diff --git a/explainaboard/analysis/feature_funcs.py b/explainaboard/analysis/feature_funcs.py
index 2b5ec275..e89e3f09 100644
--- a/explainaboard/analysis/feature_funcs.py
+++ b/explainaboard/analysis/feature_funcs.py
@@ -11,7 +11,7 @@
 from explainaboard.info import SysOutputInfo
 from explainaboard.utils import basic_words
 from explainaboard.utils.logging import progress
-from explainaboard.utils.tokenizer import Tokenizer
+from explainaboard.utils.tokenizer import SingleSpaceTokenizer, Tokenizer
 from explainaboard.utils.typing_utils import unwrap
 
 
@@ -68,17 +68,10 @@ def get_basic_words(text: str) -> float:
     Returns:
         The ratio of basic words.
     """
-    value_list = text.split(' ')
-    n_words = len(value_list)
-    n_basic_words = 0
-
-    for word in value_list:
-
-        lower = word.lower()
-        if lower in basic_words.BASIC_WORDS:
-            n_basic_words = n_basic_words + 1
-
-    return n_basic_words * 1.0 / n_words
+    tokens = SingleSpaceTokenizer()(text)
+    assert len(tokens) > 0, f"BUG: no tokens obtained from the text: '{text}'"
+    n_basic_words = sum(1 for t in tokens if t.lower() in basic_words.BASIC_WORDS)
+    return n_basic_words / len(tokens)
 
 
 def get_lexical_richness(text: str) -> float:
diff --git a/explainaboard/analysis/feature_funcs_test.py b/explainaboard/analysis/feature_funcs_test.py
new file mode 100644
index 00000000..3e4f8827
--- /dev/null
+++ b/explainaboard/analysis/feature_funcs_test.py
@@ -0,0 +1,35 @@
+"""Tests for explainaboard.analysis.feature_funcs."""
+
+
+import unittest
+
+from explainaboard.analysis.feature_funcs import get_basic_words
+
+
+class FeatureFuncsTest(unittest.TestCase):
+    def test_get_basic_words(self) -> None:
+        # All examples should exactly match.
+
+        # zero word
+        self.assertEqual(get_basic_words(""), 0.0)
+        self.assertEqual(get_basic_words(" "), 0.0)
+
+        # one word
+        self.assertEqual(get_basic_words("the"), 1.0)
+        self.assertEqual(get_basic_words(" the"), 0.5)
+        self.assertEqual(get_basic_words(" the "), 1 / 3)
+        self.assertEqual(get_basic_words("USA"), 0.0)
+
+        # two words
+        self.assertEqual(get_basic_words("United States"), 0.0)
+        self.assertEqual(get_basic_words("The USA"), 0.5)
+        self.assertEqual(get_basic_words("The country"), 1.0)
+
+        # check capitalization
+        self.assertEqual(get_basic_words("The THE the tHE"), 1.0)
+
+        # check punctuation
+        self.assertEqual(get_basic_words("It is."), 0.5)
+        self.assertEqual(get_basic_words("It is ."), 2 / 3)
+        self.assertEqual(get_basic_words("It, is"), 0.5)
+        self.assertEqual(get_basic_words("It , is"), 2 / 3)
diff --git a/explainaboard/utils/tokenizer_test.py b/explainaboard/utils/tokenizer_test.py
index f07f0e0c..467350d4 100644
--- a/explainaboard/utils/tokenizer_test.py
+++ b/explainaboard/utils/tokenizer_test.py
@@ -44,6 +44,38 @@ def test_from_orig_and_tokens_invalid(self) -> None:
 
 
 class TokenizerSerializerTest(unittest.TestCase):
+    def test_empty(self) -> None:
+        tokens = SingleSpaceTokenizer()("")
+        self.assertEqual(len(tokens), 1)
+        self.assertEqual(tokens.strs, [""])
+        self.assertEqual(tokens.positions, [0])
+
+    def test_only_0x20(self) -> None:
+        tokens = SingleSpaceTokenizer()("   ")
+        self.assertEqual(len(tokens), 4)
+        self.assertEqual(tokens.strs, ["", "", "", ""])
+        self.assertEqual(tokens.positions, [0, 1, 2, 3])
+
+    def test_isspace(self) -> None:
+        tokens = SingleSpaceTokenizer()("\t\v \n\r\f")
+        self.assertEqual(len(tokens), 2)
+        self.assertEqual(tokens.strs, ["\t\v", "\n\r\f"])
+        self.assertEqual(tokens.positions, [0, 3])
+
+    def test_sentence(self) -> None:
+        tokens = SingleSpaceTokenizer()("May the force be with you.")
+        self.assertEqual(len(tokens), 6)
+        self.assertEqual(tokens.strs, ["May", "the", "force", "be", "with", "you."])
+        self.assertEqual(tokens.positions, [0, 4, 8, 14, 17, 22])
+
+    def test_sentence_with_extra_whitespaces(self) -> None:
+        tokens = SingleSpaceTokenizer()(" May  the force\nbe with you. ")
+        self.assertEqual(len(tokens), 8)
+        self.assertEqual(
+            tokens.strs, ["", "May", "", "the", "force\nbe", "with", "you.", ""]
+        )
+        self.assertEqual(tokens.positions, [0, 1, 5, 6, 10, 19, 24, 29])
+
     def test_serialize(self) -> None:
         serializer = PrimitiveSerializer()
         self.assertEqual(