ch10

ch10/__init__.py

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+# __init__.py
+# This is here to enable you to run tests within the `test` folder.

ch10/api.py

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+# api.py
+import os
+import csv
+from copy import deepcopy
+
+from marshmallow import Schema, fields, pre_load
+from marshmallow.validate import Length, Range
+
+
+class UserSchema(Schema):
+    """Represent a *valid* user. """
+
+    email = fields.Email(required=True)
+    name = fields.Str(required=True, validate=Length(min=1))
+    age = fields.Int(
+        required=True, validate=Range(min=18, max=65)
+    )
+    role = fields.Str()
+
+    @pre_load()
+    def strip_name(self, data, **kwargs):
+        data_copy = deepcopy(data)
+
+        try:
+            data_copy['name'] = data_copy['name'].strip()
+        except (AttributeError, KeyError, TypeError):
+            pass
+
+        return data_copy
+
+
+schema = UserSchema()
+
+
+def export(filename, users, overwrite=True):
+    """Export a CSV file.
+
+    Create a CSV file and fill with valid users.  If `overwrite`
+    is False and file already exists, raise IOError.
+    """
+    if not overwrite and os.path.isfile(filename):
+        raise IOError(f"'{filename}' already exists.")
+
+    valid_users = get_valid_users(users)
+    write_csv(filename, valid_users)
+
+
+def get_valid_users(users):
+    """Yield one valid user at a time from users. """
+    yield from filter(is_valid, users)
+
+
+def is_valid(user):
+    """Return whether or not the user is valid. """
+    return not schema.validate(user)
+
+
+def write_csv(filename, users):
+    """Write a CSV given a filename and a list of users.
+
+    The users are assumed to be valid for the given CSV structure.
+    """
+    fieldnames = ['email', 'name', 'age', 'role']
+
+    with open(filename, 'w', newline='') as csvfile:
+        writer = csv.DictWriter(csvfile, fieldnames=fieldnames)
+        writer.writeheader()
+
+        for user in users:
+            writer.writerow(user)

ch10/data.py

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+# data.py
+def get_clean_data(source):
+
+    data = load_data(source)
+    cleaned_data = clean_data(data)
+
+    return cleaned_data

ch10/requirements/requirements.in

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+marshmallow
+pytest

ch10/requirements/requirements.txt

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+#
+# This file is autogenerated by pip-compile
+# To update, run:
+#
+#    pip-compile requirements.in
+#
+attrs==21.2.0
+    # via pytest
+iniconfig==1.1.1
+    # via pytest
+marshmallow==3.12.1
+    # via -r requirements.in
+packaging==20.9
+    # via pytest
+pluggy==0.13.1
+    # via pytest
+py==1.10.0
+    # via pytest
+pyparsing==2.4.7
+    # via packaging
+pytest==6.2.4
+    # via -r requirements.in
+toml==0.10.2
+    # via pytest

