From: Richard Russon <rich@flatcap.org>
Date: Mon, 15 Apr 2019 23:48:39 +0000 (+0100)
Subject: test: add string tests for degenerate cases
X-Git-Tag: 2019-10-25~266^2~3
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d821ca856a750afafc40e6f86e0ae49cfcbabbbc;p=neomutt

test: add string tests for degenerate cases
---

diff --git a/test/string/mutt_str_adjust.c b/test/string/mutt_str_adjust.c
index 09fd64994..86c69d233 100644
--- a/test/string/mutt_str_adjust.c
+++ b/test/string/mutt_str_adjust.c
@@ -28,4 +28,15 @@
 void test_mutt_str_adjust(void)
 {
   // void mutt_str_adjust(char **p);
+
+  {
+    mutt_str_adjust(NULL);
+    TEST_CHECK_(1, "mutt_str_adjust(NULL)");
+  }
+
+  {
+    char *ptr = NULL;
+    mutt_str_adjust(&ptr);
+    TEST_CHECK_(1, "mutt_str_adjust(&ptr)");
+  }
 }
diff --git a/test/string/mutt_str_append_item.c b/test/string/mutt_str_append_item.c
index f44386450..3eed69d5b 100644
--- a/test/string/mutt_str_append_item.c
+++ b/test/string/mutt_str_append_item.c
@@ -28,4 +28,15 @@
 void test_mutt_str_append_item(void)
 {
   // void mutt_str_append_item(char **str, const char *item, int sep);
+
+  {
+    mutt_str_append_item(NULL, "apple", ',');
+    TEST_CHECK_(1, "mutt_str_append_item(NULL, \"apple\", ',')");
+  }
+
+  {
+    char *ptr = NULL;
+    mutt_str_append_item(&ptr, NULL, ',');
+    TEST_CHECK_(1, "mutt_str_append_item(&ptr, NULL, ',')");
+  }
 }
diff --git a/test/string/mutt_str_asprintf.c b/test/string/mutt_str_asprintf.c
index b7b8c59cc..cdf4fda60 100644
--- a/test/string/mutt_str_asprintf.c
+++ b/test/string/mutt_str_asprintf.c
@@ -23,8 +23,23 @@
 #define TEST_NO_MAIN
 #include "acutest.h"
 #include "config.h"
+#include "mutt/mutt.h"
 
 void test_mutt_str_asprintf(void)
 {
   // int mutt_str_asprintf(char **strp, const char *fmt, ...);
+
+  {
+    TEST_CHECK(mutt_str_asprintf(NULL, "dummy") == -1);
+  }
+
+  {
+    char *ptr = NULL;
+    TEST_CHECK(mutt_str_asprintf(&ptr, "dummy") == -1);
+  }
+
+  {
+    char *ptr = NULL;
+    TEST_CHECK(mutt_str_asprintf(&ptr, NULL) == -1);
+  }
 }
diff --git a/test/string/mutt_str_atoi.c b/test/string/mutt_str_atoi.c
index edf8ce10e..25c906a7e 100644
--- a/test/string/mutt_str_atoi.c
+++ b/test/string/mutt_str_atoi.c
@@ -28,4 +28,8 @@
 void test_mutt_str_atoi(void)
 {
   // int mutt_str_atoi(const char *str, int *dst);
+
+  {
+    TEST_CHECK(mutt_str_atoi(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_atol.c b/test/string/mutt_str_atol.c
index 0bd7c0f41..e3a727a41 100644
--- a/test/string/mutt_str_atol.c
+++ b/test/string/mutt_str_atol.c
@@ -28,4 +28,8 @@
 void test_mutt_str_atol(void)
 {
   // int mutt_str_atol(const char *str, long *dst);
+
+  {
+    TEST_CHECK(mutt_str_atol(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_atos.c b/test/string/mutt_str_atos.c
index 3424a577d..e25dc4a74 100644
--- a/test/string/mutt_str_atos.c
+++ b/test/string/mutt_str_atos.c
@@ -28,4 +28,8 @@
 void test_mutt_str_atos(void)
 {
   // int mutt_str_atos(const char *str, short *dst);
