test: add unit test for p1

internal/2015/DayThree/code_test.go

@@ -0,0 +1,24 @@
+package daythree
+
+import "testing"
+
+func TestPartOne(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected int
+	}{
+		{">", ">", 2},
+		{"^>v<", "^>v<", 4},
+		{"^v^v^v^v^v", "^v^v^v^v^v", 2},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := PartOne(tt.input)
+			if got != tt.expected {
+				t.Errorf("PartOne(%q) = %d, want %d", tt.input, got, tt.expected)
+			}
+		})
+	}
+}