diff --git a/tests/src/string/main.c b/tests/src/string/main.c
index 4eb7e31..8b90e66 100644
--- a/tests/src/string/main.c
+++ b/tests/src/string/main.c
@@ -3,59 +3,65 @@
 
 #include "plug.h"
 
+static void string_print_compare(const vtype_string* s0, const vtype_string* s1) {
+    int c = string_compare(s0, s1);
+    char* m;
+    if (c == 0) m = "==";
+    else m = (c < 0) ? "<" : ">";
 
-static vtype_string string_random(unsigned int n) {
-    vtype_string x;
-
-    if (random_boolean()) {
-        x.buffer = random_utf8_cstring(n);
-    } else x.buffer = random_ascii_cstring(n);
-
-    return x;
+    puts("\e[36mStrings comparsion:\e[m\n");
+    printf("\e[33m\"%s\"\e[m \e[31m%s\e[m \e[33m\"%s\"\e[m\n", s0->buffer, m, s1->buffer);
 }
 
-static void string_concat_random(vtype_string* x, unsigned int n) {
-    char* v;
+static void string_print_case_compare(const vtype_string* s0, const vtype_string* s1) {
+    int c = string_case_compare(s0, s1);
+    char* m;
+    if (c == 0) m = "==";
+    else m = (c < 0) ? "<" : ">";
 
-    if (random_boolean()) {
-        v = random_utf8_cstring(n);
-    } else v = random_ascii_cstring(n);
-
-    string_concat(x, v);
-    free(v);
+    puts("\e[36mStrings case insensitive comparsion:\e[m\n");
+    printf("\e[33m\"%s\"\e[m \e[31m%s\e[m \e[33m\"%s\"\e[m\n", s0->buffer, m, s1->buffer);
 }
 
-static void string_info(vtype_string* x) {
-    printf("\e[36mString consists of \e[m\e[32m%lu\e[m\e[36m utf8 chars (\e[m\e[32m%lu bytes\e[m\e[36m)\e[m\n", string_size(x), string_nmemb(x));
-}
-
-static void string_print(const vtype_string* x, const char* prefix) {
-    if (!prefix) puts("\e[36mString content:\e[m\n");
-    else printf("\e[36mString %s content:\e[m\n\n", prefix);
-    printf("\e[33m%s\e[m\n", x->buffer);
-    put_separator();
-}
-
-
 int main(int argc, char** argv) {
     test_init(argc, argv);
-    vtype_string x;
+    vtype_string x, y;
 
-    x = string_random(31);
+    x = string_random(30);
     string_print(&x, "(part 1)");
 
     string_concat(&x, '\n');
-    string_concat_random(&x, 31);
+    string_concat_random(&x, 30);
 
     {
-        void* hack = string_at(&x, 32);
+        char* repl = random_utf8_cstring(30);
+        void* hack = string_at(&x, 31);
         string_print((void*)&hack, "(part 2)");
+        string_print((void*)&repl, "(part 2 replaced)");
+        string_replace(&x, hack, repl, -1);
+        free(repl);
     }
 
     string_info(&x);
     string_print(&x, "concatenated");
 
+    do {
+        string_replace_random(&x, 12);
+    } while (string_size(&x) == string_nmemb(&x));
 
+    y = string_copy(&x);
+
+    string_to_lower(&x);
+    string_to_upper(&y);
+
+    string_print_compare(&x, &y);
+    string_print_case_compare(&x, &y);
+
+    string_reverse(&y);
+    string_capitalize(&y);
+
+    string_print(&y, "reversed & capitalized");
 
     string_free(&x);
+    string_free(&y);
 }
diff --git a/tests/src/string/plug.h b/tests/src/string/plug.h
index c144b5e..d0fc750 100644
--- a/tests/src/string/plug.h
+++ b/tests/src/string/plug.h
@@ -47,3 +47,47 @@ static char* random_utf8_cstring(size_t size) {
     *p = 0;
     return v;
 }
+
+static void string_info(vtype_string* x) {
+    printf("\e[36mString consists of \e[m\e[32m%lu\e[m\e[36m utf8 chars (\e[m\e[32m%lu bytes\e[m\e[36m)\e[m\n", string_size(x), string_nmemb(x));
+}
+
+static void string_print(const vtype_string* x, const char* prefix) {
+    if (!prefix) puts("\e[36mString content:\e[m\n");
+    else printf("\e[36mString %s content:\e[m\n\n", prefix);
+    printf("\e[33m\"%s\"\e[m\n", x->buffer);
+    put_separator();
+}
+
+static vtype_string string_random(unsigned int n) {
+    vtype_string x;
+
+    if (random_boolean()) {
+        x.buffer = random_utf8_cstring(n);
+    } else x.buffer = random_ascii_cstring(n);
+
+    return x;
+}
+
+static void string_concat_random(vtype_string* x, unsigned int n) {
+    char* v;
+
+    if (random_boolean()) {
+        v = random_utf8_cstring(n);
+    } else v = random_ascii_cstring(n);
+
+    string_concat(x, v);
+    free(v);
+}
+
+static void string_replace_random(vtype_string* x, unsigned int n) {
+    char* v;
+
+    if (random_boolean()) {
+        v = random_utf8_cstring(n);
+    } else v = random_ascii_cstring(n);
+
+    string_replace(x, x, v, -1);
+
+    free(v);
+}
diff --git a/tests/src/string/trim.c b/tests/src/string/trim.c
new file mode 100644
index 0000000..a320ce8
--- /dev/null
+++ b/tests/src/string/trim.c
@@ -0,0 +1,20 @@
+/* This software is licensed by the MIT License, see LICENSE file */
+/*                                Copyright © 2022 Gregory Lirent */
+
+#include "plug.h"
+
+int main(int argc, char** argv) {
+    test_init(argc, argv);
+    vtype_string x;
+
+    x = string_random(12);
+
+    string_align_center(&x, 30, 0);
+
+    string_print(&x, 0);
+
+    string_trim(&x, 0);
+    string_print(&x, 0);
+
+    string_free(&x);
+}