+
+  {
+    TEST_CHECK(mutt_str_atos(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_atoui.c b/test/string/mutt_str_atoui.c
index 0631fd4db..8c83ef2c0 100644
--- a/test/string/mutt_str_atoui.c
+++ b/test/string/mutt_str_atoui.c
@@ -28,4 +28,8 @@
 void test_mutt_str_atoui(void)
 {
   // int mutt_str_atoui(const char *str, unsigned int *dst);
+
+  {
+    TEST_CHECK(mutt_str_atoui(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_atoul.c b/test/string/mutt_str_atoul.c
index 3e0b62673..5ec4b8889 100644
--- a/test/string/mutt_str_atoul.c
+++ b/test/string/mutt_str_atoul.c
@@ -28,4 +28,8 @@
 void test_mutt_str_atoul(void)
 {
   // int mutt_str_atoul(const char *str, unsigned long *dst);
+
+  {
+    TEST_CHECK(mutt_str_atoul(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_atoull.c b/test/string/mutt_str_atoull.c
index b5e5f4733..192ddf6af 100644
--- a/test/string/mutt_str_atoull.c
+++ b/test/string/mutt_str_atoull.c
@@ -28,4 +28,8 @@
 void test_mutt_str_atoull(void)
 {
   // int mutt_str_atoull(const char *str, unsigned long long *dst);
+
+  {
+    TEST_CHECK(mutt_str_atoull(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_dequote_comment.c b/test/string/mutt_str_dequote_comment.c
index 56924eb9c..8e4b19b6d 100644
--- a/test/string/mutt_str_dequote_comment.c
+++ b/test/string/mutt_str_dequote_comment.c
@@ -28,4 +28,10 @@
 void test_mutt_str_dequote_comment(void)
 {
   // void mutt_str_dequote_comment(char *s);
+
+  {
+    mutt_str_dequote_comment(NULL);
+    TEST_CHECK_(1, "mutt_str_dequote_comment(NULL)");
+  }
+
 }
diff --git a/test/string/mutt_str_find_word.c b/test/string/mutt_str_find_word.c
index 603da3050..d45cdd22d 100644
--- a/test/string/mutt_str_find_word.c
+++ b/test/string/mutt_str_find_word.c
@@ -28,4 +28,8 @@
 void test_mutt_str_find_word(void)
 {
   // const char *mutt_str_find_word(const char *src);
+
+  {
+    TEST_CHECK(mutt_str_find_word(NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_getenv.c b/test/string/mutt_str_getenv.c
index e9f09e3cd..b8116113f 100644
--- a/test/string/mutt_str_getenv.c
+++ b/test/string/mutt_str_getenv.c
@@ -28,4 +28,8 @@
 void test_mutt_str_getenv(void)
 {
   // const char *mutt_str_getenv(const char *name);
+
+  {
+    TEST_CHECK(mutt_str_getenv(NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_inline_replace.c b/test/string/mutt_str_inline_replace.c
index d799fc72c..1c275e738 100644
--- a/test/string/mutt_str_inline_replace.c
+++ b/test/string/mutt_str_inline_replace.c
@@ -28,4 +28,13 @@
 void test_mutt_str_inline_replace(void)
 {
   // bool mutt_str_inline_replace(char *buf, size_t buflen, size_t xlen, const char *rstr);
+
+  {
+    TEST_CHECK(mutt_str_inline_replace(NULL, 10, 2, "apple") == false);
+  }
+
+  {
+    char buf[32] = "banana";
+    TEST_CHECK(mutt_str_inline_replace(buf, sizeof(buf), 2, NULL) == false);
+  }
 }
diff --git a/test/string/mutt_str_is_ascii.c b/test/string/mutt_str_is_ascii.c
index 38f5dc277..333f1497b 100644
