test(sv): add remaining tests

include/c-libs/string-view.h

@@ -1,7 +1,9 @@
 #ifndef CLIBS_STRING_VIEW_H
 #define CLIBS_STRING_VIEW_H
 
+#include <assert.h>
 #include <malloc.h>
+#include <printf.h>
 #include <stddef.h>
 #include <stdio.h>
 #include <string.h>
@@ -198,8 +200,9 @@ StringView sv_new_sized(const char *str, size_t len) {
 StringView sv_new(const char *str) { return sv_new_sized(str, strlen(str)); }
 
 StringView sv_drop(StringView sv, size_t n) {
+  const char *nd = sv.data + n;
   return (StringView){
-      .data = sv.data + n,
+      .data = nd < sv.end ? nd : sv.end,
       .end = sv.end,
   };
 }
@@ -212,9 +215,10 @@ StringView sv_take(StringView sv, size_t n) {
 }
 
 StringView sv_shrink(StringView sv, size_t n) {
+  const char *ne = sv.end - n;
   return (StringView){
       .data = sv.data,
-      .end = sv.end - n,
+      .end = ne > sv.data ? ne : sv.data,
   };
 }
 
@@ -344,6 +348,10 @@ char *sv_concat_with_sep(const StringView *svs, size_t n, StringView sep) {
     write_head += l;
   }
 
+  *write_head = '\0';
+
+  assert(write_head - data == len - 1);
+
   return data;
 }