diff --git a/day03/classes.py b/day03/classes.py
index f6d007f..2181abd 100644
--- a/day03/classes.py
+++ b/day03/classes.py
@@ -126,3 +126,7 @@ def find_gear_parts(
             if part_number.touching(gear.col, gear.row, self.row_size):
                 result.append(part_number)
         return result
+
+    def filter_engine_parts(self, part_numbers: list[PartNumber]) -> list[PartNumber]:
+        """Return the legit part numbers"""
+        return list(filter(self.is_engine_part, part_numbers))
diff --git a/day03/day3.py b/day03/day3.py
index 9bde5d7..b92dcb6 100644
--- a/day03/day3.py
+++ b/day03/day3.py
@@ -2,37 +2,40 @@
 Day 3 implementation
 """
 
-from typing import TYPE_CHECKING
 
-from day03.classes import Gear, Matrix
+from day03.classes import Gear, Matrix, PartNumber
 
-if TYPE_CHECKING:
-    from day03.classes import PartNumber
+INPUT = "day03/input.txt"
+INPUT_SMALL = "day03/input-small.txt"
 
 
-def get_data() -> Matrix:
+def get_data(path: str) -> Matrix:
     """Convert text file to matrix"""
-    with open("day03/input.txt", "r", encoding="utf8") as file:
+    with open(path, "r", encoding="utf8") as file:
         data = file.readlines()
         data = [line.strip() for line in data]
     return Matrix(data=data)
 
 
-def main() -> None:
-    matrix = get_data()
-    part_numbers = matrix.get_part_numbers()
+def part1(part_numbers: list[PartNumber]) -> int:
+    return sum([part_number.value for part_number in part_numbers])
+
+
+def part2(part_numbers: list[PartNumber], matrix: Matrix) -> int:
+    gears: list[Gear] = matrix.get_gears(part_numbers)
+    return sum(gear.gear_ratio for gear in gears)
 
-    def part_filter(part_number: "PartNumber") -> bool:
-        return matrix.is_engine_part(part_number)
 
-    part_numbers = list(filter(part_filter, part_numbers))
+def main() -> None:
+    matrix: Matrix = get_data(INPUT)
+    part_numbers: list["PartNumber"] = matrix.get_part_numbers()
+    part_numbers = matrix.filter_engine_parts(part_numbers)
 
     # q1
-    print(sum([part_number.value for part_number in part_numbers]))
+    print(part1(part_numbers))
 
     # q2
-    gears: list[Gear] = matrix.get_gears(part_numbers)
-    print(sum(gear.gear_ratio for gear in gears))
+    print(part2(part_numbers, matrix))
 
 
 if __name__ == "__main__":
diff --git a/day03/input-small.txt b/day03/input-small.txt
new file mode 100644
index 0000000..b20187f
--- /dev/null
+++ b/day03/input-small.txt
@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..
diff --git a/day03/tests/__init__.py b/day03/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/day03/tests/test_classes.py b/day03/tests/test_classes.py
new file mode 100644
index 0000000..fc44553
--- /dev/null
+++ b/day03/tests/test_classes.py
@@ -0,0 +1,35 @@
+from dataclasses import dataclass
+
+from day03.classes import PartNumber
+
+
+@dataclass
+class PartNumberTouchTest:
+    col: int
+    row: int
+    row_size: int
+    result: bool
+
+
+def test_part_number() -> None:
+    part_number = PartNumber(0, 0, 3, 467)
+
+    assert part_number.end_index == 3
+
+    tests = [
+        PartNumberTouchTest(0, 0, 10, True),
+        PartNumberTouchTest(0, 0, 10, True),
+        PartNumberTouchTest(1, 0, 10, True),
+        PartNumberTouchTest(2, 0, 10, True),
+        PartNumberTouchTest(3, 0, 10, True),
+        PartNumberTouchTest(0, 0, 10, True),
+        PartNumberTouchTest(1, 1, 10, True),
+        PartNumberTouchTest(2, 1, 10, True),
+        PartNumberTouchTest(3, 1, 10, True),
+        PartNumberTouchTest(1, -1, 10, True),
+        PartNumberTouchTest(2, -1, 10, True),
+        PartNumberTouchTest(3, -1, 10, True),
+        PartNumberTouchTest(4, 0, 10, False),
+    ]
+    for test in tests:
+        assert part_number.touching(test.col, test.row, test.row_size) == test.result