diff --git a/tests/core/t_string.ml b/tests/core/t_string.ml
index 4db9bea5..f1747f1d 100644
--- a/tests/core/t_string.ml
+++ b/tests/core/t_string.ml
@@ -281,6 +281,18 @@ eq ~printer:CCFun.id "ab\nc\n" (unlines [ "ab"; "c" ]);;
 q Q.printable_string (fun s -> trim (unlines (lines s)) = trim s);;
 q Q.printable_string (fun s -> trim (unlines_gen (lines_gen s)) = trim s);;
 
+eq ~printer:CCFun.id "" (take_while (Char.equal 'c') "heloo_cc");;
+eq ~printer:CCFun.id "" (take_while (Char.equal 'c') "");;
+eq ~printer:CCFun.id "c" (take_while (Char.equal 'c') "c");;
+eq ~printer:CCFun.id "ccc" (take_while (Char.equal 'c') "cccujsuy");;
+eq ~printer:CCFun.id "THIS" (take_while (fun c -> Char.code c < 91) "THISisNotWHAtIwANTED");;
+
+eq ~printer:CCFun.id "cc" (rtake_while (Char.equal 'c') "heloo_cc");;
+eq ~printer:CCFun.id "" (rtake_while (Char.equal 'c') "");;
+eq ~printer:CCFun.id "c" (rtake_while (Char.equal 'c') "c");;
+eq ~printer:CCFun.id "" (rtake_while (Char.equal 'c') "cccujsuy");;
+eq ~printer:CCFun.id "ANTED" (rtake_while (fun c -> Char.code c < 91) "THISisNotWHAtIwANTED");;
+
 q
   Q.(small_list small_string)
   (fun l ->