+    options = dict(bind=connection, binds={})
+    session = _db.create_scoped_session(options=options)
+
+    _db.session = session
+
+    yield session
+
+    transaction.rollback()
+    connection.close()
+    session.remove()
+
+
+@pytest.fixture
+def client(app):
+    """A test client for the app."""
+    return app.test_client()
+
+
+@pytest.fixture
+def runner(app):
+    """A test runner for the app's Click commands."""
+    return app.test_cli_runner()
+
+
+@pytest.fixture
+def auth_client(client, user):
+    """A test client that is logged in."""
+    with client:
+        client.post('/auth/login', data={
+            'email': user.email,
+            'password': 'testpassword'
+        })
+    return client
+
+
+@pytest.fixture
+def temp_dir():
+    """Create a temporary directory."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        yield tmpdir
+
+
+@pytest.fixture
+def mock_config(monkeypatch):
+    """Mock configuration values."""
+    def _mock_config(key, value):
+        monkeypatch.setattr(f'config.Config.{key}', value)
+    return _mock_config
+
+
+@pytest.fixture
+def user(_db):
+    """Create a test user."""
+    user = User(
+        email='test@example.com',
+        username='testuser',
+        password='testpassword',
+        confirmed=True
+    )
+    _db.session.add(user)
+    _db.session.commit()
+    return user
+
+
+@pytest.fixture
+def admin_user(_db):
+    """Create a test admin user."""
+    admin_role = Role.query.filter_by(name='Administrator').first()
+    if not admin_role:
+        admin_role = Role(name='Administrator', permissions=0xff)
+        _db.session.add(admin_role)
+    
+    admin = User(
+        email='admin@example.com',
+        username='admin',
+        password='adminpassword',
+        role=admin_role,
+        confirmed=True
+    )
+    _db.session.add(admin)
+    _db.session.commit()
+    return admin
+
+
+@pytest.fixture
+def post(_db, user):
+    """Create a test post."""
+    post = Post(
+        title='Test Post',
+        body='This is a test post body.',
+        author=user
+    )
+    _db.session.add(post)
+    _db.session.commit()
+    return post
+
+
+@pytest.fixture
+def comment(_db, user, post):
+    """Create a test comment."""
+    comment = Comment(
+        body='This is a test comment.',
+        author=user,
+        post=post
+    )
+    _db.session.add(comment)
+    _db.session.commit()
+    return comment
+
+
+@pytest.fixture(autouse=True)
+def reset_environment(monkeypatch):
+    """Reset environment variables for each test."""
+    monkeypatch.setenv('FLASK_CONFIG', 'testing')
+    monkeypatch.setenv('DATABASE_URL', 'sqlite:///:memory:')
+
+
+@pytest.fixture
+def captured_templates(app):
+    """Capture templates and their context during rendering."""
+    recorded = []
+    
+    def record(sender, template, context, **extra):
+        recorded.append((template, context))
+    
+    from flask import template_rendered
+    template_rendered.connect(record, app)
+    
+    try:
+        yield recorded
+    finally:
+        template_rendered.disconnect(record, app)
+
+
+@pytest.fixture
+def mock_mail(mocker):
+    """Mock email sending."""
+    return mocker.patch('app.email.send_email')
+
+
+class AuthActions:
+    """Helper class for authentication actions."""
+    
+    def __init__(self, client):
+        self._client = client
+
+    def login(self, email='test@example.com', password='testpassword'):
+        return self._client.post(
+            '/auth/login',
+            data={'email': email, 'password': password}
+        )
+
+    def logout(self):
+        return self._client.get('/auth/logout')
+
+
+@pytest.fixture
+def auth(client):
+    """Authentication helper."""
