diff --git a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/ranges_unique_copy.pass.cpp b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/ranges_unique_copy.pass.cpp
index b84600b92c2b2..a4cf97069c96a 100644
--- a/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/ranges_unique_copy.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.modifying.operations/alg.unique/ranges_unique_copy.pass.cpp
@@ -418,7 +418,7 @@ constexpr bool test() {
       assert(std::ranges::equal(out, expected));
       assert(base(result.in) == in.end());
       assert(base(result.out) == out.end());
-      assert(numberOfComp == in.size() - 1);
+      assert(numberOfComp == static_cast<int>(in.size() - 1));
       assert(numberOfProj <= static_cast<int>(2 * (in.size() - 1)));
     }
     // range overload
@@ -434,7 +434,7 @@ constexpr bool test() {
       assert(std::ranges::equal(out, expected));
       assert(base(result.in) == in.end());
       assert(base(result.out) == out.end());
-      assert(numberOfComp == in.size() - 1);
+      assert(numberOfComp == static_cast<int>(in.size() - 1));
       assert(numberOfProj <= static_cast<int>(2 * (in.size() - 1)));
     }
   }
diff --git a/libcxx/test/std/containers/sequences/insert_range_sequence_containers.h b/libcxx/test/std/containers/sequences/insert_range_sequence_containers.h
index b77b2510eae23..352ee474cae76 100644
--- a/libcxx/test/std/containers/sequences/insert_range_sequence_containers.h
+++ b/libcxx/test/std/containers/sequences/insert_range_sequence_containers.h
@@ -427,7 +427,8 @@ template <> constexpr TestCase<int> FullContainer_End_LongRange<bool> {
 template <class Container, class Iter, class Sent, class Validate>
 constexpr void test_sequence_insert_range(Validate validate) {
   using T = typename Container::value_type;
-  auto get_pos = [](auto& c, auto& test_case) { return std::ranges::next(c.begin(), test_case.index); };
+  using D      = typename Container::difference_type;
+  auto get_pos = [](auto& c, auto& test_case) { return std::ranges::next(c.begin(), static_cast<D>(test_case.index)); };
 
   auto test = [&](auto& test_case) {
     Container c(test_case.initial.begin(), test_case.initial.end());
diff --git a/libcxx/test/std/containers/unord/unord.map/eq.different_hash.pass.cpp b/libcxx/test/std/containers/unord/unord.map/eq.different_hash.pass.cpp
index 52a806f04d72d..94de7589eb060 100644
--- a/libcxx/test/std/containers/unord/unord.map/eq.different_hash.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.map/eq.different_hash.pass.cpp
@@ -36,7 +36,7 @@ std::size_t hash_neg(T val) {
 }
 template <class T>
 std::size_t hash_scale(T val) {
-  return val << 1;
+  return static_cast<std::size_t>(val << 1);
 }
 template <class T>
 std::size_t hash_even(T val) {
@@ -57,7 +57,7 @@ std::size_t hash_neg(T* val) {
 }
 template <class T>
 std::size_t hash_scale(T* val) {
-  return *val << 1;
+  return static_cast<std::size_t>(*val << 1);
 }
 template <class T>
 std::size_t hash_even(T* val) {
diff --git a/libcxx/test/std/containers/unord/unord.multimap/eq.different_hash.pass.cpp b/libcxx/test/std/containers/unord/unord.multimap/eq.different_hash.pass.cpp
index 2644c96576446..0aafb401d42ca 100644
--- a/libcxx/test/std/containers/unord/unord.multimap/eq.different_hash.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.multimap/eq.different_hash.pass.cpp
@@ -37,7 +37,7 @@ std::size_t hash_neg(T val) {
 }
 template <class T>
 std::size_t hash_scale(T val) {
-  return val << 1;
+  return static_cast<std::size_t>(val << 1);
 }
 template <class T>
 std::size_t hash_even(T val) {
@@ -58,7 +58,7 @@ std::size_t hash_neg(T* val) {
 }
 template <class T>
 std::size_t hash_scale(T* val) {
-  return *val << 1;
+  return static_cast<std::size_t>(*val << 1);
 }
 template <class T>
 std::size_t hash_even(T* val) {
diff --git a/libcxx/test/std/containers/unord/unord.multiset/eq.different_hash.pass.cpp b/libcxx/test/std/containers/unord/unord.multiset/eq.different_hash.pass.cpp
index 9f53e8d79e866..5b8f11e929279 100644
--- a/libcxx/test/std/containers/unord/unord.multiset/eq.different_hash.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.multiset/eq.different_hash.pass.cpp
@@ -36,7 +36,7 @@ std::size_t hash_neg(T val) {
 }
 template <class T>
 std::size_t hash_scale(T val) {
-  return val << 1;
+  return static_cast<std::size_t>(val << 1);
 }
 template <class T>
 std::size_t hash_even(T val) {
@@ -57,7 +57,7 @@ std::size_t hash_neg(T* val) {
 }
 template <class T>
 std::size_t hash_scale(T* val) {
-  return *val << 1;
+  return static_cast<std::size_t>(*val << 1);
 }
 template <class T>
 std::size_t hash_even(T* val) {
diff --git a/libcxx/test/std/containers/unord/unord.set/eq.different_hash.pass.cpp b/libcxx/test/std/containers/unord/unord.set/eq.different_hash.pass.cpp
index a763c7fee623a..3cb4815a5bcb1 100644
--- a/libcxx/test/std/containers/unord/unord.set/eq.different_hash.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.set/eq.different_hash.pass.cpp
@@ -36,7 +36,7 @@ std::size_t hash_neg(T val) {
 }
 template <class T>
 std::size_t hash_scale(T val) {
-  return val << 1;
+  return static_cast<std::size_t>(val << 1);
 }
 template <class T>
 std::size_t hash_even(T val) {
@@ -56,11 +56,11 @@ std::size_t hash_neg(T* val) {
   return std::numeric_limits<T>::max() - *val;
 }
 template <class T>
-size_t hash_scale(T* val) {
-  return *val << 1;
+std::size_t hash_scale(T* val) {
+  return static_cast<std::size_t>(*val << 1);
 }
 template <class T>
-size_t hash_even(T* val) {
+std::size_t hash_even(T* val) {
   return *val & 1 ? 1 : 0;
 }
 
