对具有互斥参数的CLI程序的测试将抛出SystemExit而不是预期的ValueError

Question

我有一个命令行应用程序，它可以接受命令行参数--input_files或--unigrams，但不能同时接受两者：

import click
import pathlib
from typing import Optional

@click.command()
@click.option(
    "--input_files",
    default=None,
    type=str,
    help="Comma-separated list of one-sentence-per-line raw corpus files",
)
@click.option("--unigrams", default=None, type=str, help="Comma-separated list of unigrams")
@click.option(
    "--model_path",
    default="spm/models",
    type=click.Path(file_okay=False, path_type=pathlib.Path),
    help="Output model path",
)
def minimal(
    model_path: pathlib.Path,
    input_files: Optional[str],
    unigrams: Optional[str]
) -> str:
    if input_files and unigrams:
        raise ValueError("Only one of input_files or unigrams can be specified.")

    if input_files:
        click.echo(f"input_files: {input_files}")

    if unigrams:
        click.echo(f"Unigrams: {unigrams}")

我编写了一个测试，用于使用文件系统隔离传递两个参数的情况，并期望引发ValueError：

from click.testing import CliRunner

def test_minimal(tmp_path: str) -> None:
    runner = CliRunner()
    with runner.isolated_filesystem(temp_dir=tmp_path):
        result = runner.invoke(
            minimal,
            ["--model_path", tmp_path, "--input-files", "test.txt", "--unigrams", "a,b"],
        )
        assert isinstance(result.exception, ValueError)
        assert "Only one of input_files or unigrams can be specified." in str(result.exception)

但是，由于引发了SystemExit，此测试失败：

=================================================================================== FAILURES ====================================================================================
_________________________________________________________________________________ test_minimal __________________________________________________________________________________

tmp_path = PosixPath('/tmp/pytest-of-biogeek/pytest-2/test_minimal0')

    def test_minimal(tmp_path: str) -> None:
        runner = CliRunner()
        with runner.isolated_filesystem(temp_dir=tmp_path):
            result = runner.invoke(
                train_spm.minimal,
                ["--model_path", tmp_path, "--input-files", "test.txt", "--unigrams", "a,b"],
            )
>           assert isinstance(result.exception, ValueError)
E           assert False
E            +  where False = isinstance(SystemExit(2), ValueError)
E            +    where SystemExit(2) = <Result SystemExit(2)>.exception

stackoverflow_test.py:20: AssertionError
============================================================================ short test summary info ============================================================================
FAILED projects/stackoverflow_test.py::test_minimal - assert False

我做错了什么？

Answer 1

SystemExit(2)是这个答案引用的UsageError。这意味着命令行脚本中可能有不正确的地方。

在检查原始文件时，可以将参数标志定义为--input_files。但是，测试脚本正在调用--input-files。

用下划线代替破折号可以解决问题，并通过测试。