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()
        # Ensure 'country' table exists and is populated with test data
        cls.cursor.execute("""
            DROP TABLE IF EXISTS country;
        """)
        cls.cursor.execute("""
            CREATE TABLE country (
                id SERIAL PRIMARY KEY,
                capital TEXT
            );
        """)
        # Insert test data (with NULL and normal values)
        cls.cursor.execute("""
            INSERT INTO country (capital) VALUES
                ('Berlin'),
                ('Paris'),
                ('Madrid'),
                ('London'),
                (NULL),
                ('Rome');
        """)
        cls.connection.commit()

    def test_selects_only_capital_column(self):
        """Check if only the 'capital' column is selected from the query result."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        columns = [desc[0] for desc in self.cursor.description]
        condition = columns == ["capital"]
        _dynamic_test(
            self,
            condition,
            "Query selects only the 'capital' column.",
            f"Query should return only the 'capital' column, but got: {columns}"
        )

    def test_uses_country_table_and_all_capitals_included(self):
        """Check if all capitals from country table are included in result (including NULLs if present)."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute("SELECT capital FROM country")
        expected = set(row[0] for row in self.cursor.fetchall())
        self.cursor.execute(query)
        result = set(row[0] for row in self.cursor.fetchall())
        condition = expected == result
        _dynamic_test(
            self,
            condition,
            "All capitals from the country table are included in the result.",
            f"Missing or extra capitals in result. Expected: {expected}, Got: {result}"
        )

    def test_results_sorted_desc_nulls_last(self):
        """Check if the results are sorted by capital in descending order with NULLs last."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        result = [row[0] for row in self.cursor.fetchall()]
        # Find the index where NULL values start
        try:
            first_null_idx = result.index(None)
        except ValueError:
            first_null_idx = len(result)
        non_nulls = result[:first_null_idx]
        nulls = result[first_null_idx:]
        sorted_non_nulls = sorted([x for x in non_nulls if x is not None], reverse=True)
        condition = (
            non_nulls == sorted_non_nulls and
            all(x is None for x in nulls)
        )
        _dynamic_test(
            self,
            condition,
            "Results are sorted by 'capital' in descending order with NULLs last.",
            f"Results are not sorted in descending order with NULLs last: {result}"
        )

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):
    import re
    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

Gain a solid understanding of SQL essentials tailored specifically for business intelligence. You will master querying, filtering, and aggregating business datasets through hands-on tasks designed to mirror real-world professional scenarios.

Challenge: Sort Capitals in Descending Order

Solução