diff --git a/test/module-test.cc b/test/module-test.cc
index d8a120d0b566d..75e53138a75e1 100644
--- a/test/module-test.cc
+++ b/test/module-test.cc
@@ -9,6 +9,16 @@
 // All Rights Reserved
 // {fmt} module.
 
+#include <string>
+#include <string_view>
+#include <chrono>
+#include <locale>
+#include <iterator>
+#include <memory>
+#include <exception>
+#include <system_error>
+#include <ostream>
+
 import fmt;
 
 // check for macros leaking from BMI
@@ -19,11 +29,12 @@ static bool macro_leaked =
   false;
 #endif
 
-#include "gtest/gtest.h"
+#include "gtest-extra.h"
 
 // an implicitly exported namespace must be visible [module.interface]/2.2
 TEST(module_test, namespace) {
   using namespace fmt;
+  using namespace fmt::literals;
   ASSERT_TRUE(true);
 }
 
@@ -34,8 +45,8 @@ bool oops_detail_namespace_is_visible;
 namespace fmt {
 bool namespace_detail_invisible() {
 #if defined(FMT_HIDE_MODULE_BUGS) && \
-  defined(_MSC_FULL_VER) && _MSC_FULL_VER <= 192930036
-  // bug in msvc 16.10-pre4:
+  defined(_MSC_FULL_VER) && _MSC_FULL_VER <= 192930129
+  // bug in msvc up to 16.11-pre1:
   // the namespace is visible even when it is neither
   // implicitly nor explicitly exported
   return true;
@@ -55,11 +66,495 @@ TEST(module_test, detail_namespace) {
 // macros must not be imported from a *named* module  [cpp.import]/5.1
 TEST(module_test, macros) {
 #if defined(FMT_HIDE_MODULE_BUGS) && \
-  defined(_MSC_FULL_VER) && _MSC_FULL_VER <= 192930036
-// bug in msvc 16.10-pre4:
+  defined(_MSC_FULL_VER) && _MSC_FULL_VER <= 192930129
+// bug in msvc up to 16.11-pre1:
 // include-guard macros leak from BMI
 // and even worse: they cannot be #undef-ined
   macro_leaked = false;
 #endif
   EXPECT_FALSE(macro_leaked);
 }
+
+// The following is less about functional testing (that's done elsewhere)
+// but rather visibility of all client-facing overloads, reachability of
+// non-exported entities, name lookup and overload resolution within
+// template instantitions.
+// Excercise all exported entities of the API at least once.
+// Instantiate as many code paths as possible.
+
+TEST(module_test, to_string) {
+  EXPECT_EQ("42", fmt::to_string(42));
+  EXPECT_EQ("42", fmt::to_string(42.0));
+}
+
+TEST(module_test, format) {
+  EXPECT_EQ("42", fmt::format("{:}", 42));
+  EXPECT_EQ("-42", fmt::format("{0}", -42.0));
+}
+
+TEST(module_test, format_to) {
+  std::string s;
+  fmt::format_to(std::back_inserter(s), "{}", 42);
+  EXPECT_EQ("42", s);
+
+  char buffer[4] = {0};
+  fmt::format_to(buffer, "{}", 42);
+  EXPECT_EQ("42", std::string_view(buffer));
+
+  fmt::memory_buffer mb;
+  fmt::format_to(mb, "{}", 42);
+  EXPECT_EQ("42", std::string_view(buffer));
+}
+
+TEST(module_test, formatted_size) {
+  EXPECT_EQ(2u, fmt::formatted_size("{}", 42));
+}
+
+TEST(module_test, format_to_n) {
+  std::string s;
+  auto result = fmt::format_to_n(std::back_inserter(s), 1, "{}", 42);
+  EXPECT_EQ(2u, result.size);
+  char buffer[4] = {0};
+  fmt::format_to_n(buffer, 3, "{}", 12345);
+}
+
+TEST(module_test, format_args) {
+  auto no_args = fmt::format_args();
+  EXPECT_FALSE(no_args.get(1));
+
+  using ctx = fmt::format_context;
+  fmt::basic_format_args<ctx> args = fmt::make_format_args<ctx>(42);
+  EXPECT_TRUE(args.max_size() > 0);
+  auto arg0 = args.get(0);
+  EXPECT_TRUE(arg0);
