refactor: massive refactor to have only one binary to call

internal/2020/DayOne/code_test.go

@@ -0,0 +1,22 @@
+package dayone
+
+import "testing"
+
+var testInput = []int{1721, 979, 366, 299, 675, 1456}
+
+func TestPartOne(t *testing.T) {
+	expected := 514579
+	got := PartOne(testInput)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	expected := 241861950
+	got := PartTwo(testInput)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}
+