test: add unit test for part one

2020/day06/go.mod

@@ -0,0 +1,3 @@
+module 2020/day06
+
+go 1.25.4

2020/day06/main.go

@@ -0,0 +1,45 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"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(strings.TrimSpace(string(content)), "\n")
+}
+
+func PartOne(input []string) int {
+	total := 0
+	groupAnswers := make(map[rune]bool)
+
+	for i, line := range input {
+		if line != "" {
+			for _, char := range line {
+				if char >= 'a' && char <= 'z' {
+					groupAnswers[char] = true
+				}
+			}
+		}
+
+		if line == "" || i == len(input)-1 {
+			total += len(groupAnswers)
+			groupAnswers = make(map[rune]bool)
+		}
+	}
+
+	total += len(groupAnswers)
+
+	return total
+}
+
+func main() {
+	input := parseInput("input.txt")
+	fmt.Println("Part 1:", PartOne(input))
+}

2020/day06/main_test.go

@@ -0,0 +1,29 @@
+package main
+
+import "testing"
+
+var input = []string{
+	"abc",
+	"",
+	"a",
+	"b",
+	"c",
+	"",
+	"ab",
+	"ac",
+	"",
+	"a",
+	"a",
+	"a",
+	"a",
+	"",
+	"b",
+}
+
+func TestPartOne(t *testing.T) {
+	expected := 11
+	got := PartOne(input)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}