diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 00000000..d92458d3
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,24 @@
+from pathlib import Path
+
+import pytest
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+DATA_DIR = REPO_ROOT / "data"
+
+
+@pytest.fixture()
+def sales_data_csv(tmp_path: Path) -> Path:
+    """Return a temporary copy of ``sales_data.csv``."""
+    src = DATA_DIR / "sales_data.csv"
+    dst = tmp_path / "sales_data.csv"
+    dst.write_text(src.read_text())
+    return dst
+
+
+@pytest.fixture()
+def insurance_sales_csv(tmp_path: Path) -> Path:
+    """Return a temporary copy of ``insurance_sales.csv``."""
+    src = DATA_DIR / "insurance_sales.csv"
+    dst = tmp_path / "insurance_sales.csv"
+    dst.write_text(src.read_text())
+    return dst
diff --git a/tests/test_business_tools.py b/tests/test_business_tools.py
index 5a7e26ee..1ef4ad6b 100644
--- a/tests/test_business_tools.py
+++ b/tests/test_business_tools.py
@@ -1,10 +1,10 @@
 
-import os
 import sys
+from pathlib import Path
 
 # Ensure the repository root is on sys.path so business_tools can be imported
-REPO_ROOT = os.path.abspath(os.path.join(os.path.dirname(__file__), os.pardir))
-sys.path.insert(0, os.path.join(REPO_ROOT, "src"))
+REPO_ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(REPO_ROOT / "src"))
 
 from business_tools import (  # noqa: E402
     calculate_profit,
@@ -18,57 +18,39 @@
 )
 
 
-def test_calculate_profit():
+def test_calculate_profit() -> None:
     assert calculate_profit(1000, 600) == 400
 
 
-def test_get_sales_from_csv(tmp_path):
-    # copy sample sales_data.csv to a temp directory to avoid modifying repo file
-    src = os.path.join(REPO_ROOT, 'data', 'sales_data.csv')
-    dst = tmp_path / 'sales_data.csv'
-    with open(src, 'r') as fsrc, open(dst, 'w') as fdst:
-        fdst.write(fsrc.read())
-    assert get_sales_from_csv(str(dst)) == 950
+def test_get_sales_from_csv(sales_data_csv: Path) -> None:
+    """Verify reading the sales CSV sums correctly."""
+    assert get_sales_from_csv(str(sales_data_csv)) == 950
 
 
-def test_calculate_commission():
-    premiums = [300, 700, 200]
+def test_calculate_commission() -> None:
+    premiums = [300.0, 700.0, 200.0]
     assert calculate_commission(premiums, rate=0.1) == 120.0
 
 
-def test_load_insurance_sales_and_total_commission(tmp_path):
-    src = os.path.join(REPO_ROOT, "data", "insurance_sales.csv")
-    dst = tmp_path / "insurance_sales.csv"
-    with open(src, "r") as fsrc, open(dst, "w") as fdst:
-        fdst.write(fsrc.read())
-    records = load_insurance_sales(str(dst))
+def test_load_insurance_sales_and_total_commission(
+    insurance_sales_csv: Path,
+) -> None:
+    records = load_insurance_sales(str(insurance_sales_csv))
     assert len(records) == 15
     assert total_commission(records) == 2545.0
 
 
-def test_filter_by_state(tmp_path):
-    src = os.path.join(REPO_ROOT, "data", "insurance_sales.csv")
-    dst = tmp_path / "insurance_sales.csv"
-    with open(src, "r") as fsrc, open(dst, "w") as fdst:
-        fdst.write(fsrc.read())
-    records = load_insurance_sales(str(dst))
+def test_filter_by_state(insurance_sales_csv: Path) -> None:
+    records = load_insurance_sales(str(insurance_sales_csv))
     ca_records = filter_by_state(records, "CA")
     assert len(ca_records) == 4
 
-def test_calculate_total_premium(tmp_path):
-    src = os.path.join(REPO_ROOT, "data", "insurance_sales.csv")
-    dst = tmp_path / "insurance_sales.csv"
-    with open(src, "r") as fsrc, open(dst, "w") as fdst:
-        fdst.write(fsrc.read())
-    records = load_insurance_sales(str(dst))
+def test_calculate_total_premium(insurance_sales_csv: Path) -> None:
+    records = load_insurance_sales(str(insurance_sales_csv))
     assert calculate_total_premium(records) == 18480.0
 
 
-def test_filter_policies_by_state(tmp_path):
-    src = os.path.join(REPO_ROOT, "data", "insurance_sales.csv")
-    dst = tmp_path / "insurance_sales.csv"
-    with open(src, "r") as fsrc, open(dst, "w") as fdst:
-        fdst.write(fsrc.read())
-    records = load_insurance_sales(str(dst))
+def test_filter_policies_by_state(insurance_sales_csv: Path) -> None:
+    records = load_insurance_sales(str(insurance_sales_csv))
     ca_records = filter_policies_by_state(records, "CA")
     assert len(ca_records) == 4
diff --git a/tests/test_cli.py b/tests/test_cli.py
index 0b4ef07e..8075c1d5 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -13,21 +13,15 @@ def run_cli(args: list[str]) -> str:
     return result.strip()
 
 
-def test_profit_cli():
+def test_profit_cli() -> None:
     assert run_cli(["profit", "100", "40"]) == "60"
 
 
-def test_commission_cli(tmp_path: Path):
-    src = REPO_ROOT / "data" / "insurance_sales.csv"
-    dst = tmp_path / "insurance_sales.csv"
-    dst.write_text(src.read_text())
-    out = run_cli(["commission", str(dst)])
+def test_commission_cli(insurance_sales_csv: Path) -> None:
+    out = run_cli(["commission", str(insurance_sales_csv)])
     assert out == "2545.0"
 
 
-def test_premium_cli(tmp_path: Path):
-    src = REPO_ROOT / "data" / "insurance_sales.csv"
-    dst = tmp_path / "insurance_sales.csv"
-    dst.write_text(src.read_text())
-    out = run_cli(["premium", str(dst)])
+def test_premium_cli(insurance_sales_csv: Path) -> None:
+    out = run_cli(["premium", str(insurance_sales_csv)])
     assert out == "18480.0"