import unittest
import psycopg2
import pandas as pd
import re

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_distinct_capital_values(self):
        """Check that only distinct capital values are returned."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        user_rows = self.cursor.fetchall()
        user_capitals = set([row[0] for row in user_rows])
        # Get expected distinct capitals from the table
        self.cursor.execute("SELECT DISTINCT capital FROM country;")
        expected_rows = self.cursor.fetchall()
        expected_capitals = set([row[0] for row in expected_rows])
        condition = user_capitals == expected_capitals
        _dynamic_test(
            self,
            condition,
            "Returned capitals are all unique and match expected distinct values.",
            f"Returned capitals do not match expected distinct values.\\nExpected: {expected_capitals}\\nGot: {user_capitals}"
        )

    def test_no_duplicate_capitals(self):
        """Check that there are no duplicate capital values in the result."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        user_rows = self.cursor.fetchall()
        capitals = [row[0] for row in user_rows]
        condition = len(capitals) == len(set(capitals))
        _dynamic_test(
            self,
            condition,
            "There are no duplicate capital values in the result.",
            "Duplicate capital values found in the result."
        )

    def test_column_name(self):
        """Check that the column name in the result is 'capital'."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        colnames = [desc[0] for desc in self.cursor.description]
        condition = len(colnames) == 1 and normalize_text(colnames[0]) == "capital"
        _dynamic_test(
            self,
            condition,
            "Result column name is 'capital'.",
            f"Result column name is not 'capital'. Got: {colnames}"
        )

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 Country Capitals

Solution