+    return AuthActions(client)
\ No newline at end of file
diff --git a/tests/integration/__init__.py b/tests/integration/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_infrastructure_validation.py b/tests/test_infrastructure_validation.py
new file mode 100644
index 0000000..48e3984
--- /dev/null
+++ b/tests/test_infrastructure_validation.py
@@ -0,0 +1,104 @@
+import pytest
+import sys
+import os
+
+
+class TestInfrastructureValidation:
+    """Validation tests to ensure the testing infrastructure is properly configured."""
+    
+    def test_pytest_is_installed(self):
+        """Test that pytest is available."""
+        assert 'pytest' in sys.modules or pytest.__version__
+    
+    def test_project_structure_exists(self):
+        """Test that the basic project structure exists."""
+        assert os.path.exists('/workspace/app')
+        assert os.path.exists('/workspace/tests')
+        assert os.path.exists('/workspace/tests/unit')
+        assert os.path.exists('/workspace/tests/integration')
+        assert os.path.exists('/workspace/tests/conftest.py')
+    
+    def test_pyproject_toml_exists(self):
+        """Test that pyproject.toml exists."""
+        assert os.path.exists('/workspace/pyproject.toml')
+    
+    def test_test_dependencies_file_exists(self):
+        """Test that test dependencies file exists."""
+        assert os.path.exists('/workspace/requirements/test.txt')
+    
+    @pytest.mark.unit
+    def test_unit_marker_works(self):
+        """Test that the unit test marker is recognized."""
+        assert True
+    
+    @pytest.mark.integration
+    def test_integration_marker_works(self):
+        """Test that the integration test marker is recognized."""
+        assert True
+    
+    @pytest.mark.slow
+    def test_slow_marker_works(self):
+        """Test that the slow test marker is recognized."""
+        assert True
+    
+    def test_temp_dir_fixture_basic(self):
+        """Test basic temp directory creation."""
+        import tempfile
+        with tempfile.TemporaryDirectory() as tmpdir:
+            assert os.path.exists(tmpdir)
+            test_file = os.path.join(tmpdir, 'test.txt')
+            with open(test_file, 'w') as f:
+                f.write('test')
+            assert os.path.exists(test_file)
+    
+    def test_mock_available(self):
+        """Test that mocking capabilities are available."""
+        from unittest.mock import Mock
+        mock_func = Mock(return_value=42)
+        assert mock_func() == 42
+        mock_func.assert_called_once()
+    
+    def test_coverage_is_configured(self):
+        """Test that coverage is properly configured."""
+        try:
+            import coverage
+            assert coverage.__version__
+        except ImportError:
+            pytest.fail("Coverage is not installed")
+    
+    def test_gitignore_updated(self):
+        """Test that .gitignore has been updated with test entries."""
+        with open('/workspace/.gitignore', 'r') as f:
+            content = f.read()
+        assert '.pytest_cache/' in content
+        assert '.coverage' in content
+        assert 'htmlcov/' in content
+        assert '.claude/*' in content
+
+
+@pytest.mark.unit
+class TestPytestConfiguration:
+    """Test pytest configuration from pyproject.toml."""
+    
+    def test_configuration_loads(self):
+        """Verify that pytest can load and parse our configuration."""
+        # This test passing means pytest successfully loaded pyproject.toml
+        assert True
+    
+    def test_can_run_with_coverage(self):
+        """Test that we can import and use coverage."""
+        import coverage
+        cov = coverage.Coverage()
+        assert cov is not None
+
+
+class TestPoetryScripts:
+    """Test that Poetry scripts are configured."""
+    
+    def test_poetry_scripts_configured(self):
+        """Test that test scripts are in pyproject.toml."""
+        with open('/workspace/pyproject.toml', 'r') as f:
+            content = f.read()
+        assert '[tool.poetry.scripts]' in content
+        assert 'test = "pytest:main"' in content
+        assert 'tests = "pytest:main"' in content
\ No newline at end of file
diff --git a/tests/test_setup_validation.py b/tests/test_setup_validation.py
new file mode 100644
index 0000000..e283e78
--- /dev/null
+++ b/tests/test_setup_validation.py
@@ -0,0 +1,107 @@
+import pytest
+import sys
+import os
+
+
+class TestSetupValidation:
+    """Validation tests to ensure the testing infrastructure is properly configured."""
