From 7bb49794297b46aa1c577e89da24d39b4348c6d4 Mon Sep 17 00:00:00 2001
From: batsumaru <>
Date: Sun, 9 Aug 2026 12:39:50 +0900
Subject: Added fp_t multiplication

---
 tests/test_fixed_point.cpp | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'tests/test_fixed_point.cpp')

diff --git a/tests/test_fixed_point.cpp b/tests/test_fixed_point.cpp
index b116340..6d1a594 100644
--- a/tests/test_fixed_point.cpp
+++ b/tests/test_fixed_point.cpp
@@ -17,6 +17,13 @@ TEST_CASE("fp_t subtraction anti-commutative") {
     REQUIRE(a.raw != 0);
 }
 
+TEST_CASE("fp_t multiplication is commutative") {
+    fp_t a = fp_t::from_int(2);
+    fp_t b = fp_t::from_int(5);
+    CHECK(a * b == b * a);
+    REQUIRE(a.raw != 1);
+}
+
 TEST_CASE("fp_t addition overflows") {
     fp_t a = fp_t::from_raw(INT32_MAX);
     fp_t b = fp_t::from_raw(1);
@@ -30,3 +37,16 @@ TEST_CASE("fp_t subtraction underflows") {
     fp_t c = fp_t::from_raw(INT32_MAX);
     CHECK(a - b == c);
 }
+
+TEST_CASE("fp_t multiplication overflows") {
+    fp_t a = fp_t::from_raw(INT32_MAX);
+    fp_t b = fp_t::from_int(2);
+    fp_t c = fp_t::from_raw(-2);
+    CHECK(a * b == c);
+}
+
+TEST_CASE("fp_t multiplication drops percision under 1 ULP") {
+    fp_t a = fp_t::from_raw(1);
+    fp_t b = fp_t::from_raw(0);
+    CHECK(a * a == b);
+}
-- 
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