test: add unit test for part one

internal/2016/DayOne/code_test.go

@@ -0,0 +1,38 @@
+package dayone
+
+import (
+	"testing"
+)
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []string
+		expected int
+	}{
+		{
+			name:     "Example 1",
+			input:    []string{"R2", "L3"},
+			expected: 5,
+		},
+		{
+			name:     "Example 2",
+			input:    []string{"R2", "R2", "R2"},
+			expected: 2,
+		},
+		{
+			name:     "Example 3",
+			input:    []string{"R5", "L5", "R5", "R3"},
+			expected: 12,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartOne() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}