diff --git a/stl/inc/format b/stl/inc/format
index 16466b6980d..f968858c563 100644
--- a/stl/inc/format
+++ b/stl/inc/format
@@ -305,7 +305,8 @@ constexpr const _CharT* _Parse_format_specs(const _CharT* _Begin, const _CharT*
 template <class _Ty, class _CharT = char>
 struct formatter;
 
-// TODO: test coverage
+inline void _You_see_this_error_because_arg_id_is_out_of_range() noexcept {}
+
 template <class _CharT>
 class basic_format_parse_context {
 public:
@@ -313,15 +314,6 @@ public:
     using const_iterator = typename basic_string_view<_CharT>::const_iterator;
     using iterator       = const_iterator;
 
-private:
-    basic_string_view<_CharT> _Format_string;
-    size_t _Num_args;
-    // The standard says this is size_t, however we use ptrdiff_t to save some space
-    // by not having to store the indexing mode. Below is a more detailed explanation
-    // of how this works.
-    ptrdiff_t _Next_arg_id = 0;
-
-public:
     constexpr explicit basic_format_parse_context(basic_string_view<_CharT> _Fmt, size_t _Num_args_ = 0) noexcept
         : _Format_string(_Fmt), _Num_args(_Num_args_) {}
     basic_format_parse_context(const basic_format_parse_context&) = delete;
@@ -333,8 +325,10 @@ public:
     _NODISCARD constexpr const_iterator end() const noexcept {
         return _Format_string.end();
     }
-    constexpr void advance_to(const_iterator _It) {
-        _Format_string.remove_prefix(_It - begin());
+    constexpr void advance_to(const const_iterator _It) {
+        _Adl_verify_range(_It, _Format_string.end());
+        const auto _Diff = static_cast<size_t>(_It._Unwrapped() - _Format_string._Unchecked_begin());
+        _Format_string.remove_prefix(_Diff);
     }
 
     // While the standard presents an exposition only enum value for
@@ -343,18 +337,33 @@ public:
     // _Next_arg_id > 0 means automatic
     // _Next_arg_id == -1 means manual
     constexpr size_t next_arg_id() {
-        if (_Next_arg_id >= 0) {
-            return _Next_arg_id++;
+        if (_Next_arg_id == -1) {
+            throw format_error("Can not switch from manual to automatic indexing");
         }
-        throw format_error("Can not switch from manual to automatic indexing");
+
+        return static_cast<size_t>(_Next_arg_id++);
     }
-    constexpr void check_arg_id(size_t _Id) {
-        (void) _Id;
+
+    constexpr void check_arg_id(const size_t _Id) {
+        if (_STD is_constant_evaluated()) {
+            if (_Id >= _Num_args) {
+                _You_see_this_error_because_arg_id_is_out_of_range();
+            }
+        }
+
         if (_Next_arg_id > 0) {
             throw format_error("Can not switch from automatic to manual indexing");
         }
         _Next_arg_id = -1;
     }
+
+private:
+    basic_string_view<_CharT> _Format_string;
+    size_t _Num_args;
+    // The standard says this is size_t, however we use ptrdiff_t to save some space
+    // by not having to store the indexing mode. Above is a more detailed explanation
+    // of how this works.
+    ptrdiff_t _Next_arg_id = 0;
 };
 
 // TODO: test coverage
diff --git a/tests/std/test.lst b/tests/std/test.lst
index de1a48a5e19..7d5f3a8123d 100644
--- a/tests/std/test.lst
+++ b/tests/std/test.lst
@@ -243,6 +243,7 @@ tests\P0595R2_is_constant_evaluated
 tests\P0607R0_inline_variables
 tests\P0616R0_using_move_in_numeric
 tests\P0631R8_numbers_math_constants
+tests\P0645R10_text_formatting_death
 tests\P0645R10_text_formatting_parse_contexts
 tests\P0645R10_text_formatting_parsing
 tests\P0660R10_jthread_and_cv_any
diff --git a/tests/std/tests/P0645R10_text_formatting_death/env.lst b/tests/std/tests/P0645R10_text_formatting_death/env.lst
new file mode 100644
index 00000000000..22f1f0230a4
--- /dev/null
+++ b/tests/std/tests/P0645R10_text_formatting_death/env.lst
@@ -0,0 +1,4 @@
+# Copyright (c) Microsoft Corporation.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+RUNALL_INCLUDE ..\strict_winsdk_concepts_matrix.lst
diff --git a/tests/std/tests/P0645R10_text_formatting_death/test.cpp b/tests/std/tests/P0645R10_text_formatting_death/test.cpp
new file mode 100644
index 00000000000..86e74da6037
--- /dev/null
+++ b/tests/std/tests/P0645R10_text_formatting_death/test.cpp
@@ -0,0 +1,30 @@
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#define _CONTAINER_DEBUG_LEVEL 1
+
+#include <assert.h>
+#include <format>
+#include <string_view>
+
+#include <test_death.hpp>
+using namespace std;
+
+void test_case_advance_no_range() {
+    const auto format_string       = "First {} and second {} and third {}"sv;
+    const auto other_format_string = "something"sv;
+    basic_format_parse_context context{format_string};
+    context.advance_to(other_format_string.begin());
+}
+
+int main(int argc, char* argv[]) {
+    std_testing::death_test_executive exec;
+
+#if _ITERATOR_DEBUG_LEVEL != 0
+    exec.add_death_tests({
+        test_case_advance_no_range,
+    });
+#endif // _ITERATOR_DEBUG_LEVEL != 0
+
+    return exec.run(argc, argv);
+}
diff --git a/tests/std/tests/P0645R10_text_formatting_parse_contexts/env.lst b/tests/std/tests/P0645R10_text_formatting_parse_contexts/env.lst
index f3ccc8613c6..22f1f0230a4 100644
--- a/tests/std/tests/P0645R10_text_formatting_parse_contexts/env.lst
+++ b/tests/std/tests/P0645R10_text_formatting_parse_contexts/env.lst
@@ -1,4 +1,4 @@
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-RUNALL_INCLUDE ..\concepts_matrix.lst
+RUNALL_INCLUDE ..\strict_winsdk_concepts_matrix.lst
diff --git a/tests/std/tests/P0645R10_text_formatting_parse_contexts/test.cpp b/tests/std/tests/P0645R10_text_formatting_parse_contexts/test.cpp
index 7a3f5c0dad2..606f08b51f4 100644
--- a/tests/std/tests/P0645R10_text_formatting_parse_contexts/test.cpp
+++ b/tests/std/tests/P0645R10_text_formatting_parse_contexts/test.cpp
@@ -2,11 +2,108 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 #include <assert.h>
+#include <concepts>
+#include <cstddef>
 #include <format>
+#include <memory>
 #include <string_view>
+#include <type_traits>
 