--- a/test/string/mutt_str_is_ascii.c
+++ b/test/string/mutt_str_is_ascii.c
@@ -28,4 +28,8 @@
 void test_mutt_str_is_ascii(void)
 {
   // bool mutt_str_is_ascii(const char *p, size_t len);
+
+  {
+    TEST_CHECK(mutt_str_is_ascii(NULL, 10) == true);
+  }
 }
diff --git a/test/string/mutt_str_lws_len.c b/test/string/mutt_str_lws_len.c
index b39c296e2..e6b0eadd3 100644
--- a/test/string/mutt_str_lws_len.c
+++ b/test/string/mutt_str_lws_len.c
@@ -28,4 +28,8 @@
 void test_mutt_str_lws_len(void)
 {
   // size_t mutt_str_lws_len(const char *s, size_t n);
+
+  {
+    TEST_CHECK(mutt_str_lws_len(NULL, 10) == 0);
+  }
 }
diff --git a/test/string/mutt_str_lws_rlen.c b/test/string/mutt_str_lws_rlen.c
index b33fba657..faa55bec7 100644
--- a/test/string/mutt_str_lws_rlen.c
+++ b/test/string/mutt_str_lws_rlen.c
@@ -28,4 +28,8 @@
 void test_mutt_str_lws_rlen(void)
 {
   // size_t mutt_str_lws_rlen(const char *s, size_t n);
+
+  {
+    TEST_CHECK(mutt_str_lws_rlen(NULL, 10) == 0);
+  }
 }
diff --git a/test/string/mutt_str_next_word.c b/test/string/mutt_str_next_word.c
index 3d256adbe..0794090e5 100644
--- a/test/string/mutt_str_next_word.c
+++ b/test/string/mutt_str_next_word.c
@@ -28,4 +28,8 @@
 void test_mutt_str_next_word(void)
 {
   // const char *mutt_str_next_word(const char *s);
+
+  {
+    TEST_CHECK(mutt_str_next_word(NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_pretty_size.c b/test/string/mutt_str_pretty_size.c
index f08ece3d9..1b73e1c62 100644
--- a/test/string/mutt_str_pretty_size.c
+++ b/test/string/mutt_str_pretty_size.c
@@ -28,4 +28,9 @@
 void test_mutt_str_pretty_size(void)
 {
   // void mutt_str_pretty_size(char *buf, size_t buflen, size_t num);
+
+  {
+    mutt_str_pretty_size(NULL, 10, 1234);
+    TEST_CHECK_(1, "mutt_str_pretty_size(NULL, 10, 1234)");
+  }
 }
diff --git a/test/string/mutt_str_remall_strcasestr.c b/test/string/mutt_str_remall_strcasestr.c
index b1c800c94..5da76e92b 100644
--- a/test/string/mutt_str_remall_strcasestr.c
+++ b/test/string/mutt_str_remall_strcasestr.c
@@ -28,4 +28,16 @@
 void test_mutt_str_remall_strcasestr(void)
 {
   // int mutt_str_remall_strcasestr(char *str, const char *target);
+
+  {
+    TEST_CHECK(mutt_str_remall_strcasestr(NULL, "apple") == 1);
+  }
+
+  {
+    TEST_CHECK(mutt_str_remall_strcasestr("apple", NULL) == 1);
+  }
+
+  {
+    TEST_CHECK(mutt_str_remall_strcasestr(NULL, NULL) == 1);
+  }
 }
diff --git a/test/string/mutt_str_remove_trailing_ws.c b/test/string/mutt_str_remove_trailing_ws.c
index 3ea564a2e..6cb8dffe4 100644
--- a/test/string/mutt_str_remove_trailing_ws.c
+++ b/test/string/mutt_str_remove_trailing_ws.c
@@ -28,4 +28,9 @@
 void test_mutt_str_remove_trailing_ws(void)
 {
   // void mutt_str_remove_trailing_ws(char *s);
+
+  {
+    mutt_str_remove_trailing_ws(NULL);
+    TEST_CHECK_(1, "mutt_str_remove_trailing_ws(NULL)");
+  }
 }
diff --git a/test/string/mutt_str_replace.c b/test/string/mutt_str_replace.c
index 30f8361e9..878c0d91e 100644
