test: add unit test for p1

internal/2015/DayTwo/code_test.go

@@ -0,0 +1,23 @@
+package daytwo
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{"2x3x4", "2x3x4", 58},
+		{"1x1x10", "1x1x10", 43},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne([]string{tt.input})
+			if got != tt.expected {
+				t.Errorf("PartOne(%q) = %d, want %d", tt.input, got, tt.expected)
+			}
+		})
+	}
+}