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_row_count_matches_performance(self):
        """Returns a row for every performance review in the performance table."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute("SELECT COUNT(*) FROM performance;")
        expected_count = self.cursor.fetchone()[0]
        self.cursor.execute(query)
        actual_count = len(self.cursor.fetchall())
        _dynamic_test(
            self,
            actual_count == expected_count,
            f"Returned {actual_count} rows, matching performance table.",
            f"Returned {actual_count} rows, but performance table has {expected_count} rows."
        )

    def test_columns_present(self):
        """Includes columns: employee_id, name, review_date, score, and score_difference."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute(query)
        columns = [desc[0] for desc in self.cursor.description]
        expected = {"employee_id", "name", "review_date", "score", "score_difference"}
        condition = expected.issubset(set(columns))
        _dynamic_test(
            self,
            condition,
            "All required columns are present.",
            f"Missing columns: {expected - set(columns)}"
        )

    def test_score_difference_logic(self):
        """For each employee, score_difference is the difference between current and previous review score, ordered by review_date. First review is NULL."""
        with open("query.sql", "r") as file:
            query = file.read()
        # Get expected data
        self.cursor.execute("SELECT employee_id, review_date, score FROM performance ORDER BY employee_id, review_date;")
        perf = self.cursor.fetchall()
        expected = []
        from collections import defaultdict
        by_emp = defaultdict(list)
        for eid, date, score in perf:
            by_emp[eid].append((date, score))
        for eid in sorted(by_emp.keys()):
            reviews = sorted(by_emp[eid], key=lambda x: x[0])
            last = None
            for date, score in reviews:
                if last is None:
                    expected.append((eid, date, score, None))
                else:
                    expected.append((eid, date, score, score - last))
                last = score
        # Query user's result
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        # Map by employee_id and review_date
        idx_eid = columns.index("employee_id")
        idx_date = columns.index("review_date")
        idx_score = columns.index("score")
        idx_diff = columns.index("score_difference")
        result_map = {(r[idx_eid], r[idx_date]): (r[idx_score], r[idx_diff]) for r in rows}
        failed = []
        for eid, date, score, diff in expected:
            if (eid, date) not in result_map:
                failed.append(f"Missing row for employee {eid} on {date}")
                continue
            user_score, user_diff = result_map[(eid, date)]
            if user_score != score:
                failed.append(f"Wrong score for employee {eid} on {date}: got {user_score}, expected {score}")
            # Accept None or NULL for first diff
            if diff is None:
                if user_diff is not None:
                    failed.append(f"score_difference for employee {eid} on {date} should be NULL, got {user_diff}")
            else:
                if user_diff != diff:
                    failed.append(f"score_difference for employee {eid} on {date}: got {user_diff}, expected {diff}")
        _dynamic_test(
            self,
            len(failed) == 0,
            "score_difference is correct for all employees and reviews.",
            "\\n".join(failed)
        )

    def test_ordering(self):
        """Results are ordered by employee_id and review_date."""
        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]
        idx_eid = columns.index("employee_id")
        idx_date = columns.index("review_date")
        ordered = True
        last = None
        for row in rows:
            key = (row[idx_eid], row[idx_date])
            if last is not None:
                if key < last:
                    ordered = False
                    break
            last = key
        _dynamic_test(
            self,
            ordered,
            "Rows are ordered by employee_id and review_date.",
            "Rows are not ordered by employee_id and review_date."
        )

    def test_name_is_correct(self):
        """name column matches employees table for each employee_id."""
        with open("query.sql", "r") as file:
            query = file.read()
        self.cursor.execute("SELECT employee_id, name FROM employees;")
        emp_map = dict(self.cursor.fetchall())
        self.cursor.execute(query)
        rows = self.cursor.fetchall()
        columns = [desc[0] for desc in self.cursor.description]
        idx_eid = columns.index("employee_id")
        idx_name = columns.index("name")
        fail = []
        for row in rows:
            eid = row[idx_eid]
            name = row[idx_name]
            if eid not in emp_map or emp_map[eid] != name:
                fail.append(f"name for employee_id {eid} should be '{emp_map.get(eid)}', got '{name}'")
        _dynamic_test(
            self,
            len(fail) == 0,
            "name column matches employees table for each employee_id.",
            "\\n".join(fail)
        )

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: Compare Performance Over Time

Solution

Challenge: Compare Performance Over Time

Solution