--- a/test/string/mutt_str_replace.c
+++ b/test/string/mutt_str_replace.c
@@ -28,4 +28,20 @@
 void test_mutt_str_replace(void)
 {
   // void mutt_str_replace(char **p, const char *s);
+
+  {
+    mutt_str_replace(NULL, NULL);
+    TEST_CHECK_(1, "mutt_str_replace(NULL, NULL)");
+  }
+
+  {
+    mutt_str_replace(NULL, "apple");
+    TEST_CHECK_(1, "mutt_str_replace(NULL, \"apple\")");
+  }
+
+  {
+    char *ptr = NULL;
+    mutt_str_replace(&ptr, NULL);
+    TEST_CHECK_(1, "mutt_str_replace(&ptr, NULL)");
+  }
 }
diff --git a/test/string/mutt_str_rstrnstr.c b/test/string/mutt_str_rstrnstr.c
index e4d10cfa6..bfd46f4b4 100644
--- a/test/string/mutt_str_rstrnstr.c
+++ b/test/string/mutt_str_rstrnstr.c
@@ -28,4 +28,12 @@
 void test_mutt_str_rstrnstr(void)
 {
   // const char *mutt_str_rstrnstr(const char *haystack, size_t haystack_length, const char *needle);
+
+  {
+    TEST_CHECK(mutt_str_rstrnstr(NULL, 10, "apple") == NULL);
+  }
+
+  {
+    TEST_CHECK(mutt_str_rstrnstr("apple", 10, NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_skip_email_wsp.c b/test/string/mutt_str_skip_email_wsp.c
index 48d41fc28..1c122ff8f 100644
--- a/test/string/mutt_str_skip_email_wsp.c
+++ b/test/string/mutt_str_skip_email_wsp.c
@@ -28,4 +28,8 @@
 void test_mutt_str_skip_email_wsp(void)
 {
   // char *mutt_str_skip_email_wsp(const char *s);
+
+  {
+    TEST_CHECK(mutt_str_skip_email_wsp(NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_skip_whitespace.c b/test/string/mutt_str_skip_whitespace.c
index 1f66181ac..abe944fe9 100644
--- a/test/string/mutt_str_skip_whitespace.c
+++ b/test/string/mutt_str_skip_whitespace.c
@@ -28,4 +28,8 @@
 void test_mutt_str_skip_whitespace(void)
 {
   // char *mutt_str_skip_whitespace(char *p);
+
+  {
+    TEST_CHECK(mutt_str_skip_whitespace(NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_split.c b/test/string/mutt_str_split.c
index 9bd793ded..2b2d04925 100644
--- a/test/string/mutt_str_split.c
+++ b/test/string/mutt_str_split.c
@@ -28,4 +28,9 @@
 void test_mutt_str_split(void)
 {
   // struct ListHead mutt_str_split(const char *src, char sep);
+
+  {
+    struct ListHead head = mutt_str_split(NULL, ',');
+    TEST_CHECK(STAILQ_EMPTY(&head));
+  }
 }
diff --git a/test/string/mutt_str_startswith.c b/test/string/mutt_str_startswith.c
index 7634e63af..92bdd9023 100644
--- a/test/string/mutt_str_startswith.c
+++ b/test/string/mutt_str_startswith.c
@@ -28,4 +28,12 @@
 void test_mutt_str_startswith(void)
 {
   // size_t mutt_str_startswith(const char *str, const char *prefix, enum CaseSensitivity cs);
+
+  {
+    TEST_CHECK(mutt_str_startswith(NULL, "apple", CASE_MATCH) == 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_startswith("apple", NULL, CASE_MATCH) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strcasecmp.c b/test/string/mutt_str_strcasecmp.c
index 9a36eca12..6d01db4a7 100644
--- a/test/string/mutt_str_strcasecmp.c
+++ b/test/string/mutt_str_strcasecmp.c
@@ -28,4 +28,16 @@
 void test_mutt_str_strcasecmp(void)