ch10/tests/__init__.py

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+# tests/__init__.py

ch10/tests/test_api.py

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+# tests/test_api.py
+import re
+from unittest.mock import patch, mock_open, call
+
+import pytest
+
+from ch10.api import is_valid, export, write_csv
+
+
+@pytest.fixture
+def min_user():
+    """Represent a valid user with minimal data. """
+    return {
+        'email': 'minimal@example.com',
+        'name': 'Primus Minimus',
+        'age': 18,
+    }
+
+
+@pytest.fixture
+def full_user():
+    """Represent valid user with full data. """
+    return {
+        'email': 'full@example.com',
+        'name': 'Maximus Plenus',
+        'age': 65,
+        'role': 'emperor',
+    }
+
+
+@pytest.fixture
+def users(min_user, full_user):
+    """List of users, two valid and one invalid. """
+    bad_user = {
+        'email': 'invalid@example.com',
+        'name': 'Horribilis',
+    }
+    return [min_user, bad_user, full_user]
+
+
+class TestIsValid:
+    """Test how code verifies whether a user is valid or not. """
+
+    def test_minimal(self, min_user):
+        assert is_valid(min_user)
+
+    def test_full(self, full_user):
+        assert is_valid(full_user)
+
+    @pytest.mark.parametrize('age', range(18))
+    def test_invalid_age_too_young(self, age, min_user):
+        min_user['age'] = age
+
+        assert not is_valid(min_user)
+
+    @pytest.mark.parametrize('age', range(66, 100))
+    def test_invalid_age_too_old(self, age, min_user):
+        min_user['age'] = age
+
+        assert not is_valid(min_user)
+
+    @pytest.mark.parametrize('age', ['NaN', 3.1415, None])
+    def test_invalid_age_wrong_type(self, age, min_user):
+        min_user['age'] = age
+
+        assert not is_valid(min_user)
+
+    @pytest.mark.parametrize('age', range(18, 66))
+    def test_valid_age(self, age, min_user):
+        min_user['age'] = age
+
+        assert is_valid(min_user)
+
+    @pytest.mark.parametrize('field', ['email', 'name', 'age'])
+    def test_mandatory_fields(self, field, min_user):
+        del min_user[field]
+
+        assert not is_valid(min_user)
+
+    @pytest.mark.parametrize('field', ['email', 'name', 'age'])
+    def test_mandatory_fields_empty(self, field, min_user):
+        min_user[field] = ''
+
+        assert not is_valid(min_user)
+
+    def test_name_whitespace_only(self, min_user):
+        min_user['name'] = ' \n\t'
+
+        assert not is_valid(min_user)
+
+    @pytest.mark.parametrize(
+        'email, outcome',
+        [
+            ('missing_at.com', False),
+            ('@missing_start.com', False),
+            ('missing_end@', False),
+            ('missing_dot@example', False),
+
+            ('good.one@example.com', True),
+            ('δοκιμή@παράδειγμα.δοκιμή', True),
+            ('аджай@экзампл.рус', True),
+        ]
+    )
+    def test_email(self, email, outcome, min_user):
+        min_user['email'] = email
+
+        assert is_valid(min_user) == outcome
+
+    @pytest.mark.parametrize(
+        'field, value',
+        [
+            ('email', None),
+            ('email', 3.1415),
+            ('email', {}),
+
+            ('name', None),
+            ('name', 3.1415),
+            ('name', {}),
+
+            ('role', None),
+            ('role', 3.1415),
+            ('role', {}),
+        ]
+    )
+    def test_invalid_types(self, field, value, min_user):
+        min_user[field] = value
+
+        assert not is_valid(min_user)
+
+
+class TestExport:
+    """Test behavior of `export` function. """
+
+    @pytest.fixture
+    def csv_file(self, tmp_path):
+        """Yield a filename in a temporary folder.
+
+        Due to how pytest `tmp_path` fixture works, the file does
+        not exist yet.
+        """
+        yield tmp_path / "out.csv"
+
+    @pytest.fixture
+    def existing_file(self, tmp_path):
+        """Create a temporary file and put some content in it. """
+        existing = tmp_path / 'existing.csv'
+        existing.write_text('Please leave me alone...')
+        yield existing
+
+    def test_export(self, users, csv_file):
+        export(csv_file, users)
+
+        text = csv_file.read_text()
+
+        assert (
+            'email,name,age,role\n'
+            'minimal@example.com,Primus Minimus,18,\n'
+            'full@example.com,Maximus Plenus,65,emperor\n'
+         ) == text
+
+    def test_export_quoting(self, min_user, csv_file):
+        min_user['name'] = 'A name, with a comma'
+
+        export(csv_file, [min_user])
+
+        text = csv_file.read_text()
+
+        assert (
+            'email,name,age,role\n'
+            'minimal@example.com,"A name, with a comma",18,\n'
+         ) == text
+
+    def test_does_not_overwrite(self, users, existing_file):
+        with pytest.raises(IOError) as err:
+            export(existing_file, users, overwrite=False)
+
+        err.match(
+            r"'{}' already exists\.".format(
+                re.escape(str(existing_file))
+            )
+        )
+
+        # let's also verify the file is still intact
+        assert existing_file.read_text() == (
+            'Please leave me alone...'
+        )
+
+
+class TextExportMock:
+    """Example on how to test with mocks. """
+
+    @pytest.fixture
+    def write_csv_mock(self):
+        with patch('ch10.api.write_csv') as m:
+            yield m
+
+    @pytest.fixture
+    def get_valid_users_mock(self):
+        with patch('ch10.api.get_valid_users') as m:
+            yield m
+
+    def test_export(
+        self, write_csv_mock, get_valid_users_mock, users
+    ):
+        export('out.csv', users)
+
+        # verify mocked funcs have been called properly
+        assert [call(users)] == get_valid_users_mock.call_args_list
+
+        valid_users = get_valid_users_mock.return_value
+        assert [
+            call('out.csv', valid_users)
+        ] == write_csv_mock.call_args_list
+
+
+class TestWriteCSV:
+    """Example on how to test with mocks. """
+
+    @pytest.fixture
+    def open_mock(self):
+        """Mocks the `open` function. """
+        with patch('builtins.open', new_callable=mock_open()) as m:
+            yield m
+
+    @pytest.fixture
+    def csv_mock(self):
+        """Mocks the `csv` module as imported in `api.py`. """
+        with patch('ch10.api.csv') as m:
+            yield m
+
+    def test_write_csv(self, open_mock, csv_mock, users):
+        fieldnames = ['email', 'name', 'age', 'role']
+
+        write_csv('out.csv', users)
+
+        # verify both mocks are at work properly
+        writer = csv_mock.DictWriter.return_value
+        managed = open_mock().__enter__()
+
+        assert [
+            call(managed, fieldnames=fieldnames)
+        ] == csv_mock.DictWriter.call_args_list
+
+        assert [call()] == writer.writeheader.call_args_list
+
+        assert [
+            call(users[0]), call(users[1]), call(users[2])
+        ] == writer.writerow.call_args_list