Improve test coverance and fixes according to tests

app/tests/conftest.py

@@ -2,6 +2,7 @@
 
 import pytest
 from sqlalchemy import create_engine
+from sqlalchemy.pool import StaticPool
 from sqlalchemy.orm import sessionmaker
 from fastapi.testclient import TestClient
 
@@ -9,21 +10,18 @@ from app.main import app
 from app.db.base import Base
 from app.db.session import get_db
 
+import os
+os.environ["TESTING"] = "1"
 
 # Use in-memory SQLite for tests
 TEST_DATABASE_URL = "sqlite+pysqlite:///:memory:"
 
-
 @pytest.fixture(scope="function")
 def db_session():
-    """
-    Creates a new database session for a test.
-    Rolls back everything after test finishes.
-    """
-
     engine = create_engine(
         TEST_DATABASE_URL,
         connect_args={"check_same_thread": False},
+        poolclass=StaticPool,
     )
 
     TestingSessionLocal = sessionmaker(
@@ -32,7 +30,6 @@ def db_session():
         bind=engine,
     )
 
-    # Create tables
     Base.metadata.create_all(bind=engine)
 
     db = TestingSessionLocal()

app/tests/test_config.py

@@ -0,0 +1,16 @@
+from app.core.config import get_settings
+
+def test_get_settings_returns_same_instance():
+    s1 = get_settings()
+    s2 = get_settings()
+
+    assert s1 is s2  # lru_cache should return same instance
+
+def test_default_settings_values():
+    settings = get_settings()
+
+    assert settings.app_name == "URL Shortener"
+    assert settings.host == "0.0.0.0"
+    assert settings.port == 8000
+    assert settings.debug is True
+    assert isinstance(settings.allowed_hosts, list)

app/tests/test_models.py

@@ -0,0 +1,32 @@
+from app.db.models import URL
+
+def test_url_model_defaults(db_session):
+    url = URL(
+        short_code="abc123",
+        original_url="https://example.com",
+    )
+
+    db_session.add(url)
+    db_session.commit()
+    db_session.refresh(url)
+
+    assert url.id is not None
+    assert url.clicks == 0
+    assert url.created_at is not None
+    assert url.last_accessed is None
+
+def test_url_repr(db_session):
+    url = URL(
+        short_code="xyz789",
+        original_url="https://repr-test.com",
+    )
+
+    db_session.add(url)
+    db_session.commit()
+    db_session.refresh(url)
+
+    repr_output = repr(url)
+
+    assert "URL" in repr_output
+    assert "xyz789" in repr_output
+    assert "https://repr-test.com" in repr_output

app/tests/test_routes.py

@@ -1,8 +1,5 @@
 # app/tests/test_routes.py
 
-import pytest
-
-
 def test_home(client):
     response = client.get("/")
     assert response.status_code == 200

app/tests/test_services.py

@@ -0,0 +1,106 @@
+import pytest
+from unittest.mock import patch
+
+from app.services import url_service
+from app.db.models import URL
+
+
+def test_create_short_url_creates_new(db_session):
+    short_url = url_service.create_short_url(
+        db_session,
+        "https://new-url.com",
+    )
+
+    assert short_url.startswith("http://")
+
+    entry = db_session.query(URL).first()
+    assert entry is not None
+    assert entry.original_url == "https://new-url.com"
+
+
+def test_create_short_url_returns_existing(db_session):
+    first = url_service.create_short_url(
+        db_session,
+        "https://duplicate.com",
+    )
+
+    second = url_service.create_short_url(
+        db_session,
+        "https://duplicate.com",
+    )
+
+    assert first == second
+    assert db_session.query(URL).count() == 1
+
+
+def test_create_short_url_collision_failure(db_session):
+    with patch(
+        "app.services.url_service.generate_short_code",
+        return_value="fixedcode",
+    ):
+        # First insert works
+        url_service.create_short_url(db_session, "https://a.com")
+
+        # Force collision repeatedly
+        with pytest.raises(RuntimeError):
+            url_service.create_short_url(db_session, "https://b.com")
+
+
+def test_get_original_url_success(db_session):
+    short_url = url_service.create_short_url(
+        db_session,
+        "https://lookup.com",
+    )
+    code = short_url.split("/")[-1]
+
+    original = url_service.get_original_url(db_session, code)
+
+    assert original == "https://lookup.com"
+
+
+def test_get_original_url_not_found(db_session):
+    result = url_service.get_original_url(db_session, "missing")
+    assert result is None
+
+
+def test_increment_clicks_success(db_session):
+    short_url = url_service.create_short_url(
+        db_session,
+        "https://click-test.com",
+    )
+    code = short_url.split("/")[-1]
+
+    success = url_service.increment_clicks(db_session, code)
+
+    assert success is True
+
+    entry = db_session.query(URL).first()
+    assert entry.clicks == 1
+    assert entry.last_accessed is not None
+
+
+def test_increment_clicks_not_found(db_session):
+    result = url_service.increment_clicks(db_session, "missing")
+    assert result is False
+
+
+def test_get_stats_success(db_session):
+    short_url = url_service.create_short_url(
+        db_session,
+        "https://stats.com",
+    )
+    code = short_url.split("/")[-1]
+
+    url_service.increment_clicks(db_session, code)
+
+    stats = url_service.get_stats(db_session, code)
+
+    assert stats is not None
+    assert stats["original_url"] == "https://stats.com"
+    assert stats["clicks"] == 1
+    assert stats["created_at"] is not None
+
+
+def test_get_stats_not_found(db_session):
+    stats = url_service.get_stats(db_session, "missing")
+    assert stats is None

app/tests/test_utils.py

@@ -0,0 +1,19 @@
+import string
+from app.utils.short_code import generate_short_code
+
+def test_generate_short_code_length():
+    code = generate_short_code(8)
+    assert len(code) == 8
+
+def test_generate_short_code_is_alphanumeric():
+    code = generate_short_code(12)
+    allowed = string.ascii_letters + string.digits
+
+    for char in code:
+        assert char in allowed
+
+def test_generate_short_code_randomness():
+    code1 = generate_short_code()
+    code2 = generate_short_code()
+
+    assert code1 != code2  # extremely unlikely to fail