Handle ampersand

Replaced with & in messages

test_util.c

@@ -0,0 +1,68 @@
+#include <stdlib.h>
+#include <head-unit.h>
+#include "util.h"
+
+void replace_one_substr(void)
+{
+    char *string = "it is a string";
+    char *sub = "is";
+    char *new = "was";
+
+    char *result = str_replace(string, sub, new);
+
+    assert_string_equals("it was a string", result);
+}
+
+void replace_one_substr_beginning(void)
+{
+    char *string = "it is a string";
+    char *sub = "it";
+    char *new = "that";
+
+    char *result = str_replace(string, sub, new);
+
+    assert_string_equals("that is a string", result);
+}
+
+void replace_one_substr_end(void)
+{
+    char *string = "it is a string";
+    char *sub = "string";
+    char *new = "thing";
+
+    char *result = str_replace(string, sub, new);
+
+    assert_string_equals("it is a thing", result);
+}
+
+void replace_two_substr(void)
+{
+    char *string = "it is a is string";
+    char *sub = "is";
+    char *new = "was";
+
+    char *result = str_replace(string, sub, new);
+
+    assert_string_equals("it was a was string", result);
+}
+
+void replace_char(void)
+{
+    char *string = "some & a thing & something else";
+    char *sub = "&";
+    char *new = "&amp;";
+
+    char *result = str_replace(string, sub, new);
+
+    assert_string_equals("some &amp; a thing &amp; something else", result);
+}
+
+void register_util_tests(void)
+{
+    TEST_MODULE("util tests");
+    TEST(replace_one_substr);
+    TEST(replace_one_substr_beginning);
+    TEST(replace_one_substr_end);
+    TEST(replace_two_substr);
+    TEST(replace_char);
+}