test: add unit test for part two

internal/2017/DayOne/code_test.go

@@ -39,3 +39,46 @@ func TestPartOne(t *testing.T) {
 		})
 	}
 }
+
+func TestPartTwo(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    []int
+		expected int
+	}{
+		{
+			name:     "1212 produces 6",
+			input:    []int{1, 2, 1, 2},
+			expected: 6,
+		},
+		{
+			name:     "1221 produces 0",
+			input:    []int{1, 2, 2, 1},
+			expected: 0,
+		},
+		{
+			name:     "123425 produces 4",
+			input:    []int{1, 2, 3, 4, 2, 5},
+			expected: 4,
+		},
+		{
+			name:     "123123 produces 12",
+			input:    []int{1, 2, 3, 1, 2, 3},
+			expected: 12,
+		},
+		{
+			name:     "12131415 produces 4",
+			input:    []int{1, 2, 1, 3, 1, 4, 1, 5},
+			expected: 4,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartTwo(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartTwo() = %d, want %d", got, tt.expected)
+			}
+		})
+	}
+}