+  decltype(arg0) arg_none;
+  EXPECT_FALSE(arg_none);
+  EXPECT_TRUE(arg0.type() != arg_none.type());
+}
+
+TEST(module_test, checked_format_args) {
+  fmt::basic_format_args<fmt::format_context> args =
+    fmt::make_args_checked<int>("{}", 42);
+  EXPECT_TRUE(args.get(0));
+}
+
+TEST(module_test, dynamic_format_args) {
+  using ctx = fmt::format_context;
+  fmt::dynamic_format_arg_store<ctx> dyn_store;
+  dyn_store.push_back(fmt::arg("a42", 42));
+  fmt::basic_format_args<ctx> args = dyn_store;
+  EXPECT_FALSE(args.get(3));
+  EXPECT_TRUE(args.get(fmt::string_view("a42")));
+}
+
+TEST(module_test, vformat) {
+  using ctx = fmt::format_context;
+  EXPECT_EQ("42", fmt::vformat("{}", fmt::make_format_args<ctx>(42)));
+}
+
+TEST(module_test, vformat_to) {
+  auto store = fmt::make_format_args<fmt::format_context>(42);
+  std::string s;
+  fmt::vformat_to(std::back_inserter(s), "{}", store);
+  EXPECT_EQ("42", s);
+
+  char buffer[4] = {0};
+  fmt::vformat_to(buffer, "{}", store);
+  EXPECT_EQ("42", std::string_view(buffer));
+}
+
+TEST(module_test, vformat_to_n) {
+  auto store = fmt::make_format_args<fmt::format_context>(12345);
+  std::string s;
+  auto result = fmt::vformat_to_n(std::back_inserter(s), 1, "{}", store);
+  char buffer[4] = {0};
+  fmt::vformat_to_n(buffer, 3, "{}", store);
+}
+
+TEST(module_test, print) {
+  EXPECT_WRITE(stdout, fmt::print("{}µ", 42), "42µ");
+  EXPECT_WRITE(stderr, fmt::print(stderr, "{}µ", 4.2), "4.2µ");
+}
+
+TEST(module_test, vprint) {
+  using ctx = fmt::format_context;
+  EXPECT_WRITE(stdout,
+    fmt::vprint("{}", fmt::make_format_args<ctx>(42)), "42");
+  EXPECT_WRITE(stderr,
+    fmt::vprint(stderr, "{}", fmt::make_format_args<ctx>(4.2)), "4.2");
+}
+
+TEST(module_test, named_args) {
+  EXPECT_EQ("42", fmt::format("{answer}", fmt::arg("answer", 42)));
+}
+
+TEST(module_test, literals) {
+  using namespace fmt::literals;
+  EXPECT_EQ("42", fmt::format("{answer}", "answer"_a = 42));
+  EXPECT_EQ("42", "{}"_format(42));
+}
+
+TEST(module_test, locale) {
+  auto store = fmt::make_format_args<fmt::format_context>(4.2);
+  const auto de = std::locale("de_DE");
+  EXPECT_EQ("4,2", fmt::format(de, "{:L}", 4.2));
+  EXPECT_EQ("4,2", fmt::vformat(de, "{:L}", store));
+  std::string s;
+  fmt::vformat_to(de, std::back_inserter(s), "{:L}", store);
+  EXPECT_EQ("4,2", s);
+
+  const auto previous = std::locale::global(std::locale("ru_RU"));
+  EXPECT_EQ("4,2", fmt::format("{:L}", 4.2));
+  std::locale::global(previous);
+}
+
+TEST(module_test, string_view) {
+  fmt::string_view nsv("fmt");
+  EXPECT_EQ("fmt", nsv);
+  EXPECT_TRUE(fmt::string_view("fmt") == nsv);
+
+  fmt::wstring_view wsv(L"fmt");
+  EXPECT_EQ(L"fmt", wsv);
+  EXPECT_TRUE(fmt::wstring_view(L"fmt") == wsv);
+}
+
+TEST(module_test, memory_buffer) {
+  fmt::basic_memory_buffer<char, fmt::inline_buffer_size> buffer;
+  fmt::format_to(buffer, "{}", "42");
+  EXPECT_EQ("42", to_string(buffer));
+  fmt::memory_buffer nbuffer(std::move(buffer));
+  EXPECT_EQ("42", to_string(nbuffer));
+  buffer = std::move(nbuffer);
+  EXPECT_EQ("42", to_string(buffer));
+  nbuffer.clear();
+  EXPECT_EQ(0u, to_string(nbuffer).size());
+
+  fmt::wmemory_buffer wbuffer;
+  EXPECT_EQ(0u, to_string(wbuffer).size());
+}
+
+TEST(module_test, is_char) {
+  EXPECT_TRUE(fmt::is_char<char>());
