python - 如何在 If else 语句上运行 Pytest？

Question

我成功运行了calculate_bmi函数的Pytest，但未能运行bmi_index函数的Pytest。我可以知道如何为 bmi_index 函数运行 Pytest 吗？

def main():
    weight = float(input('Enter weight (kg): '))
    height = float(input('Enter height (cm): '))

    bmi = calculate_bmi(weight, height)
    bmi_index(bmi)
    
def calculate_bmi(weight, height):
    bmi = round(10000 * weight / (height ** 2))
    return bmi

def bmi_index(bmi):
    if bmi <= 18.5:
        print('You are underweight.')
    elif bmi <= 24.9:
        print('You are normal weight.')
    elif bmi <= 29.9:
        print('You are overweight.')
    else: 
        print('You are obese.') 

if __name__ == "__main__":
    main()

我已尝试以下操作，但测试失败(对于 test_bmi_index)。错误是:AssertionError:assert None == '你很肥胖。'我认为这意味着没有要执行的测试，但我不确定如何执行。你能帮我吗？非常感谢。

from practice4 import calculate_bmi, bmi_index
import pytest
from pytest import approx


def test_calculate_bmi():
    """Verify that the calculate bmi function works correctly."""
    assert calculate_bmi(47, 154) == approx(20)
    assert calculate_bmi(-95, 175) == approx(-31)
    assert calculate_bmi(4.5, 1.54) == approx(18975)

def test_bmi_index():
    """Verify that the bmi_index function works correctly."""
    assert bmi_index(31) == 'You are obese.'


pytest.main(["-v", "--tb=line", "-rN", __file__])

========================= test session starts ==========================
platform win32 -- Python 3.9.7, pytest-6.2.5, py-1.11.0, pluggy-1.0.0 -- C:\Users\iamsp\AppData\Local\Programs\Python\Python39\python.exe
cachedir: .pytest_cache
rootdir: C:\Users\iamsp\Documents\Intro To Python Development
collected 2 items

test_practice4.py::test_calculate_bmi PASSED                      [ 50%]
test_practice4.py::test_bmi_index FAILED                          [100%]

=============================== FAILURES ===============================
c:\Users\iamsp\Documents\Intro To Python Development\test_practice4.py:14: AssertionError: assert None == 'You are obese.'
===================== 1 failed, 1 passed in 0.06s ======================
PS C:\Users\iamsp\Documents\Intro To Python Development> 

Answer 1

打印与返回不同。函数 bmi_index 打印文本，但不返回任何内容(因此返回值 None)。您可以通过添加 return 语句来解决此问题:

def bmi_index(bmi):
    if bmi <= 18.5:
        return 'You are underweight.'
    elif bmi <= 24.9:
        return 'You are normal weight.'
    elif bmi <= 29.9:
        return 'You are overweight.'
    else: 
        return 'You are obese.'

或者，如果您愿意的话:

def bmi_index(bmi):
    if bmi <= 18.5:
        print('You are underweight.')
        return 'You are underweight.'
    elif bmi <= 24.9:
        print('You are normal weight.')
        return 'You are normal weight.'
    elif bmi <= 29.9:
        print('You are overweight.')
        return 'You are overweight.'
    else: 
        print('You are obese.')
        return 'You are obese.'