diff --git a/tdd_practice_001.py b/tdd_practice_001.py
new file mode 100644
index 0000000..86be0f4
--- /dev/null
+++ b/tdd_practice_001.py
@@ -0,0 +1,86 @@
+def increment_string(string):
+    """
+       Description: Increment the numeric suffix of a string.
+
+    If the string ends with a number, increment that number by 1.
+    If the string does not end with a number, append 1.
+    Examples:
+
+    "foo" -> "foo1"
+    "foobar23" -> "foobar24"
+    "foo0042" -> "foo0043"
+    "foo9" -> "foo10"
+    """
+
+    num = ""
+    if len(string) == 0 or not string[-1].isdigit():
+        return string + str(1)
+    for i in range(len(string)):
+        if string[len(string) - 1 - i].isalpha():
+            break
+        idx = len(string) - 1 - i
+        num += string[len(string) - 1 - i]
+    return f"{string[:idx]}{int(num[::-1]) + 1:0{len(num)}d}"
+
+
+def count_letters(string):
+    """
+       Description: Count the occurrences of each letter in a string.
+
+    Example::
+
+    "aba" -> {"a": 2, "b": 1}
+    """
+
+    occurance = {}
+    for char in string:
+        char = char.lower()
+        occurance[char] = string.lower().count(char)
+    return occurance
+
+
+def sum_consecutives(s):
+    """
+    Description: Return a list of sums of each consecutive pair in a list.
+
+    Example:
+
+    [1, 2, 3] -> [3, 5]  # 1+2=3, 2+3=5
+    """
+    sum = []
+    for idx, num in enumerate(s):
+        if idx + 1 < len(s) and not (is_number(num) and is_number(s[idx + 1])):
+            raise ValueError("The list must be numerical list.")
+        if idx + 1 < len(s):
+            sum.append(num + s[idx + 1])
+    return sum
+
+
+def is_number(s):
+    try:
+        float(s)
+        return True
+    except ValueError:
+        return False
+
+
+def count_unique(text):
+    '''
+    Description: Count the number of unique words in a string.
+
+    Should raise a ValueError if the input is not a string.
+
+    Example:
+
+    "no example ;)"'''
+
+    if not isinstance(text, str):
+        raise ValueError("Input must be a string")
+
+    words = text.lower().split()
+    # unique_words = set(words)
+    unique_words = []
+    for word in words:
+        if len(word) > 1 and word not in unique_words and word.isalpha():
+            unique_words.append(word)
+    return len(unique_words)
diff --git a/tests.py b/tests.py
new file mode 100644
index 0000000..878ddfe
--- /dev/null
+++ b/tests.py
@@ -0,0 +1,107 @@
+from unittest import TestCase, main
+from tdd_practice_001 import (
+    increment_string,
+    count_letters,
+    sum_consecutives,
+    count_unique,
+)
+
+
+class TestIcrementString(TestCase):
+
+    def test_append_one(self):
+        string1 = ""
+        string2 = "abcd"
+        self.assertEqual(increment_string(string1), "1")
+        self.assertEqual(increment_string(string2), "abcd1")
+
+    def test_add_one(self):
+        string1 = "abcde123"
+        string2 = "0123"
+        self.assertEqual(increment_string(string1), "abcde124")
+        self.assertEqual(increment_string(string2), "0124")
+
+    def test_none(self): ...
+
+
+class TestCountLetters(TestCase):
+
+    def test_count_empty(self):
+        """count letter in an empty string"""
+        self.assertDictEqual(count_letters(""), {})
+
+    def test_count_letters(self):
+        string = "karabo"
+        string1 = "string is None, "
+        self.assertDictEqual(
+            count_letters(string), {"k": 1, "a": 2, "r": 1, "b": 1, "o": 1}
+        )
+        self.assertDictEqual(
+            count_letters(string1),
+            {
+                "s": 2,
+                "t": 1,
+                "r": 1,
+                "n": 3,
+                "g": 1,
+                "i": 2,
+                "o": 1,
+                "e": 1,
+                " ": 3,
+                ",": 1,
+            },
+        )
+
+    def test_type_return(self):
+        "Testing if it return a dictionary"
+        self.assertIsInstance(count_letters(""), dict)
+
+
+class TestSumConsecutives(TestCase):
+
+    def test_empty_list(self):
+        self.assertListEqual(sum_consecutives([]), [])
+
+    def test_returned_type(self):
+        "Testing if it return a list"
+        self.assertIsInstance((sum_consecutives([])), list)
+
+    def test_mixed_list(self):
+        with self.assertRaises(ValueError):
+            sum_consecutives([1, 23.23, "gmail"])
+
+    def test_num_list(self):
+        self.assertListEqual(sum_consecutives([2, 3, 5, 6]), [5, 8, 11])
+        self.assertListEqual(sum_consecutives([0.5, 1]), [1.5])
+
+
+class TestCountUniqueWords(TestCase):
+
+    def test_basic_example(self):
+        self.assertEqual(count_unique("no example ;)"), 2)
+
+    def test_case_insensitivity(self):
+        self.assertEqual(count_unique("Hello hello world"), 2)
+
+    def test_empty_string(self):
+        self.assertEqual(count_unique(""), 0)
+
+    def test_single_word(self):
+        self.assertEqual(count_unique("Python"), 1)
+
+    def test_multiple_unique_words(self):
+        self.assertEqual(count_unique("one two three four"), 4)
+
+    def test_repeated_words(self):
+        self.assertEqual(count_unique("test test test"), 1)
+
+    def test_non_string_input(self):
+        with self.assertRaises(ValueError):
+            count_unique(12345)
+
+    def test_string_with_punctuation(self):
+        self.assertEqual(count_unique("word, word"), 2)
+
+
+if __name__ == "__main__":
+    main(verbosity=2)