 {
   // int mutt_str_strcasecmp(const char *a, const char *b);
+
+  {
+    TEST_CHECK(mutt_str_strcasecmp(NULL, "apple") != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcasecmp("apple", NULL) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcasecmp(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strcasestr.c b/test/string/mutt_str_strcasestr.c
index 2dde38a6c..df9af9a60 100644
--- a/test/string/mutt_str_strcasestr.c
+++ b/test/string/mutt_str_strcasestr.c
@@ -28,4 +28,16 @@
 void test_mutt_str_strcasestr(void)
 {
   // const char *mutt_str_strcasestr(const char *haystack, const char *needle);
+
+  {
+    TEST_CHECK(mutt_str_strcasestr(NULL, "apple") == NULL);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcasestr("apple", NULL) == NULL);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcasestr(NULL, NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_strcat.c b/test/string/mutt_str_strcat.c
index d12ee747e..dd5313d11 100644
--- a/test/string/mutt_str_strcat.c
+++ b/test/string/mutt_str_strcat.c
@@ -28,4 +28,13 @@
 void test_mutt_str_strcat(void)
 {
   // char *mutt_str_strcat(char *buf, size_t buflen, const char *s);
+
+  {
+    TEST_CHECK(mutt_str_strcat(NULL, 10, "apple") == NULL);
+  }
+
+  {
+    char buf[32] = { 0 };
+    TEST_CHECK(mutt_str_strcat(buf, sizeof(buf), NULL) == buf);
+  }
 }
diff --git a/test/string/mutt_str_strchrnul.c b/test/string/mutt_str_strchrnul.c
index af8e7bca6..1fe9e6fc2 100644
--- a/test/string/mutt_str_strchrnul.c
+++ b/test/string/mutt_str_strchrnul.c
@@ -28,4 +28,8 @@
 void test_mutt_str_strchrnul(void)
 {
   // const char *mutt_str_strchrnul(const char *s, char c);
+
+  {
+    TEST_CHECK(mutt_str_strchrnul(NULL, 'a') == NULL);
+  }
 }
diff --git a/test/string/mutt_str_strcmp.c b/test/string/mutt_str_strcmp.c
index fd6ee1d46..402bbe8cd 100644
--- a/test/string/mutt_str_strcmp.c
+++ b/test/string/mutt_str_strcmp.c
@@ -28,4 +28,16 @@
 void test_mutt_str_strcmp(void)
 {
   // int mutt_str_strcmp(const char *a, const char *b);
+
+  {
+    TEST_CHECK(mutt_str_strcmp(NULL, "apple") != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcmp("apple", NULL) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcmp(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strcoll.c b/test/string/mutt_str_strcoll.c
index 827eed1dc..88ab0ba99 100644
--- a/test/string/mutt_str_strcoll.c
+++ b/test/string/mutt_str_strcoll.c
@@ -28,4 +28,16 @@
 void test_mutt_str_strcoll(void)
 {
   // int mutt_str_strcoll(const char *a, const char *b);
+
+  {
+    TEST_CHECK(mutt_str_strcoll(NULL, "apple") != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcoll("apple", NULL) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strcoll(NULL, NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strdup.c b/test/string/mutt_str_strdup.c
index 4fc4c4e37..f1baf6762 100644
--- a/test/string/mutt_str_strdup.c
+++ b/test/string/mutt_str_strdup.c
@@ -28,4 +28,13 @@
 void test_mutt_str_strdup(void)
