diff --git a/src/functional/string_memmem.c b/src/functional/string_memmem.c
index 005045b..608eadf 100644
--- a/src/functional/string_memmem.c
+++ b/src/functional/string_memmem.c
@@ -51,6 +51,9 @@ int main(void)
 	T("abababa", "bababa", 1)
 	T("abababab", "bababab", 1)
 	T("ababababa", "babababa", 1)
+	T("abbababab", "bababa", 2)
+	T("abbababab", "ababab", 3)
+	T("abacabcabcab", "abcabcab", 4)
 	T("nanabanabanana", "aba", 3)
 	T("nanabanabanana", "ban", 4)
 	T("nanabanabanana", "anab", 1)
diff --git a/src/functional/string_strstr.c b/src/functional/string_strstr.c
index 67aeaab..54e0fd5 100644
--- a/src/functional/string_strstr.c
+++ b/src/functional/string_strstr.c
@@ -45,6 +45,9 @@ int main(void)
 	T("abababa", "bababa", 1)
 	T("abababab", "bababab", 1)
 	T("ababababa", "babababa", 1)
+	T("abbababab", "bababa", 2)
+	T("abbababab", "ababab", 3)
+	T("abacabcabcab", "abcabcab", 4)
 	T("nanabanabanana", "aba", 3)
 	T("nanabanabanana", "ban", 4)
 	T("nanabanabanana", "anab", 1)
diff --git a/src/functional/wcsstr.c b/src/functional/wcsstr.c
new file mode 100644
index 0000000..73be607
--- /dev/null
+++ b/src/functional/wcsstr.c
@@ -0,0 +1,58 @@
+#include <wchar.h>
+#include "test.h"
+
+#define N(s, sub) { \
+	wchar_t *p = s; \
+	wchar_t *q = wcsstr(p, sub); \
+	if (q) \
+		t_error("wcsstr(%s,%s) returned str+%d, wanted 0\n", #s, #sub, q-p); \
+}
+
+#define T(s, sub, n) { \
+	wchar_t *p = s; \
+	wchar_t *q = wcsstr(p, sub); \
+	if (q == 0) \
+		t_error("wcsstr(%s,%s) returned 0, wanted str+%d\n", #s, #sub, n); \
+	else if (q - p != n) \
+		t_error("wcsstr(%s,%s) returned str+%d, wanted str+%d\n", #s, #sub, q-p, n); \
+}
+
+int main(void)
+{
+	N(L"", L"a")
+	N(L"a", L"aa")
+	N(L"a", L"b")
+	N(L"aa", L"ab")
+	N(L"aa", L"aaa")
+	N(L"abba", L"aba")
+	N(L"abc abc", L"abcd")
+	N(L"0-1-2-3-4-5-6-7-8-9", L"-3-4-56-7-8-")
+	N(L"0-1-2-3-4-5-6-7-8-9", L"-3-4-5+6-7-8-")
+	N(L"_ _ _\xff_ _ _", L"_\x7f_")
+	N(L"_ _ _\x7f_ _ _", L"_\xff_")
+
+	T(L"", L"", 0)
+	T(L"abcd", L"", 0)
+	T(L"abcd", L"a", 0)
+	T(L"abcd", L"b", 1)
+	T(L"abcd", L"c", 2)
+	T(L"abcd", L"d", 3)
+	T(L"abcd", L"ab", 0)
+	T(L"abcd", L"bc", 1)
+	T(L"abcd", L"cd", 2)
+	T(L"ababa", L"baba", 1)
+	T(L"ababab", L"babab", 1)
+	T(L"abababa", L"bababa", 1)
+	T(L"abababab", L"bababab", 1)
+	T(L"ababababa", L"babababa", 1)
+	T(L"abbababab", L"bababa", 2)
+	T(L"abbababab", L"ababab", 3)
+	T(L"abacabcabcab", L"abcabcab", 4)
+	T(L"nanabanabanana", L"aba", 3)
+	T(L"nanabanabanana", L"ban", 4)
+	T(L"nanabanabanana", L"anab", 1)
+	T(L"nanabanabanana", L"banana", 8)
+	T(L"_ _\xff_ _", L"_\xff_", 2)
+
+	return t_status;
+}