+  EXPECT_TRUE(fmt::is_char<wchar_t>());
+  EXPECT_TRUE(fmt::is_char<char8_t>());
+  EXPECT_TRUE(fmt::is_char<char16_t>());
+  EXPECT_TRUE(fmt::is_char<char32_t>());
+  EXPECT_FALSE(fmt::is_char<signed char>());
+}
+
+TEST(module_test, ptr) {
+  auto p = (int*)42;
+  EXPECT_EQ("0x2a", fmt::to_string(fmt::ptr(p)));
+  std::unique_ptr<int> up(p);
+  EXPECT_EQ("0x2a", fmt::to_string(fmt::ptr(up)));
+  up.release();
+  auto sp = std::make_shared<int>(0);
+  p = sp.get();
+  EXPECT_EQ(fmt::to_string(fmt::ptr(p)), fmt::to_string(fmt::ptr(sp)));
+}
+
+TEST(module_test, errors) {
+  auto store = fmt::make_format_args<fmt::format_context>(42);
+  EXPECT_THROW(throw fmt::format_error("oops"), std::exception);
+  EXPECT_THROW(throw fmt::vsystem_error(0, "{}", store),
+               std::system_error);
+  EXPECT_THROW(throw fmt::system_error(0, "{}", 42),
+               std::system_error);
+
+  fmt::memory_buffer buffer;
+  fmt::format_system_error(buffer, 0, "oops");
+  EXPECT_TRUE(to_string(buffer).size() > 0);
+  EXPECT_WRITE(stderr, fmt::report_system_error(0, "oops"),
+               to_string(buffer));
+}
+
+TEST(module_test, format_int) {
+  fmt::format_int sanswer(42);
+  EXPECT_EQ("42", fmt::string_view(sanswer.data(), sanswer.size()));
+  fmt::format_int uanswer(42u);
+  EXPECT_EQ("42", fmt::string_view(uanswer.data(), uanswer.size()));
+}
+
+struct test_formatter : fmt::formatter<char> {
+  bool check() { return true; }
+};
+
+struct test_dynamic_formatter : fmt::dynamic_formatter<> {
+  bool check() { return true; }
+};
+
+TEST(module_test, formatter) {
+  EXPECT_TRUE(test_formatter{}.check());
+  EXPECT_TRUE(test_dynamic_formatter{}.check());
+}
+
+TEST(module_test, join) {
+  int arr[3] = {1, 2, 3};
+  std::vector<double> vec{1.0, 2.0, 3.0};
+  EXPECT_EQ("1, 2, 3", to_string(fmt::join(arr + 0, arr + 3, ", ")));
+  EXPECT_EQ("1, 2, 3", to_string(fmt::join(arr, ", ")));
+  EXPECT_EQ("1, 2, 3", to_string(fmt::join(vec.begin(), vec.end(), ", ")));
+  EXPECT_EQ("1, 2, 3", to_string(fmt::join(vec, ", ")));
+}
+
+TEST(module_test, time) {
+  auto time_now = std::time(nullptr);
+  EXPECT_TRUE(fmt::localtime(time_now).tm_year > 120);
+  EXPECT_TRUE(fmt::gmtime(time_now).tm_year > 120);
+  auto chrono_now = std::chrono::system_clock::now();
+  EXPECT_TRUE(fmt::localtime(chrono_now).tm_year > 120);
+  EXPECT_TRUE(fmt::gmtime(chrono_now).tm_year > 120);
+}
+
+TEST(module_test, time_point) {
+  auto now = std::chrono::system_clock::now();
+  std::string_view past("2021-05-20 10:30:15");
+  EXPECT_TRUE(past < fmt::format("{:%Y-%m-%d %H:%M:%S}", now));
+}
+
+TEST(module_test, time_duration) {
+  EXPECT_EQ("42s", fmt::format("{}", std::chrono::seconds{42}));
+  using us = std::chrono::duration<double, std::micro>;
+  EXPECT_EQ("4.2µs", fmt::format("{:3.1}", us{4.234}));
+  const auto de = std::locale("de_DE");
+// localized float formatting is not yet implemented
+// EXPECT_EQ("4,23µs", fmt::format(de, "{:3.2L}", us{4.234}));
+  EXPECT_EQ("4.23µs", fmt::format(de, "{:3.2L}", us{4.234}));
+}
+
+TEST(module_test, to_string_view) {
+  using fmt::to_string_view;
+  fmt::string_view nsv{to_string_view("42")};
+  EXPECT_EQ("42", nsv);
+  fmt::wstring_view wsv{to_string_view(L"42")};
+  EXPECT_EQ(L"42", wsv);
+}
+
+TEST(module_test, printf) {
