package main

import (
	"testing"
	"time"
)

func TestRemainingFrameTime(t *testing.T) {
	start := time.Date(2026, time.September, 2, 0, 0, 0, 0, time.UTC)
	interval := 16 * time.Millisecond
	tests := []struct {
		name    string
		elapsed time.Duration
		want    time.Duration
	}{
		{name: "no work", want: interval},
		{name: "partial budget", elapsed: 5 * time.Millisecond, want: 11 * time.Millisecond},
		{name: "exact budget", elapsed: interval},
		{name: "over budget", elapsed: 20 * time.Millisecond},
	}
	for _, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			got := remainingFrameTime(start, start.Add(test.elapsed), interval)
			if got != test.want {
				t.Fatalf("remainingFrameTime() = %v, want %v", got, test.want)
			}
		})
	}
}