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 test_salary_rank_top3(self):
        """Check only employees with salary_rank 1, 2, or 3 per department are returned."""
        with open("query.sql", "r") as file:
            query = file.read()

        # Execute user query
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        result_df = pd.DataFrame(rows, columns=columns)

        # Calculate expected ranks for each department
        self.cursor.execute("SELECT employee_id, department, salary FROM employees")
        all_emps = pd.DataFrame(self.cursor.fetchall(), columns=["employee_id", "department", "salary"])
        all_emps["salary"] = all_emps["salary"].astype(float)
        all_emps["salary_rank"] = all_emps.groupby("department")['salary'].rank(method="min", ascending=False)
        top3 = all_emps[all_emps["salary_rank"] <= 3]

        # All employee_ids in result must be in top3 per department
        missing = []
        for _, row in result_df.iterrows():
            cond = (
                (top3["employee_id"] == row["employee_id"]) &
                (top3["department"] == row["department"])
            )
            if not cond.any():
                missing.append(dict(row))
        condition = len(missing) == 0
        fail_msg = f"Returned employees not in top 3 salaries per department: {missing}" if missing else ""
        _dynamic_test(self, condition, "All returned employees are in top 3 per department.", fail_msg)

    def test_all_departments_included(self):
        """Check all departments are represented, even if fewer than 3 employees."""
        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]
        result_df = pd.DataFrame(rows, columns=columns)
        self.cursor.execute("SELECT DISTINCT department FROM employees")
        all_depts = set(r[0] for r in self.cursor.fetchall())
        result_depts = set(result_df['department'].unique())
        missing = all_depts - result_depts
        condition = len(missing) == 0
        fail_msg = f"Missing departments in result: {missing}" if missing else ""
        _dynamic_test(self, condition, "All departments are present in the output.", fail_msg)

    def test_output_columns(self):
        """Check output columns are exactly employee_id, name, department, salary."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        columns = [desc[0] for desc in self.cursor.description]
        expected_cols = ["employee_id", "name", "department", "salary"]
        condition = columns == expected_cols
        fail_msg = f"Output columns are {columns}, expected {expected_cols}."
        _dynamic_test(self, condition, "Output columns are correct.", fail_msg)

    def test_output_ordering(self):
        """Check results are ordered by department, salary descending, name."""
        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]
        result_df = pd.DataFrame(rows, columns=columns)
        # Create a sorted version
        sorted_df = result_df.sort_values(["department", "salary", "name"], ascending=[True, False, True]).reset_index(drop=True)
        result_df = result_df.reset_index(drop=True)
        condition = result_df.equals(sorted_df)
        fail_msg = "Rows are not ordered by department, salary descending, then name."
        _dynamic_test(self, condition, "Rows are ordered correctly.", fail_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

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Challenge: Top 3 Salaries per Department

Solution

Challenge: Top 3 Salaries per Department

Solution