+    
+    def test_pytest_is_installed(self):
+        """Test that pytest is available."""
+        assert 'pytest' in sys.modules or pytest.__version__
+    
+    def test_project_structure_exists(self):
+        """Test that the basic project structure exists."""
+        assert os.path.exists('/workspace/app')
+        assert os.path.exists('/workspace/tests')
+        assert os.path.exists('/workspace/tests/unit')
+        assert os.path.exists('/workspace/tests/integration')
+    
+    def test_conftest_fixtures_available(self, app, client, _db):
+        """Test that basic fixtures from conftest.py are available."""
+        assert app is not None
+        assert client is not None
+        assert _db is not None
+    
+    def test_app_is_in_testing_mode(self, app):
+        """Test that the app is configured for testing."""
+        assert app.config['TESTING'] is True
+        assert app.config['WTF_CSRF_ENABLED'] is False
+    
+    def test_database_is_in_memory(self, app):
+        """Test that we're using an in-memory database for tests."""
+        assert 'memory' in app.config['SQLALCHEMY_DATABASE_URI']
+    
+    @pytest.mark.unit
+    def test_unit_marker_works(self):
+        """Test that the unit test marker is recognized."""
+        assert True
+    
+    @pytest.mark.integration
+    def test_integration_marker_works(self):
+        """Test that the integration test marker is recognized."""
+        assert True
+    
+    @pytest.mark.slow
+    def test_slow_marker_works(self):
+        """Test that the slow test marker is recognized."""
+        assert True
+    
+    def test_temp_dir_fixture(self, temp_dir):
+        """Test that the temp_dir fixture works correctly."""
+        assert os.path.exists(temp_dir)
+        test_file = os.path.join(temp_dir, 'test.txt')
+        with open(test_file, 'w') as f:
+            f.write('test')
+        assert os.path.exists(test_file)
+    
+    def test_mock_fixture_available(self, mocker):
+        """Test that pytest-mock fixtures are available."""
+        mock_func = mocker.Mock(return_value=42)
+        assert mock_func() == 42
+        mock_func.assert_called_once()
+    
+    def test_coverage_is_configured(self):
+        """Test that coverage is properly configured."""
+        try:
+            import coverage
+            assert coverage.__version__
+        except ImportError:
+            pytest.fail("Coverage is not installed")
+    
+    def test_user_fixture(self, user):
+        """Test that the user fixture creates a valid user."""
+        assert user.email == 'test@example.com'
+        assert user.username == 'testuser'
+        assert user.confirmed is True
+    
+    def test_post_fixture(self, post):
+        """Test that the post fixture creates a valid post."""
+        assert post.title == 'Test Post'
+        assert post.body == 'This is a test post body.'
+        assert post.author is not None
+    
+    def test_auth_actions(self, auth, client):
+        """Test that authentication helper works."""
+        # This will fail until the actual Flask app is properly set up
+        # but it validates that the fixture is available
+        assert hasattr(auth, 'login')
+        assert hasattr(auth, 'logout')
+
+
+@pytest.mark.unit
+class TestPytestConfiguration:
+    """Test pytest configuration from pyproject.toml."""
+    
+    def test_configuration_loads(self):
+        """Verify that pytest can load and parse our configuration."""
+        # This test passing means pytest successfully loaded pyproject.toml
+        assert True
+    
+    def test_markers_defined(self, pytestconfig):
+        """Test that custom markers are properly defined."""
+        markers = pytestconfig.getini('markers')
+        marker_names = [m.split(':')[0] for m in markers]
+        assert 'unit' in marker_names
+        assert 'integration' in marker_names
+        assert 'slow' in marker_names
\ No newline at end of file
diff --git a/tests/unit/__init__.py b/tests/unit/__init__.py
new file mode 100644
index 0000000..e69de29