diff --git a/tests/algorithm_tests.cpp b/tests/algorithm_tests.cpp
index e42a99d..c88a120 100644
--- a/tests/algorithm_tests.cpp
+++ b/tests/algorithm_tests.cpp
@@ -24,21 +24,23 @@
 // disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
-#include <gtest/gtest.h>
+#endif // __clang__
 
+#include <gtest/gtest.h>
 #include <gsl/gsl_algorithm> // for copy
 #include <gsl/span>          // for span
 #include <array>   // for array
 #include <cstddef> // for size_t
 
-namespace{
-static const char *deathstring("Expected Death");
+namespace
+{
+    static constexpr char deathstring[] = "Expected Death";
 }
 
 namespace gsl
@@ -244,4 +246,4 @@ TEST(algorithm_tests, small_destination_span)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/assertion_tests.cpp b/tests/assertion_tests.cpp
index 0e4dd34..a42c209 100644
--- a/tests/assertion_tests.cpp
+++ b/tests/assertion_tests.cpp
@@ -24,12 +24,13 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 #include <gsl/gsl_assert> // for fail_fast (ptr only), Ensures, Expects
@@ -38,6 +39,8 @@ using namespace gsl;
 
 namespace
 {
+static constexpr char deathstring[] = "Expected Death";
+
 int f(int i)
 {
     Expects(i > 0 && i < 10);
@@ -50,8 +53,6 @@ int g(int i)
     Ensures(i > 0 && i < 10);
     return i;
 }
-
-static const char *deathstring("Expected Death");
 } // namespace
 
 TEST(assertion_tests, expects)
@@ -79,4 +80,4 @@ TEST(assertion_tests, ensures)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/at_tests.cpp b/tests/at_tests.cpp
index 98f261a..b43d06c 100644
--- a/tests/at_tests.cpp
+++ b/tests/at_tests.cpp
@@ -24,12 +24,13 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -40,8 +41,9 @@
 #include <initializer_list> // for initializer_list
 #include <vector>           // for vector
 
-namespace{
-static const char *deathstring("Expected Death");
+namespace
+{
+    static constexpr char deathstring[] = "Expected Death";
 }
 
 TEST(at_tests, static_array)
@@ -152,4 +154,4 @@ static_assert(test_constexpr(), "FAIL");
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/bounds_tests.cpp b/tests/bounds_tests.cpp
index 5e73042..629e5d1 100644
--- a/tests/bounds_tests.cpp
+++ b/tests/bounds_tests.cpp
@@ -27,12 +27,13 @@
 
 //disable warnings from gtest
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -40,10 +41,6 @@
 
 #include <cstddef> // for ptrdiff_t, size_t
 
-namespace gsl {
-struct fail_fast;
-}  // namespace gsl
-
 using namespace std;
 using namespace gsl;
 
@@ -127,4 +124,4 @@ copy(src_span_static, dst_span_static);
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
index 36e10b0..bf22556 100644
--- a/tests/byte_tests.cpp
+++ b/tests/byte_tests.cpp
@@ -17,19 +17,20 @@
 #ifdef _MSC_VER
 // blanket turn off warnings from CppCoreCheck from catch
 // so people aren't annoyed by them when running the tool.
-#pragma warning(disable : 26440 26426) // from catch
-#endif
+#pragma warning(disable : 26440 26426)
+#endif // _MSC_VER
 
 #if __clang__ || __GNUC__
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -147,4 +148,4 @@ copy(src_span_static, dst_span_static);
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/multi_span_tests.cpp b/tests/multi_span_tests.cpp
index a4fdc56..891bee3 100644
--- a/tests/multi_span_tests.cpp
+++ b/tests/multi_span_tests.cpp
@@ -28,13 +28,13 @@
 
 //disable warnings from gtest
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -61,6 +61,7 @@ using namespace gsl;
 
 namespace
 {
+static constexpr char deathstring[] = "Expected Death";
 struct BaseClass
 {
 };
@@ -139,7 +140,6 @@ void fn(const Bounds&)
     static_assert(Bounds::static_size == 60, "static bounds is wrong size");
 }
 
-static const char *deathstring("Expected Death");
 } // namespace
 
 TEST(multi_span_test, default_constructor)
@@ -1886,4 +1886,4 @@ copy(src_span_static, dst_span_static);
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/notnull_tests.cpp b/tests/notnull_tests.cpp
index b1ac4d4..47f5ac2 100644
--- a/tests/notnull_tests.cpp
+++ b/tests/notnull_tests.cpp
@@ -27,12 +27,13 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -52,9 +53,9 @@ struct fail_fast;
 
 using namespace gsl;
 
-namespace{
-static const char *deathstring("Expected Death");
-}
+namespace
+{
+static constexpr char deathstring[] = "Expected Death";
 
 struct MyBase
 {
@@ -148,7 +149,7 @@ GSL_SUPPRESS(f.4) // NO-FORMAT: attribute
 bool helper_const(not_null<const int*> p) { return *p == 12; }
 
 int* return_pointer() { return nullptr; }
-const int* return_pointer_const() { return nullptr; }
+} //namespace
 
