import unittest
import psycopg2
import pandas as pd
import re

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 test_returns_each_product_id(self):
        """Check if query returns each product_id present in sales table."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute("SELECT DISTINCT product_id FROM sales")
        expected_ids = set([row[0] for row in self.cursor.fetchall()])
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        result_ids = set([row[0] for row in rows])
        _dynamic_test(
            self,
            expected_ids == result_ids,
            "Query returns all product_id values from sales table.",
            f"Query does not return all product_id values. Missing: {expected_ids - result_ids}"
        )

    def test_includes_total_quantity_column(self):
        """Check if query includes total_quantity column with correct sums."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute("SELECT product_id, SUM(quantity) AS total_quantity FROM sales GROUP BY product_id")
        expected = dict(self.cursor.fetchall())
        self.cursor.execute(query)
        result = dict(self.cursor.fetchall())
        condition = expected == result
        _dynamic_test(
            self,
            condition,
            "Query includes correct total quantity for each product_id.",
            f"Total quantity values are incorrect. Expected: {expected}, Got: {result}"
        )

    def test_ordered_by_total_quantity_desc(self):
        """Check if results are ordered by total_quantity descending."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        quantities = [row[1] for row in rows]
        condition = quantities == sorted(quantities, reverse=True)
        _dynamic_test(
            self,
            condition,
            "Results are ordered by total_quantity descending.",
            "Results are not ordered by total_quantity in descending order."
        )

    def test_uses_group_by_product_id(self):
        """Check if query uses GROUP BY product_id."""
        with open("query.sql", "r") as file:
            query = file.read()
        uses_group_by = "group by" in normalize_text(query) and "product_id" in normalize_text(query)
        _dynamic_test(
            self,
            uses_group_by,
            "Query uses GROUP BY product_id.",
            "Query does not use GROUP BY product_id."
        )

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

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Challenge: Bestselling Products

Solution

Challenge: Bestselling Products

Solution