Revert "Delete solutions/tests/test_word_frequency.py"

This reverts commit 8512058.

solutions/tests/test_word_frequency.py

@@ -0,0 +1,37 @@
+# test_word_frequency.py
+"""
+This module contains unit tests for the word_frequency module.
+
+The tests verify the functionality of the count_word_frequency function,
+which counts the frequency of words in a given text.
+"""
+
+import unittest
+
+from ..word_frequency import count_word_frequency
+
+
+class TestWordFrequency(unittest.TestCase):
+    """Test cases for the count_word_frequency function."""
+
+    def test_count_word_frequency(self):
+        """Test counting word frequency in a simple text."""
+        text = "hello world hello"
+        expected_output = {"hello": 2, "world": 1}
+        self.assertEqual(count_word_frequency(text), expected_output)
+
+    def test_empty_text(self):
+        """Test counting word frequency in an empty string."""
+        text = ""
+        expected_output = {}
+        self.assertEqual(count_word_frequency(text), expected_output)
+
+    def test_case_insensitive(self):
+        """Test counting word frequency with case-insensitive matching."""
+        text = "Hello hello HeLLo"
+        expected_output = {"hello": 3}
+        self.assertEqual(count_word_frequency(text), expected_output)
+
+
+if __name__ == "__main__":
+    unittest.main()