diff --git a/base64/base64.c b/base64/base64.c
index 7cb907a..abbfdb6 100644
--- a/base64/base64.c
+++ b/base64/base64.c
@@ -39,7 +39,8 @@ static const uint8_t base64_decode_map[] = {
 // todo: fix encoding for strings with length < 3
 const char *const base64_encode(const uint8_t *const data, size_t data_size) {
   const size_t remaining = data_size % 3;
-  const size_t base64_len = ceil(((double)data_size * 8) / 6) + 1;
+  const size_t base64_len =
+      ((double)data_size * 8) / 6 + 4 /* maximum padding + null char */;
   char *result = malloc(base64_len);
   if (!result) {
     return NULL;
diff --git a/base64/maintest.c b/base64/maintest.c
index 71a0ad6..cee6bcb 100644
--- a/base64/maintest.c
+++ b/base64/maintest.c
@@ -5,7 +5,7 @@
 #include <string.h>
 
 int main(void) {
-  const char *decodee = "light w";
+  const char *decodee = "this is some long sentence to be encoded in base64.";
   char *encoded = (char *)base64_encode((uint8_t *)decodee, strlen(decodee));
   char *decoded = (char *)base64_decode(encoded, strlen(encoded));
   assert(strcmp(decodee, decoded) == 0);
@@ -13,33 +13,27 @@ int main(void) {
   free((void *)encoded);
   free((void *)decoded);
 
-  // -------
-
-  encoded = (char *)base64_encode((uint8_t *)"Man", 3);
-  assert(strcmp(encoded, "TWFu") == 0);
-  decoded = (char *)base64_decode(encoded, strlen(encoded));
-  assert(strcmp(decoded, "Man") == 0);
-  free((void *)encoded);
-  free((void *)decoded);
-
-  // ------
-
-  encoded = (char *)base64_encode((uint8_t *)"light work.", 11);
-  assert(strcmp(encoded, "bGlnaHQgd29yay4=") == 0);
-  decoded = (char *)base64_decode(encoded, strlen(encoded));
-  assert(strcmp(decoded, "light work.") == 0);
-  free((void *)encoded);
-  free((void *)decoded);
-
   // ------
 
-  // todo: still crashing atm as function fails for args with len < 3
-  // encoded = (char *)base64_encode((uint8_t *)"ma", 2);
-  // assert(strcmp(encoded, "TWE=") == 0);
-  // decoded = (char *)base64_decode(encoded, strlen(encoded));
-  // assert(strcmp(decoded, "TWE=") == 0);
-  // free((void *)encoded);
-  // free((void *)decoded);
+  struct {
+    char *encoded;
+    char *decoded;
+  } res[] = {
+      {.decoded = "Man", .encoded = "TWFu"},
+      {.decoded = "light work.", .encoded = "bGlnaHQgd29yay4="},
+      {.decoded = "ma", .encoded = "bWE="},
+  };
+
+  for (size_t i = 0; i < sizeof(res) / sizeof(res[0]); i++) {
+    encoded = (char *)base64_encode((uint8_t *)res[i].decoded,
+                                    strlen(res[i].decoded));
+    assert(strcmp(encoded, res[i].encoded) == 0);
+    decoded = (char *)base64_decode(encoded, strlen(encoded));
+    assert(strcmp(decoded, res[i].decoded) == 0);
+
+    free(encoded);
+    free(decoded);
+  }
 
   puts("tests passed.");
   return 0;