diff --git a/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp b/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp
index 01278e9076714..30281a8d922d1 100644
--- a/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp
+++ b/libcxx/test/std/containers/views/mdspan/layout_stride/index_operator.pass.cpp
@@ -53,10 +53,10 @@ constexpr void iterate_stride(M m, const std::array<int, M::extents_type::rank()
   constexpr int r = static_cast<int>(M::extents_type::rank()) - 1 - static_cast<int>(sizeof...(Args));
   if constexpr (-1 == r) {
     ASSERT_NOEXCEPT(m(args...));
-    size_t expected_val = [&]<size_t... Pos>(std::index_sequence<Pos...>) {
+    std::size_t expected_val = static_cast<std::size_t>([&]<std::size_t... Pos>(std::index_sequence<Pos...>) {
       return ((args * strides[Pos]) + ... + 0);
-    }(std::make_index_sequence<M::extents_type::rank()>());
-    assert(expected_val == static_cast<size_t>(m(args...)));
+    }(std::make_index_sequence<M::extents_type::rank()>()));
+    assert(expected_val == static_cast<std::size_t>(m(args...)));
   } else {
     for (typename M::index_type i = 0; i < m.extents().extent(r); i++) {
       iterate_stride(m, strides, i, args...);
@@ -73,7 +73,7 @@ constexpr void test_iteration(std::array<int, E::rank()> strides, Args... args)
 }
 
 constexpr bool test() {
-  constexpr size_t D = std::dynamic_extent;
+  constexpr std::size_t D = std::dynamic_extent;
   test_iteration<std::extents<int>>(std::array<int, 0>{});
   test_iteration<std::extents<unsigned, D>>(std::array<int, 1>{2}, 1);
   test_iteration<std::extents<unsigned, D>>(std::array<int, 1>{3}, 7);
@@ -102,7 +102,7 @@ constexpr bool test() {
 }
 
 constexpr bool test_large() {
-  constexpr size_t D = std::dynamic_extent;
+  constexpr std::size_t D = std::dynamic_extent;
   test_iteration<std::extents<int64_t, D, 8, D, D>>(std::array<int, 4>{2000, 2, 20, 200}, 7, 9, 10);
   test_iteration<std::extents<int64_t, D, 8, 1, D>>(std::array<int, 4>{2000, 20, 20, 200}, 7, 10);
   return true;
diff --git a/libcxx/test/std/ranges/range.utility/range.utility.conv/container.h b/libcxx/test/std/ranges/range.utility/range.utility.conv/container.h
index fafccacd456d5..ca89e3757affc 100644
--- a/libcxx/test/std/ranges/range.utility/range.utility.conv/container.h
+++ b/libcxx/test/std/ranges/range.utility/range.utility.conv/container.h
@@ -38,7 +38,7 @@ struct Container {
 
   constexpr explicit Container(std::ranges::input_range auto&& in)
     requires(Rank >= CtrChoice::DirectCtr)
-      : ctr_choice(CtrChoice::DirectCtr), size_(std::ranges::size(in)) {
+      : ctr_choice(CtrChoice::DirectCtr), size_(static_cast<int>(std::ranges::size(in))) {
     std::ranges::copy(in, begin());
   }
 
@@ -54,7 +54,7 @@ struct Container {
 
   constexpr Container(std::from_range_t, std::ranges::input_range auto&& in)
     requires(Rank >= CtrChoice::FromRangeT)
-      : ctr_choice(CtrChoice::FromRangeT), size_(std::ranges::size(in)) {
+      : ctr_choice(CtrChoice::FromRangeT), size_(static_cast<int>(std::ranges::size(in))) {
     std::ranges::copy(in, begin());
   }
 
