test: add unit tests

2021/day02/go.mod

@@ -0,0 +1,3 @@
+module 2021/day02
+
+go 1.25.4

2021/day02/main.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func parseInput(file string) []string {
+	content, err := os.ReadFile(file)
+	if err != nil {
+		log.Fatalf("Failed to read input file: %v", err)
+	}
+	return strings.Split(string(content), "\n")
+}
+
+func PartOne(data []string) int {
+	horizontal := 0
+	depth := 0
+	for _, line := range data {
+		parts := strings.Split(line, " ")
+		direction := parts[0]
+		amount, _ := strconv.Atoi(parts[1])
+		switch direction {
+		case "forward":
+			horizontal += amount
+		case "down":
+			depth += amount
+		case "up":
+			depth -= amount
+		}
+	}
+	return horizontal * depth
+}
+
+func PartTwo(data []string) int {
+	horizontal := 0
+	depth := 0
+	aim := 0
+
+	for _, line := range data {
+		parts := strings.Split(line, " ")
+		direction := parts[0]
+		amount, _ := strconv.Atoi(parts[1])
+
+		switch direction {
+		case "forward":
+			horizontal += amount
+			depth += aim * amount
+		case "down":
+			aim += amount
+		case "up":
+			aim -= amount
+		}
+	}
+	return horizontal * depth
+}
+
+func main() {
+	data := parseInput("input.txt")
+	fmt.Println("Part 1:", PartOne(data))
+	fmt.Println("Part 2:", PartTwo(data))
+}

2021/day02/main_test.go

@@ -0,0 +1,28 @@
+package main
+
+import "testing"
+
+var testInput = []string{
+	"forward 5",
+	"down 5",
+	"forward 8",
+	"up 3",
+	"down 8",
+	"forward 2",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 150
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 900
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}