import pytest
from src.masterdata.service import calculate_pmt

def test_calculate_pmt_zero_rate():
    # PMT = -PV / nper when rate is 0
    pv = 1000
    nper = 10
    rate = 0
    result = calculate_pmt(rate, nper, pv)
    assert result == -100

def test_calculate_pmt_standard():
    # Example: Loan 1000, 5% rate, 2 periods
    # PMT = -1000 * (0.05 * (1.05)^2) / ((1.05)^2 - 1)
    # PMT = -1000 * (0.05 * 1.1025) / (0.1025)
    # PMT = -1000 * (0.055125) / (0.1025) = -537.8048...
    result = calculate_pmt(5, 2, 1000)
    assert round(result, 2) == -537.80

def test_calculate_pmt_percentage():
    # If rate > 1, it divides by 100
    result_5 = calculate_pmt(5, 10, 1000)
    result_05 = calculate_pmt(0.05, 10, 1000)
    assert result_5 == result_05