diff --git a/banana/bananalib.py b/banana/bananalib.py
index d3967f5..21dc175 100644
--- a/banana/bananalib.py
+++ b/banana/bananalib.py
@@ -42,6 +42,22 @@ def decoder(banana, dictstart=0, shiftend=0, dictionary=None):
     return v
 
 
+def is_valid(banana, dictstart=0, shiftend=0, dictionary=None):
+    # defaults
+    if dictionary is None:
+        dictionary = [list("bcdfglmnprstvz"), list("aeiou")]  # , list("123456")
+
+    numdict = len(dictionary)
+    if (len(banana) - shiftend) % numdict != 0:
+        return False
+    for i in range(len(banana)):
+        r = (numdict + i + dictstart) % numdict
+        if banana[i] not in dictionary[r]:
+            return False
+
+    return True
+
+
 def banana2dec(word):
     return decoder(word)
 
@@ -50,6 +66,10 @@ def dec2banana(word):
     return encoder(word)
 
 
+def isbanana(word):
+    return is_valid(word)
+
+
 def ribes2dec(word):
     return decoder(word, 0, 1)
 
@@ -58,6 +78,10 @@ def dec2ribes(word):
     return encoder(word, 0, 1)
 
 
+def isribes(word):
+    return is_valid(word, 0, 1)
+
+
 def avocado2dec(word):
     return decoder(word, 1, 1)
 
@@ -66,6 +90,10 @@ def dec2avocado(word):
     return encoder(word, 1, 1)
 
 
+def isavocado(word):
+    return is_valid(word, 1, 1)
+
+
 def ananas2dec(word):
     return decoder(word, 1, 0)
 
@@ -74,6 +102,10 @@ def dec2ananas(word):
     return encoder(word, 1, 0)
 
 
+def isananas(word):
+    return is_valid(word, 1, 0)
+
+
 def bananarandom(dictstart=0, shiftend=0, minlength=6, dictionary=None):
     import random
 
@@ -95,21 +127,5 @@ def bananarandom(dictstart=0, shiftend=0, minlength=6, dictionary=None):
     return st
 
 
-def isbanana(banana, dictstart=0, shiftend=0, dictionary=None):
-    # defaults
-    if dictionary is None:
-        dictionary = [list("bcdfglmnprstvz"), list("aeiou")]  # , list("123456")
-
-    numdict = len(dictionary)
-    if (len(banana) - shiftend) % numdict != 0:
-        return False
-    for i in range(len(banana)):
-        r = (numdict + i + dictstart) % numdict
-        if banana[i] not in dictionary[r]:
-            return False
-
-    return True
-
-
 if __name__ == "__main__":
     print("Ciao sono la libreria banana")
diff --git a/banana/cli.py b/banana/cli.py
index 31e0e06..c5666ec 100644
--- a/banana/cli.py
+++ b/banana/cli.py
@@ -118,7 +118,7 @@ def isbanana():
     )
     args = parser.parse_args()
 
-    print(banana.isbanana(args.banana, args.dictstart, args.shiftend, args.dictionary))
+    print(banana.isbanana(args.banana))
 
 
 def main():
diff --git a/tests/test_banana.py b/tests/test_banana.py
index c78f30c..ae406c9 100644
--- a/tests/test_banana.py
+++ b/tests/test_banana.py
@@ -4,7 +4,8 @@
 import pytest
 
 from banana import (ananas2dec, avocado2dec, banana2dec, dec2ananas,
-                    dec2avocado, dec2banana, dec2ribes, ribes2dec)
+                    dec2avocado, dec2banana, dec2ribes, isananas, isavocado,
+                    isbanana, isribes, ribes2dec)
 
 banana_conversions = {"be": 1, "beba": 70, "zu": 69, "bezu": 139, "nana": 2485}
 
@@ -88,6 +89,16 @@ def test_dec_to_banana_known(banana_known):
     assert dec2banana(value) == word
 
 
+def test_banana_is_banana(banana_known):
+    assert isbanana(banana_known[0])
+
+
+def test_banana_is_only_banana(banana_known):
+    assert not isribes(banana_known[0])
+    assert not isananas(banana_known[0])
+    assert not isavocado(banana_known[0])
+
+
 def test_banana2dec_prefix_ba(banana_known):
     """un ba all'inizio non cambia nulla!"""
     word, value = banana_known
@@ -105,6 +116,16 @@ def test_dec_to_ribes_known(ribes_known):
     assert dec2ribes(value) == word
 
 
+def test_ribes_is_ribes(ribes_known):
+    assert isribes(ribes_known[0])
+
+
+def test_ribes_is_only_ribes(ribes_known):
+    assert not isbanana(ribes_known[0])
+    assert not isananas(ribes_known[0])
+    assert not isavocado(ribes_known[0])
+
+
 def test_avocado_to_dec_known(avocado_known):
     word, value = avocado_known
     assert avocado2dec(word) == value
@@ -115,6 +136,16 @@ def test_dec_to_avocado_known(avocado_known):
     assert dec2avocado(value) == word
 
 
+def test_avocado_is_avocado(avocado_known):
+    assert isavocado(avocado_known[0])
+
+
+def test_avocado_is_only_avocado(avocado_known):
+    assert not isribes(avocado_known[0])
+    assert not isananas(avocado_known[0])
+    assert not isbanana(avocado_known[0])
+
+
 def test_ananas_to_dec_known(ananas_known):
     word, value = ananas_known
     assert ananas2dec(word) == value
@@ -125,6 +156,16 @@ def test_dec_to_ananas_known(ananas_known):
     assert dec2ananas(value) == word
 
 
+def test_ananas_is_ananas(ananas_known):
+    assert isananas(ananas_known[0])
+
+
+def test_ananas_is_only_ananas(ananas_known):
+    assert not isribes(ananas_known[0])
+    assert not isbanana(ananas_known[0])
+    assert not isbanana(ananas_known[0])
+
+
 def test_answer_to_life_the_universe_and_everything():
     banana = banana2dec("banana")
     assert banana != 42