 {
   // char *mutt_str_strdup(const char *str);
+
+  {
+    TEST_CHECK(mutt_str_strdup(NULL) == NULL);
+  }
+
+  {
+    char *ptr = NULL;
+    TEST_CHECK(mutt_str_strdup(ptr) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_strfcpy.c b/test/string/mutt_str_strfcpy.c
index 8d742b86f..0962d0364 100644
--- a/test/string/mutt_str_strfcpy.c
+++ b/test/string/mutt_str_strfcpy.c
@@ -28,4 +28,13 @@
 void test_mutt_str_strfcpy(void)
 {
   // size_t mutt_str_strfcpy(char *dest, const char *src, size_t dsize);
+
+  {
+    TEST_CHECK(mutt_str_strfcpy(NULL, "apple", 10) == 0);
+  }
+
+  {
+    char buf[32] = { 0 };
+    TEST_CHECK(mutt_str_strfcpy(buf, NULL, sizeof(buf)) == 0);
+  }
 }
diff --git a/test/string/mutt_str_stristr.c b/test/string/mutt_str_stristr.c
index 9ce561d90..3f6eb0ad2 100644
--- a/test/string/mutt_str_stristr.c
+++ b/test/string/mutt_str_stristr.c
@@ -28,4 +28,17 @@
 void test_mutt_str_stristr(void)
 {
   // const char *mutt_str_stristr(const char *haystack, const char *needle);
+
+  {
+    TEST_CHECK(mutt_str_stristr(NULL, "apple") == NULL);
+  }
+
+  {
+    char *haystack = "apple";
+    TEST_CHECK(mutt_str_stristr(haystack, NULL) == haystack);
+  }
+
+  {
+    TEST_CHECK(mutt_str_stristr(NULL, NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_strlen.c b/test/string/mutt_str_strlen.c
index 3d29c993b..2f2d171b8 100644
--- a/test/string/mutt_str_strlen.c
+++ b/test/string/mutt_str_strlen.c
@@ -28,4 +28,8 @@
 void test_mutt_str_strlen(void)
 {
   // size_t mutt_str_strlen(const char *a);
+
+  {
+    TEST_CHECK(mutt_str_strlen(NULL) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strlower.c b/test/string/mutt_str_strlower.c
index 6915a876f..6e7714310 100644
--- a/test/string/mutt_str_strlower.c
+++ b/test/string/mutt_str_strlower.c
@@ -28,4 +28,8 @@
 void test_mutt_str_strlower(void)
 {
   // char *mutt_str_strlower(char *s);
+
+  {
+    TEST_CHECK(mutt_str_strlower(NULL) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_strncasecmp.c b/test/string/mutt_str_strncasecmp.c
index 7acd1a643..7cf565b9c 100644
--- a/test/string/mutt_str_strncasecmp.c
+++ b/test/string/mutt_str_strncasecmp.c
@@ -28,4 +28,16 @@
 void test_mutt_str_strncasecmp(void)
 {
   // int mutt_str_strncasecmp(const char *a, const char *b, size_t l);
+
+  {
+    TEST_CHECK(mutt_str_strncasecmp(NULL, "apple", 3) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strncasecmp("apple", NULL, 3) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strncasecmp(NULL, NULL, 3) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strncat.c b/test/string/mutt_str_strncat.c
index 843529136..f239fde70 100644
--- a/test/string/mutt_str_strncat.c
+++ b/test/string/mutt_str_strncat.c
@@ -28,4 +28,17 @@
 void test_mutt_str_strncat(void)
 {
   // char *mutt_str_strncat(char *d, size_t l, const char *s, size_t sl);
+
+  {
+    TEST_CHECK(mutt_str_strncat(NULL, 10, "apple", 5) == NULL);
+  }
+
+  {
+    char buf[32] = { 0 };
