Added the first basic test

cucumbers.py

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+"""
+This module contains a simple class modeling a cucumber basket.
+Cucumbers may be added or removed from the basket.
+The basket has a maximum size, however.
+"""
+
+
+class CucumberBasket:
+
+    def __init__(self, initial_count=0, max_count=10):
+        if initial_count < 0:
+            raise ValueError("Initial cucumber basket count must not be negative")
+        if max_count < 0:
+            raise ValueError("Max cucumber basket count must not be negative")
+
+        self._count = initial_count
+        self._max_count = max_count
+
+    @property
+    def count(self):
+        return self._count
+
+    @property
+    def full(self):
+        return self.count == self.max_count
+
+    @property
+    def empty(self):
+        return self.count == 0
+
+    @property
+    def max_count(self):
+        return self._max_count
+
+    def add(self, count=1):
+        new_count = self.count + count
+        if new_count > self.max_count:
+            raise ValueError("Attempted to add too many cucumbers")
+        self._count = new_count
+
+    def remove(self, count=1):
+        new_count = self.count - count
+        if new_count < 0:
+            raise ValueError("Attempted to remove too many cucumbers")
+        self._count = new_count

tests/features/cucumbers.feature

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+Feature: Cucumber Basket
+  As a gardener,
+  I want to carry cucumbers in a basket,
+  So that I don't drop them all.
+
+
+  Scenario: Add cucumbers to a basket
+    Given the basket has 2 cucumbers
+    When 4 cucumbers are added to the basket
+    Then the basket contains 6 cucumbers

tests/step_defs/test_cucumbers_steps.py

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+from pytest_bdd import scenario, given, when, then
+
+from cucumbers import CucumberBasket
+
+
+@scenario('../features/cucumbers.feature', 'Add cucumbers to a basket')
+def test_add():
+  pass
+
+
+@given("the basket has 2 cucumbers", target_fixture='basket')
+def basket():
+  return CucumberBasket(initial_count=2)
+
+
+@when("4 cucumbers are added to the basket")
+def add_cucumbers(basket):
+  basket.add(4)
+
+
+@then("the basket contains 6 cucumbers")
+def basket_has_total(basket):
+  assert basket.count == 6