import unittest
import psycopg2
import pandas as pd

class TestTask(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 test_unique_continents_and_order(self):
        """Check that the query returns all unique continents in ascending order."""
        with open("query.sql", "r") as file:
            query = file.read()

        # Reference solution
        solution_query = """
            SELECT DISTINCT continent FROM country ORDER BY continent;
        """
        self.cursor.execute(solution_query)
        expected_rows = self.cursor.fetchall()
        expected_continents = [row[0] for row in expected_rows]

        # User query
        self.cursor.execute(query)
        user_rows = self.cursor.fetchall()
        user_continents = [row[0] for row in user_rows]

        # Check all expected continents are present
        condition_all_present = user_continents == expected_continents
        if not condition_all_present:
            failure_msg = (
                f"Expected continents in ascending order: {expected_continents}, "
                f"but got: {user_continents}."
            )
        else:
            failure_msg = ""
        _dynamic_test(
            self,
            condition_all_present,
            "Returned all unique continents in ascending order.",
            failure_msg
        )

    def test_no_duplicates(self):
        """Check that there are no duplicate continents in the result."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        continents = [row[0] for row in rows]
        unique_continents = set(continents)
        condition_no_duplicates = len(continents) == len(unique_continents)
        if not condition_no_duplicates:
            failure_msg = (
                f"Duplicate continents found in result: {continents}"
            )
        else:
            failure_msg = ""
        _dynamic_test(
            self,
            condition_no_duplicates,
            "No duplicate continents in the result.",
            failure_msg
        )

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

Focuses on practical SQL skills for filtering data with WHERE, sorting results with ORDER BY, and summarizing information using GROUP BY and aggregate functions. Hands-on challenges reinforce each concept, preparing learners to analyze and summarize real-world datasets effectively.

Challenge: Find All Continents and Sort Them in Ascending Order

Solution