+    TEST_CHECK(mutt_str_strncat(buf, sizeof(buf), NULL, 5) == buf);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strncat(NULL, 10, NULL, 5) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_strncmp.c b/test/string/mutt_str_strncmp.c
index ad494ba38..3270bf133 100644
--- a/test/string/mutt_str_strncmp.c
+++ b/test/string/mutt_str_strncmp.c
@@ -28,4 +28,16 @@
 void test_mutt_str_strncmp(void)
 {
   // int mutt_str_strncmp(const char *a, const char *b, size_t l);
+
+  {
+    TEST_CHECK(mutt_str_strncmp(NULL, "apple", 5) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strncmp("apple", NULL, 5) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strncmp(NULL, NULL, 5) == 0);
+  }
 }
diff --git a/test/string/mutt_str_strnfcpy.c b/test/string/mutt_str_strnfcpy.c
index 81f19610a..165db4657 100644
--- a/test/string/mutt_str_strnfcpy.c
+++ b/test/string/mutt_str_strnfcpy.c
@@ -28,4 +28,17 @@
 void test_mutt_str_strnfcpy(void)
 {
   // size_t mutt_str_strnfcpy(char *dest, const char *src, size_t n, size_t dsize);
+
+  {
+    TEST_CHECK(mutt_str_strnfcpy(NULL, "apple", 5, 10) == 0);
+  }
+
+  {
+    char buf[32] = { 0 };
+    TEST_CHECK(mutt_str_strnfcpy(buf, NULL, 5, sizeof(buf)) == 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_strnfcpy(NULL, NULL, 5, 10) == 0);
+  }
 }
diff --git a/test/string/mutt_str_substr_cpy.c b/test/string/mutt_str_substr_cpy.c
index a325e4a30..c0d685988 100644
--- a/test/string/mutt_str_substr_cpy.c
+++ b/test/string/mutt_str_substr_cpy.c
@@ -28,4 +28,20 @@
 void test_mutt_str_substr_cpy(void)
 {
   // char *mutt_str_substr_cpy(char *dest, const char *begin, const char *end, size_t destlen);
+
+  const char *str = "apple banana";
+
+  {
+    TEST_CHECK(mutt_str_substr_cpy(NULL, str + 3, str + 7, 32) == NULL);
+  }
+
+  {
+    char buf[32] = { 0 };
+    TEST_CHECK(mutt_str_substr_cpy(buf, NULL, str + 7, sizeof(buf)) == buf);
+  }
+
+  {
+    char buf[32] = { 0 };
+    TEST_CHECK(mutt_str_substr_cpy(buf, str + 3, NULL, sizeof(buf)) == buf);
+  }
 }
diff --git a/test/string/mutt_str_substr_dup.c b/test/string/mutt_str_substr_dup.c
index 5d88726ef..c51cc63e6 100644
--- a/test/string/mutt_str_substr_dup.c
+++ b/test/string/mutt_str_substr_dup.c
@@ -28,4 +28,10 @@
 void test_mutt_str_substr_dup(void)
 {
   // char *mutt_str_substr_dup(const char *begin, const char *end);
+
+  const char *str = "apple banana";
+
+  {
+    TEST_CHECK(mutt_str_substr_dup(NULL, str + 7) == NULL);
+  }
 }
diff --git a/test/string/mutt_str_word_casecmp.c b/test/string/mutt_str_word_casecmp.c
index e2c68000f..86dfe2eb9 100644
--- a/test/string/mutt_str_word_casecmp.c
+++ b/test/string/mutt_str_word_casecmp.c
@@ -28,4 +28,16 @@
 void test_mutt_str_word_casecmp(void)
 {
   // int mutt_str_word_casecmp(const char *a, const char *b);
+
+  {
+    TEST_CHECK(mutt_str_word_casecmp(NULL, "apple") != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_word_casecmp("apple", NULL) != 0);
+  }
+
+  {
+    TEST_CHECK(mutt_str_word_casecmp(NULL, NULL) == 0);
+  }
 }