 TEST(notnull_tests, TestNotNullConstructors)
 {
@@ -564,4 +565,4 @@ static_assert(std::is_nothrow_move_constructible<not_null<void*>>::value,
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/owner_tests.cpp b/tests/owner_tests.cpp
index 2427803..6442033 100644
--- a/tests/owner_tests.cpp
+++ b/tests/owner_tests.cpp
@@ -25,12 +25,13 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -62,4 +63,4 @@ TEST(owner_tests, check_pointer_constraint)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/span_tests.cpp b/tests/span_tests.cpp
index 9336812..f619d48 100644
--- a/tests/span_tests.cpp
+++ b/tests/span_tests.cpp
@@ -26,17 +26,19 @@
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
 #pragma GCC diagnostic ignored "-Wunused-variable"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
+
+#include <gtest/gtest.h>
 
 #include <gsl/gsl_byte> // for byte
 #include <gsl/gsl_util> // for narrow_cast, at
 #include <gsl/span>     // for span, span_iterator, operator==, operator!=
-#include <gtest/gtest.h>
 
 #include <array>       // for array
 #include <iostream>    // for ptrdiff_t
@@ -58,6 +60,8 @@ using namespace gsl;
 
 namespace
 {
+static constexpr char deathstring[] = "Expected Death";
+
 struct BaseClass
 {
 };
@@ -75,7 +79,6 @@ struct AddressOverloaded
         return {};
     }
 };
-static const char *deathstring("Expected Death");
 } // namespace
 
 TEST(span_test, constructors)
@@ -1642,4 +1645,4 @@ TEST(span_test, from_array_constructor)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/strict_notnull_tests.cpp b/tests/strict_notnull_tests.cpp
index 766654b..a8d438a 100644
--- a/tests/strict_notnull_tests.cpp
+++ b/tests/strict_notnull_tests.cpp
@@ -27,12 +27,13 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 #include <gsl/pointers>           // for not_null, operator<, operator<=, operator>
@@ -143,7 +144,10 @@ TEST(strict_notnull_tests, TestStrictNotNull)
 }
 
 #if defined(__cplusplus) && (__cplusplus >= 201703L)
-static const char *deathstring("Expected Death");
+namespace
+{
+static constexpr char deathstring[] = "Expected Death";
+}
 
 TEST(strict_notnull_tests, TestStrictNotNullConstructorTypeDeduction)
 {
@@ -211,4 +215,4 @@ static_assert(std::is_nothrow_move_constructible<strict_not_null<void*>>::value,
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/strided_span_tests.cpp b/tests/strided_span_tests.cpp
index f87f1dc..20f14ad 100644
--- a/tests/strided_span_tests.cpp
+++ b/tests/strided_span_tests.cpp
@@ -25,18 +25,17 @@
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-
 //disable warnings from gtest
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
-
 #include <gsl/gsl_byte>   // for byte
 #include <gsl/gsl_util>   // for narrow_cast
 #include <gsl/multi_span> // for strided_span, index, multi_span, strided_...
@@ -47,16 +46,14 @@
 #include <type_traits> // for integral_constant<>::value, is_convertible
 #include <vector>      // for vector
 
-namespace gsl {
-struct fail_fast;
-}  // namespace gsl
-
 using namespace std;
 using namespace gsl;
 
+
 namespace
 {
-static const char *deathstring("Expected Death");
+static constexpr char deathstring[] = "Expected Death";
+
 struct BaseClass
 {
 };
@@ -815,4 +812,4 @@ TEST(strided_span_tests, strided_span_conversion)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/string_span_tests.cpp b/tests/string_span_tests.cpp
index 16bcf07..b9cfdcc 100644
--- a/tests/string_span_tests.cpp
+++ b/tests/string_span_tests.cpp
@@ -25,12 +25,13 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
 
 #include <gtest/gtest.h>
 
@@ -49,6 +50,10 @@
 using namespace std;
 using namespace gsl;
 
+namespace
+{
+static constexpr char deathstring[] = "Expected Death";
+}
 // Generic string functions
 
 namespace generic
@@ -72,7 +77,6 @@ auto strnlen(const CharT* s, std::size_t n)
 
 namespace
 {
-static const char *deathstring("Expected Death");
 
 template <typename T>
 T move_wrapper(T&& t)
@@ -1233,4 +1237,4 @@ TEST(string_span_tests, as_writeable_bytes)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__
diff --git a/tests/utils_tests.cpp b/tests/utils_tests.cpp
index 5911371..d779384 100644
--- a/tests/utils_tests.cpp
+++ b/tests/utils_tests.cpp
@@ -25,12 +25,14 @@
 //disable warnings from gtest
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wundef"
-#endif
+#endif // __clang__ || __GNUC__
+
 #if __clang__
 #pragma GCC diagnostic ignored "-Wglobal-constructors"
 #pragma GCC diagnostic ignored "-Wused-but-marked-unused"
 #pragma GCC diagnostic ignored "-Wcovered-switch-default"
-#endif
+#endif // __clang__
+
 
 #include <gtest/gtest.h>
 
@@ -44,8 +46,9 @@
 
 using namespace gsl;
 
-namespace{
-static const char *deathstring("Expected Death");
+namespace
+{
+static constexpr char deathstring[] = "Expected Death";
 void f(int& i) { i += 1; }
 static int j = 0;
 void g() { j += 1; }
@@ -153,4 +156,4 @@ TEST(utils_tests, narrow)
 
 #if __clang__ || __GNUC__
 #pragma GCC diagnostic pop
-#endif
+#endif // __clang__ || __GNUC__