+  EXPECT_WRITE(stdout, fmt::printf("%f", 42.123456), "42.123456");
+  EXPECT_WRITE(stdout, fmt::printf("%d", 42), "42");
+}
+
+TEST(module_test, fprintf) {
+  EXPECT_WRITE(stderr, fmt::fprintf(stderr, "%d", 42), "42");
+  std::ostringstream os;
+  fmt::fprintf(os, "%s", "bla");
+  EXPECT_EQ("bla", os.str());
+}
+
+TEST(module_test, sprintf) {
+  EXPECT_EQ("42", fmt::sprintf("%d", 42));
+}
+
+TEST(module_test, vprintf) {
+  EXPECT_WRITE(stdout, fmt::vprintf("%d", fmt::make_printf_args(42)), "42");
+}
+
+TEST(module_test, vfprintf) {
+  auto args =  fmt::make_printf_args(42);
+  EXPECT_WRITE(stderr, fmt::vfprintf(stderr, "%d", args), "42");
+  std::ostringstream os;
+  fmt::vfprintf(os, "%d", args);
+  EXPECT_EQ("42", os.str());
+}
+
+TEST(module_test, vsprintf) {
+  EXPECT_EQ("42", fmt::vsprintf("%d", fmt::make_printf_args(42)));
+}
+
+TEST(module_test, color) {
+  auto fg_check = fg(fmt::rgb(255, 200, 30));
+  auto bg_check = bg(fmt::color::dark_slate_gray) | fmt::emphasis::italic;
+  auto emphasis_check = fmt::emphasis::underline | fmt::emphasis::bold;
+  EXPECT_EQ("\x1B[30m42\x1B[0m",
+    fmt::format(fg(fmt::terminal_color::black), "{}", 42));
+}
+
+struct custom_context {
+  using char_type = char;
+  using parse_context_type = fmt::format_parse_context;
+
+  bool called = false;
+
+  template <typename T> struct formatter_type {
+    auto parse(fmt::format_parse_context& ctx) -> decltype(ctx.begin()) {
+      return ctx.begin();
+    }
+
+    const char* format(const T&, custom_context& ctx) {
+      ctx.called = true;
+      return nullptr;
+    }
+  };
+
+  void advance_to(const char*) {}
+};
+
+struct test_struct {};
+
+namespace fmt {
+template <typename Char> struct formatter<test_struct, Char> {
+  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  auto format(test_struct, format_context& ctx) -> decltype(ctx.out()) {
+    auto test = string_view("test");
+    return std::copy_n(test.data(), test.size(), ctx.out());
+  }
+};
+}
+
+TEST(arg_test, custom_context) {
+  auto ctx = custom_context();
+  auto parse_ctx = fmt::format_parse_context("");
+  fmt::basic_format_arg<custom_context> custom_arg;
+  EXPECT_TRUE(!custom_arg);
+
+  auto test = test_struct();
+  auto store = fmt::dynamic_format_arg_store<custom_context>();
+  store.push_back(test);
+}
+
+struct enabled_formatter {};
+struct disabled_formatter {};
+struct disabled_formatter_convertible {
+  operator int() const { return 42; }
+};
+
+namespace fmt {
+  template <> struct formatter<enabled_formatter> {
+  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+  auto format(enabled_formatter, format_context& ctx) -> decltype(ctx.out()) {
+    return ctx.out();
+  }
+};
+}
+
+TEST(core_test, has_formatter) {
+  using fmt::has_formatter;
+  using context = fmt::format_context;
+  static_assert(has_formatter<enabled_formatter, context>::value, "");
+  static_assert(!has_formatter<disabled_formatter, context>::value, "");
+  static_assert(!has_formatter<disabled_formatter_convertible, context>::value,
+                "");
+}
+
+TEST(core_test, is_formattable) {
+  static_assert(fmt::is_formattable<enabled_formatter>::value, "");
+  static_assert(!fmt::is_formattable<disabled_formatter>::value, "");
+  static_assert(fmt::is_formattable<disabled_formatter_convertible>::value, "");
+}
+
