diff --git a/libcxx/src/debug.cpp b/libcxx/src/debug.cpp
--- a/libcxx/src/debug.cpp
+++ b/libcxx/src/debug.cpp
@@ -438,7 +438,7 @@
     __i_node* j = __find_iterator(__j);
     __c_node* ci = i != nullptr ? i->__c_ : nullptr;
     __c_node* cj = j != nullptr ? j->__c_ : nullptr;
-    return ci != nullptr && ci == cj;
+    return ci == cj;
 }
 
 void
diff --git a/libcxx/test/std/strings/basic.string/string.iterators/iterators.pass.cpp b/libcxx/test/std/strings/basic.string/string.iterators/iterators.pass.cpp
--- a/libcxx/test/std/strings/basic.string/string.iterators/iterators.pass.cpp
+++ b/libcxx/test/std/strings/basic.string/string.iterators/iterators.pass.cpp
@@ -22,69 +22,46 @@
 
 #include "test_macros.h"
 
-int main(int, char**)
+template<class C>
+void test()
 {
     { // N3644 testing
-        typedef std::string C;
-        C::iterator ii1{}, ii2{};
-        C::iterator ii4 = ii1;
-        C::const_iterator cii{};
+        typename C::iterator ii1{}, ii2{};
+        typename C::iterator ii4 = ii1;
+        typename C::const_iterator cii{};
         assert ( ii1 == ii2 );
         assert ( ii1 == ii4 );
-        assert ( ii1 == cii );
-        assert ( !(ii1 != ii2 ));
-        assert ( !(ii1 != cii ));
-    }
 
-    { // N3644 testing
-        typedef std::wstring C;
-        C::iterator ii1{}, ii2{};
-        C::iterator ii4 = ii1;
-        C::const_iterator cii{};
-        assert ( ii1 == ii2 );
-        assert ( ii1 == ii4 );
-        assert ( ii1 == cii );
-        assert ( !(ii1 != ii2 ));
-        assert ( !(ii1 != cii ));
+        assert (!(ii1 != ii2 ));
+
+        assert ( (ii1 == cii ));
+        assert ( (cii == ii1 ));
+        assert (!(ii1 != cii ));
+        assert (!(cii != ii1 ));
+        assert (!(ii1 <  cii ));
+        assert (!(cii <  ii1 ));
+        assert ( (ii1 <= cii ));
+        assert ( (cii <= ii1 ));
+        assert (!(ii1 >  cii ));
+        assert (!(cii >  ii1 ));
+        assert ( (ii1 >= cii ));
+        assert ( (cii >= ii1 ));
+        assert (cii - ii1 == 0);
+        assert (ii1 - cii == 0);
     }
+}
+
+int main(int, char**)
+{
+    test<std::string>();
+    test<std::wstring>();
 
 #if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
-    {
-        typedef std::u8string C;
-        C::iterator ii1{}, ii2{};
-        C::iterator ii4 = ii1;
-        C::const_iterator cii{};
-        assert ( ii1 == ii2 );
-        assert ( ii1 == ii4 );
-        assert ( ii1 == cii );
-        assert ( !(ii1 != ii2 ));
-        assert ( !(ii1 != cii ));
-    }
+    test<std::u8string>();
 #endif
 
-    { // N3644 testing
-        typedef std::u16string C;
-        C::iterator ii1{}, ii2{};
-        C::iterator ii4 = ii1;
-        C::const_iterator cii{};
-        assert ( ii1 == ii2 );
-        assert ( ii1 == ii4 );
-        assert ( ii1 == cii );
-        assert ( !(ii1 != ii2 ));
-        assert ( !(ii1 != cii ));
-    }
-
-    { // N3644 testing
-        typedef std::u32string C;
-        C::iterator ii1{}, ii2{};
-        C::iterator ii4 = ii1;
-        C::const_iterator cii{};
-        assert ( ii1 == ii2 );
-        assert ( ii1 == ii4 );
-        assert ( ii1 == cii );
-        assert ( !(ii1 != ii2 ));
-        assert ( !(ii1 != cii ));
-    }
+    test<std::u16string>();
+    test<std::u32string>();
 
-  return 0;
+    return 0;
 }