import unittest
import psycopg2
import pandas as pd

class TestPostgresQuery(unittest.TestCase):
    @classmethod
    def setUpClass(cls):
        cls.connection = psycopg2.connect(
            host="localhost",
            user="agent",
            password="qwerty",
            dbname="testdb",
            sslmode="disable"
        )
        cls.cursor = cls.connection.cursor()

    def get_query_result(self):
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        return pd.DataFrame(rows, columns=columns)

    def test_welcome_message_present(self):
        """Check that welcome_message column exists for all rows."""
        df = self.get_query_result()
        condition = 'welcome_message' in df.columns and df['welcome_message'].notnull().all()
        _dynamic_test(
            self,
            condition,
            "welcome_message column is present for all rows.",
            "welcome_message column is missing or contains NULL values."
        )

    def test_welcome_back_with_name(self):
        """Check 'Welcome back, [name]!' is returned for years_at_company > 1 and name is not NULL."""
        df = self.get_query_result()
        filtered = df[(df['years_at_company'] > 1) & (df['name'].notnull())]
        expected = [f"Welcome back, {row['name']}!" for _, row in filtered.iterrows()]
        actual = list(filtered['welcome_message'])
        condition = expected == actual
        _dynamic_test(
            self,
            condition,
            "Correct 'Welcome back, [name]!' for years > 1.",
            "Incorrect 'Welcome back, [name]!' for years > 1."
        )

    def test_welcome_with_name(self):
        """Check 'Welcome, [name]!' is returned for years_at_company <= 1 and name is not NULL."""
        df = self.get_query_result()
        filtered = df[(df['years_at_company'] <= 1) & (df['name'].notnull())]
        expected = [f"Welcome, {row['name']}!" for _, row in filtered.iterrows()]
        actual = list(filtered['welcome_message'])
        condition = expected == actual
        _dynamic_test(
            self,
            condition,
            "Correct 'Welcome, [name]!' for years <= 1.",
            "Incorrect 'Welcome, [name]!' for years <= 1."
        )

    def test_welcome_back_there(self):
        """Check 'Welcome back, there!' is returned for years_at_company > 1 and name is NULL."""
        # Insert a NULL name row for testing
        self.cursor.execute("INSERT INTO employees (id, name, department, salary, years_at_company) VALUES (100, NULL, 'Test', 50000, 2) ON CONFLICT DO NOTHING;")
        df = self.get_query_result()
        filtered = df[(df['years_at_company'] > 1) & (df['name'].isnull())]
        expected = ["Welcome back, there!" for _ in filtered.iterrows()]
        actual = list(filtered['welcome_message'])
        condition = expected == actual
        _dynamic_test(
            self,
            condition,
            "Correct 'Welcome back, there!' for years > 1 and name NULL.",
            "Incorrect 'Welcome back, there!' for years > 1 and name NULL."
        )

    def test_welcome_there(self):
        """Check 'Welcome, there!' is returned for years_at_company <= 1 and name is NULL."""
        # Insert a NULL name row for testing
        self.cursor.execute("INSERT INTO employees (id, name, department, salary, years_at_company) VALUES (101, NULL, 'Test', 50000, 1) ON CONFLICT DO NOTHING;")
        df = self.get_query_result()
        filtered = df[(df['years_at_company'] <= 1) & (df['name'].isnull())]
        expected = ["Welcome, there!" for _ in filtered.iterrows()]
        actual = list(filtered['welcome_message'])
        condition = expected == actual
        _dynamic_test(
            self,
            condition,
            "Correct 'Welcome, there!' for years <= 1 and name NULL.",
            "Incorrect 'Welcome, there!' for years <= 1 and name NULL."
        )

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

def normalize_text(text):
    text = text.lower()
    text = re.sub(r"\\s{2,}", " ", text)
    text = re.sub(r"\\s*([,:?])\\s*", r"\\1 ", text)
    return text.strip()

if __name__ == "__main__":
    unittest.main()


test_solution.py

SQLにおけるCASE WHEN文を基礎的な条件分岐からデータ分析・レポーティングでの高度な活用例まで習得できる包括的なモジュールです。理論と実践的な課題を通じて、複雑なビジネス要件に対応する表現力豊かなクエリの作成方法を学びます。

CASE WHEN文の基本、構文、およびSQLクエリでの単純な条件付きロジックへの活用方法を学習します。

チャレンジ：カスタムウェルカムメッセージ

解答