+struct convertible_to_int {
+  operator int() const { return 42; }
+};
+
+struct convertible_to_c_string {
+  operator const char*() const { return "foo"; }
+};
+
+namespace fmt {
+template <> struct formatter<convertible_to_int> {
+  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+  auto format(convertible_to_int, format_context& ctx) -> decltype(ctx.out()) {
+    return std::copy_n("foo", 3, ctx.out());
+  }
+};
+
+template <> struct formatter<convertible_to_c_string> {
+  constexpr auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+  auto format(convertible_to_c_string, format_context& ctx)
+      -> decltype(ctx.out()) {
+    return std::copy_n("bar", 3, ctx.out());
+  }
+};
+}
+
+TEST(core_test, formatter_overrides_implicit_conversion) {
+  EXPECT_EQ(fmt::format("{}", convertible_to_int()), "foo");
+  EXPECT_EQ(fmt::format("{}", convertible_to_c_string()), "bar");
+}
+
+// Test that check is not found by ADL.
+template <typename T> void check(T);
+TEST(core_test, adl_check) {
+  EXPECT_EQ(fmt::format("{}", test_struct()), "test");
+}
+
+struct implicitly_convertible_to_string {
+  operator std::string() const { return "foo"; }
+};
+
+struct implicitly_convertible_to_string_view {
+  operator fmt::string_view() const { return "foo"; }
+};
+
+TEST(core_test, format_implicitly_convertible_to_string_view) {
+  EXPECT_EQ("foo", fmt::format("{}", implicitly_convertible_to_string_view()));
+}
+
+struct explicitly_convertible_to_string_view {
+  explicit operator fmt::string_view() const { return "foo"; }
+};
+
+TEST(core_test, format_explicitly_convertible_to_string_view) {
+  EXPECT_EQ("foo", fmt::format("{}", explicitly_convertible_to_string_view()));
+}
+
+struct explicitly_convertible_to_std_string_view {
+  explicit operator std::string_view() const { return "foo"; }
+};
+
+TEST(core_test, format_explicitly_convertible_to_std_string_view) {
+  EXPECT_EQ("foo",
+            fmt::format("{}", explicitly_convertible_to_std_string_view()));
+}
+
+struct convertible_to_long_long {
+  operator long long() const { return 1LL << 32; }
+};
+
+TEST(format_test, format_convertible_to_long_long) {
+  EXPECT_EQ("100000000", fmt::format("{:x}", convertible_to_long_long()));
+}
+
+struct disabled_rvalue_conversion {
+  operator const char*() const& { return "foo"; }
+  operator const char*() & { return "foo"; }
+  operator const char*() const&& = delete;
+  operator const char*() && = delete;
+};
+
+TEST(core_test, disabled_rvalue_conversion) {
+  EXPECT_EQ("foo", fmt::format("{}", disabled_rvalue_conversion()));
+}
+
+namespace adl_test {
+template <typename... T> void make_format_args(const T&...) = delete;
+
+struct string : std::string {};
+}  // namespace adl_test
+
+template <typename T> constexpr T const_check(T value) { return value; }
+
+// Test that formatting functions compile when make_format_args is found by ADL.
+TEST(core_test, adl) {
+  // Only check compilation and don't run the code to avoid polluting the output
+  // and since the output is tested elsewhere.
+  if (::const_check(true)) return;
+  auto s = adl_test::string();
+  char buf[10];
+  fmt::format("{}", s);
+  fmt::format_to(buf, "{}", s);
+  fmt::format_to_n(buf, 10, "{}", s);
+  fmt::formatted_size("{}", s);
+  fmt::print("{}", s);
+  fmt::print(stdout, "{}", s);
+}