-// TODO: fill in tests
+using namespace std;
+
+template <class CharType>
+constexpr auto get_input() {
+    if constexpr (same_as<CharType, char>) {
+        return "First {} and second {} and third {}"sv;
+    } else {
+        return L"First {} and second {} and third {}"sv;
+    }
+}
+
+template <class CharType>
+constexpr bool ensure_is_constant_expression(const bool should_be_constant_expression) {
+    basic_format_parse_context<CharType> context{get_input<CharType>(), 1};
+    if (should_be_constant_expression) {
+        context.check_arg_id(0);
+    } else {
+        context.check_arg_id(1);
+    }
+
+    return is_constant_evaluated();
+}
+
+const bool check_arg_id_is_constexpr_char   = ensure_is_constant_expression<char>(true);
+const bool check_arg_id_not_constexpr_char  = !ensure_is_constant_expression<char>(false);
+const bool check_arg_id_is_constexpr_wchar  = ensure_is_constant_expression<wchar_t>(true);
+const bool check_arg_id_not_constexpr_wchar = !ensure_is_constant_expression<wchar_t>(false);
+
+template <class CharType>
+constexpr bool test_basic_format_parse_context() {
+    static_assert(!is_copy_constructible_v<basic_format_parse_context<CharType>>);
+    static_assert(!is_copy_assignable_v<basic_format_parse_context<CharType>>);
+
+    const auto format_string = get_input<CharType>();
+    { // iterator interface
+        basic_format_parse_context<CharType> context{format_string};
+        const same_as<typename basic_string_view<CharType>::const_iterator> auto b = context.begin();
+        assert(b == format_string.begin());
+        static_assert(noexcept(context.begin()));
+
+        const same_as<typename basic_string_view<CharType>::const_iterator> auto e = context.end();
+        assert(e == format_string.end());
+        static_assert(noexcept(context.end()));
+
+        const auto new_position = format_string.begin() + 5;
+        context.advance_to(new_position);
+        assert(to_address(context.begin()) == to_address(new_position));
+        assert(to_address(context.end()) == to_address(e));
+    }
+
+    { // arg_id
+        basic_format_parse_context<CharType> context{format_string};
+        const same_as<size_t> auto first_arg_id = context.next_arg_id();
+        assert(first_arg_id == 0);
+
+        const same_as<size_t> auto second_arg_id = context.next_arg_id();
+        assert(second_arg_id == 1);
+
+        if (!is_constant_evaluated()) {
+            try {
+                context.check_arg_id(0);
+            } catch (const format_error& e) {
+                assert(e.what() == "Can not switch from automatic to manual indexing"sv);
+            }
+        }
+    }
+
+    { // check_arg_id
+        basic_format_parse_context<CharType> context{format_string, 3};
+        context.check_arg_id(0);
+        context.check_arg_id(1);
+        context.check_arg_id(2); // intentional duplicates to check whether this is ok to call multiple times
+        context.check_arg_id(1);
+        context.check_arg_id(0);
+
+        if (!is_constant_evaluated()) {
+            try {
+                context.next_arg_id();
+            } catch (const format_error& e) {
+                assert(e.what() == "Can not switch from manual to automatic indexing"sv);
+            }
+        }
+    }
+
+    return true;
+}
 
 int main() {
-    return 0;
+    test_basic_format_parse_context<char>();
+    test_basic_format_parse_context<wchar_t>();
+    static_assert(test_basic_format_parse_context<char>());
+    static_assert(test_basic_format_parse_context<wchar_t>());
+
+    assert(check_arg_id_is_constexpr_char);
+    assert(check_arg_id_not_constexpr_char);
+    assert(check_arg_id_is_constexpr_wchar);
+    assert(check_arg_id_not_constexpr_wchar);
 }