Added basic tests.

.gitignore

@@ -0,0 +1,2 @@
+__pycache__
+app.pyc tests.pyc

README.md

@@ -10,6 +10,8 @@ The solution is implemented in a single file, and it's targeting `python39`.
 To execute the example you can just run `python app.py` assuming you are using the correct version, and
 that you are located in the directory for this project.
 
+To execute tests you can run `python -m unittest tests.py` or `pytest tests.py` (provided you installed `pytest`).
+
 # About the solution
 
 The problem can be divided in two parts,

app.py

@@ -29,9 +29,7 @@ class Stats:
         This method executes in constant time, because
         it's a list access by element.
         """
-        returnable = self._list[value - 1]
-        # print(value, returnable)
-        return returnable
+        return self._list[value - 1]
 
     def between(self, m, M):
         """
@@ -39,7 +37,7 @@ class Stats:
         it's consuming two times a constant method,
         plus an arithmetic operation.
         """
-        return self.less(M + 1) - self.less(m - 1)
+        return self.less(M + 1) - self.less(m)
 
     def greater(self, value):
         """

tests.py

@@ -0,0 +1,78 @@
+from unittest import TestCase
+from app import DataCapture, Stats
+
+
+class TestDataCaptureStats(TestCase):
+    def test_init(self):
+        """Test no error at initialization."""
+        a = DataCapture()
+        assert isinstance(a, DataCapture)
+
+    def test_add_single_value(self):
+        """Test no error at add single value."""
+        a = DataCapture()
+        a.add(1)
+
+    def test_add_many_values(self):
+        """Test no error at add many values."""
+        a = DataCapture()
+        a.add(1, 2)
+
+    def test_generate_stats_zero(self):
+        """Test no error at add many values."""
+        a = DataCapture()
+        stats = a.build_stats()
+        assert isinstance(stats, Stats)
+
+    def test_generate_single_element_stats(self):
+        """Test no error at add many values."""
+        a = DataCapture()
+        a.add(1)
+        stats = a.build_stats()
+        assert isinstance(stats, Stats)
+
+    def test_generate_multi_element_stats(self):
+        """Test no error at add many values."""
+        a = DataCapture()
+        a.add(1, 2, 3, 4, 5, 6, 7)
+        stats = a.build_stats()
+        assert isinstance(stats, Stats)
+        assert 5 == stats.greater(2)
+        assert 4 == stats.less(5)
+        assert 4 == stats.between(2, 5)
+
+    def test_generate_multi_element_stats_v2(self):
+        """Test no error at add many values."""
+        a = DataCapture()
+        a.add(1, 2, 3, 4, 5, 6, 7)
+        a.add(1, 2, 3, 4, 5, 6, 7)
+        stats = a.build_stats()
+        assert isinstance(stats, Stats)
+        assert 10 == stats.greater(2)
+        assert 8 == stats.less(5)
+        assert 8 == stats.between(2, 5)
+
+    def test_generate_multi_element_stats_v3(self):
+        """Test no error at add many values."""
+        a = DataCapture()
+        a.add(1, 2, 3, 4, 5, 6, 7)
+        a.add(2, 4, 6, 8)
+        stats = a.build_stats()
+        assert isinstance(stats, Stats)
+        assert 6 == stats.less(5)
+        assert 6 == stats.between(2, 5)
+        assert 1 == stats.less(2)
+        assert 2 == stats.between(2, 2)
+        assert 8 == stats.greater(2)
+
+    def test_base_case(self):
+        capture = DataCapture()
+        capture.add(3)
+        capture.add(9)
+        capture.add(3)
+        capture.add(4)
+        capture.add(6)
+        stats = capture.build_stats()
+        assert 2 == stats.less(4)
+        assert 2 == stats.greater(4)
+        assert 4 == stats.between(3, 6)