freadln.c: add a test

c-programming/io/freadln.c

@@ -68,3 +68,16 @@ int freadln(char** output, size_t* length_out) {
 	errno = 0;
 	freadln_success_epilogue;
 }
+
+#ifdef TEST
+int main(void) {
+	printf("Type something> ");
+	char* line;
+	if (freadln(&line, NULL) != freadln_OK) {
+		perror("freadln");
+		exit(EXIT_FAILURE);
+	}
+	printf("Input string: '%s'\n", line);
+	return 0;
+}
+#endif