From a0e606a2c0f3a891ebd0270c0dd4eb5998e1e456 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vojt=C4=9Bch=20Michal?= <vojta.michall@email.cz>
Date: Thu, 18 Dec 2025 01:25:44 +0100
Subject: [PATCH 1/2] Add <flat_set> test to test_header_units_and_modules.hpp

---
 .../include/test_header_units_and_modules.hpp | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/tests/std/include/test_header_units_and_modules.hpp b/tests/std/include/test_header_units_and_modules.hpp
index 0e08cfe0cd5..3d6ace99e9f 100644
--- a/tests/std/include/test_header_units_and_modules.hpp
+++ b/tests/std/include/test_header_units_and_modules.hpp
@@ -269,7 +269,24 @@ void test_flat_set() {
     using namespace std;
     puts("Testing <flat_set>.");
 
-    // FIXME! ADD TEST COVERAGE HERE!
+    [[maybe_unused]] constexpr sorted_unique_t unique_tag         = sorted_unique;
+    [[maybe_unused]] constexpr sorted_equivalent_t equivalent_tag = sorted_equivalent;
+
+    constexpr auto simple_truth = [](const auto&) { return true; };
+
+    flat_set<int> fs;
+    fs.emplace(42);
+    fs.emplace(42);
+    assert(fs.size() == 1);
+    assert(erase_if(fs, simple_truth) == 1);
+    assert(fs.empty());
+
+    flat_multiset<int> fss;
+    fss.emplace(42);
+    fss.emplace(42);
+    assert(fss.size() == 2);
+    assert(erase_if(fss, simple_truth) == 2);
+    assert(fss.empty());
 }
 #endif // TEST_STANDARD >= 23
 

From b929a5dc4a778300aeebcfb5a43b20012bf12e03 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@microsoft.com>
Date: Mon, 5 Jan 2026 05:59:51 -0800
Subject: [PATCH 2/2] `fss` => `fms`

---
 tests/std/include/test_header_units_and_modules.hpp | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/tests/std/include/test_header_units_and_modules.hpp b/tests/std/include/test_header_units_and_modules.hpp
index 3d6ace99e9f..71aaf6a6632 100644
--- a/tests/std/include/test_header_units_and_modules.hpp
+++ b/tests/std/include/test_header_units_and_modules.hpp
@@ -281,12 +281,12 @@ void test_flat_set() {
     assert(erase_if(fs, simple_truth) == 1);
     assert(fs.empty());
 
-    flat_multiset<int> fss;
-    fss.emplace(42);
-    fss.emplace(42);
-    assert(fss.size() == 2);
-    assert(erase_if(fss, simple_truth) == 2);
-    assert(fss.empty());
+    flat_multiset<int> fms;
+    fms.emplace(42);
+    fms.emplace(42);
+    assert(fms.size() == 2);
+    assert(erase_if(fms, simple_truth) == 2);
+    assert(fms.empty());
 }
 #endif // TEST_STANDARD >= 23