From a3466f49dc40e432ca1a5ac5c97640b8f476063b Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Fri, 22 May 2026 14:46:30 +0000
Subject: [PATCH] Add tests for isinr and icosr scaling functions

Co-authored-by: perim <436583+perim@users.noreply.github.com>
---
 tests/test_direction.cpp | 31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/tests/test_direction.cpp b/tests/test_direction.cpp
index 41483c9..9a2663e 100644
--- a/tests/test_direction.cpp
+++ b/tests/test_direction.cpp
@@ -30,5 +30,36 @@ int main()
 	printf("min: %i max: %i\n", min, max);
 	assert(min <= 2 && max <= 2);
 
+	const int distances[] = {0, 1, 10, 100, 1000, 10000, 65536, 100000, 1000000};
+	for (int dist : distances)
+	{
+		int32_t rmax = 0, rmin = 0;
+		for (int i = 0; i <= UINT16_MAX; i++)
+		{
+			double exact = dist * sin(2 * M_PI * i / 65536.0) / 16.0;
+			int s = lround(exact);
+			int s5d = isinr(i, dist);
+			int err = s - s5d;
+			if (err > rmax) rmax = err;
+			if (err < rmin) rmin = err;
+		}
+		int limit = dist > 0 ? (dist * 2 / 65536) + 2 : 0;
+		printf("isinr dist %i min: %i max: %i (limit: %i)\n", dist, rmin, rmax, limit);
+		assert(rmin >= -limit && rmax <= limit);
+
+		rmax = 0; rmin = 0;
+		for (int i = 0; i <= UINT16_MAX; i++)
+		{
+			double exact = dist * cos(2 * M_PI * i / 65536.0) / 16.0;
+			int c = lround(exact);
+			int c5d = icosr(i, dist);
+			int err = c - c5d;
+			if (err > rmax) rmax = err;
+			if (err < rmin) rmin = err;
+		}
+		printf("icosr dist %i min: %i max: %i (limit: %i)\n", dist, rmin, rmax, limit);
+		assert(rmin >= -limit && rmax <= limit);
+	}
+
 	return 0;
 }