test: add unit test for both parts

internal/2016/DayThree/code_test.go

@@ -0,0 +1,28 @@
+package daythree
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	input := [][3]int{{5, 10, 25}}
+	expected := 0
+	got := PartOne(input)
+	if got != expected {
+		t.Errorf("PartOne() = %d, want %d", got, expected)
+	}
+}
+
+func TestPartTwo(t *testing.T) {
+	input := [][3]int{
+		{101, 301, 501},
+		{102, 302, 502},
+		{103, 303, 503},
+		{201, 401, 601},
+		{202, 402, 602},
+		{203, 403, 603},
+	}
+	expected := 6
+	got := PartTwo(input)
+	if got != expected {
+		t.Errorf("PartTwo() = %d, want %d", got, expected)
+	}
+}