@@ -70,7 +70,7 @@ struct Container {
   template <class Iter>
   constexpr Container(Iter b, Iter e)
     requires(Rank >= CtrChoice::BeginEndPair)
-      : ctr_choice(CtrChoice::BeginEndPair), size_(e - b) {
+      : ctr_choice(CtrChoice::BeginEndPair), size_(static_cast<int>(e - b)) {
     std::ranges::copy(b, e, begin());
   }
 
diff --git a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/allocate_shared_for_overwrite.pass.cpp b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/allocate_shared_for_overwrite.pass.cpp
index 27ff3cd563740..e6e063304453a 100644
--- a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/allocate_shared_for_overwrite.pass.cpp
+++ b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/allocate_shared_for_overwrite.pass.cpp
@@ -156,7 +156,7 @@ void testAllocatorOperationsCalled() {
 
 template <class T>
 struct AllocatorWithPattern {
-  constexpr static char pattern = 0xDE;
+  constexpr static char pattern = static_cast<char>(0xDE);
 
   using value_type = T;
 
diff --git a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/make_shared_for_overwrite.pass.cpp b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/make_shared_for_overwrite.pass.cpp
index 21e1786f01588..459b5a708cd4a 100644
--- a/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/make_shared_for_overwrite.pass.cpp
+++ b/libcxx/test/std/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.create/make_shared_for_overwrite.pass.cpp
@@ -56,7 +56,7 @@ static_assert(!HasMakeSharedForOverwrite<Foo[]>);
 static_assert(!HasMakeSharedForOverwrite<int[], std::size_t, int>);
 static_assert(!HasMakeSharedForOverwrite<Foo[], std::size_t, int>);
 
-constexpr char pattern = 0xDE;
+constexpr char pattern = static_cast<char>(0xDE);
 
 void* operator new(std::size_t count) {
   void* ptr = std::malloc(count);
diff --git a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.create/make_unique_for_overwrite.default_init.pass.cpp b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.create/make_unique_for_overwrite.default_init.pass.cpp
index 8011a37be08ec..a1373ac3ac80c 100644
--- a/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.create/make_unique_for_overwrite.default_init.pass.cpp
+++ b/libcxx/test/std/utilities/smartptr/unique.ptr/unique.ptr.create/make_unique_for_overwrite.default_init.pass.cpp
@@ -23,7 +23,7 @@
 #include <cstdlib>
 #include <memory>
 
-constexpr char pattern = 0xDE;
+constexpr char pattern = static_cast<char>(0xDE);
 
 void* operator new(std::size_t count) {
   void* ptr = std::malloc(count);
diff --git a/libcxx/test/support/concat_macros.h b/libcxx/test/support/concat_macros.h
index bc1306fbdb533..7621914e53f02 100644
--- a/libcxx/test/support/concat_macros.h
+++ b/libcxx/test/support/concat_macros.h
@@ -52,14 +52,14 @@ template <class OutIt>
   requires std::output_iterator<OutIt, const char&>
 void test_encode(OutIt& out_it, char16_t value) {
   if (value < 0x80)
-    *out_it++ = value;
+    *out_it++ = static_cast<char>(value);
   else if (value < 0x800) {
-    *out_it++ = 0b11000000 | (value >> 6);
-    *out_it++ = 0b10000000 | (value & 0b00111111);
+    *out_it++ = static_cast<char>(0b11000000 | (value >> 6));
+    *out_it++ = static_cast<char>(0b10000000 | (value & 0b00111111));
   } else {
-    *out_it++ = 0b11100000 | (value >> 12);
-    *out_it++ = 0b10000000 | ((value) >> 6 & 0b00111111);
-    *out_it++ = 0b10000000 | (value & 0b00111111);
+    *out_it++ = static_cast<char>(0b11100000 | (value >> 12));
+    *out_it++ = static_cast<char>(0b10000000 | ((value) >> 6 & 0b00111111));
+    *out_it++ = static_cast<char>(0b10000000 | (value & 0b00111111));
   }
 }
 
@@ -69,10 +69,10 @@ void test_encode(OutIt& out_it, char32_t value) {
   if ((value & 0xffff0000) == 0)
     test_encode(out_it, static_cast<char16_t>(value));
   else {
-    *out_it++ = 0b11100000 | (value >> 18);
-    *out_it++ = 0b10000000 | ((value) >> 12 & 0b00111111);
-    *out_it++ = 0b10000000 | ((value) >> 6 & 0b00111111);
-    *out_it++ = 0b10000000 | (value & 0b00111111);
+    *out_it++ = static_cast<char>(0b11100000 | (value >> 18));
+    *out_it++ = static_cast<char>(0b10000000 | ((value) >> 12 & 0b00111111));
+    *out_it++ = static_cast<char>(0b10000000 | ((value) >> 6 & 0b00111111));
+    *out_it++ = static_cast<char>(0b10000000 | (value & 0b00111111));
   }
 }