add test for cli - but needs to be improved

tests/test_read_sequence_cli.py

+"""Test Functionality of Read Sequencing CLI.
+
+This test needs to be modified correctly.
+"""
+
+import argparse
+import importlib.util
+import os
+from pathlib import Path
+import sys
+
+import pytest
+
+from src.read_sequencing.cli import (
+    main,
+    parse_args,
+)
+
+PACKAGE_DIR = Path(__file__).resolve().parents[1] / "src/read_sequencing"
+TEST_FILE = Path.cwd() / 'tests/resources/test_terminal_fragments.txt',
+
+
+class TestParseArgs:
+    """Test ``parse_args()`` function."""
+
+    def test_help_option(self, monkeypatch):
+        """Test help option."""
+        monkeypatch.setattr(
+            sys, 'argv', [
+                'htsinfer',
+                '--help',
+            ]
+        )
+        with pytest.raises(SystemExit) as exc:
+            assert parse_args()
+        assert exc.value.code == 0
+
+    def test_one_positional_arg(self, monkeypatch):
+        """Call with one positional arg."""
+        monkeypatch.setattr(
+            sys, 'argv', [
+                str(TEST_FILE),
+            ]
+        )
+        ret_val = parse_args()
+        assert isinstance(ret_val, argparse.Namespace)
+
+    def test_too_many_positional_args(self, monkeypatch):
+        """Call with two positional args."""
+        monkeypatch.setattr(
+            sys, 'argv', [
+                'htsinfer',
+                str(TEST_FILE), str(TEST_FILE),
+            ]
+        )
+        with pytest.raises(SystemExit) as exc:
+            parse_args()
+        assert exc.value.code != 0
+
+
+class TestMain:
+    """Test ``main()`` function."""
+
+    def test_with_too_many_args(self, monkeypatch):
+        """Call with too many positional args."""
+        monkeypatch.setattr(
+            sys, 'argv', [
+                'read_sequencing',
+                str(TEST_FILE), str(TEST_FILE),
+            ]
+        )
+        with pytest.raises(SystemExit) as exc:
+            main()
+        assert exc.value.code != 0
+
+    def test_keyboard_interrupt(self, monkeypatch):
+        """Test keyboard interrupt."""
+
+        class RaiseKeyboardInterrupt:
+            """Helper class to raise `ValueError`."""
+
+            def __init__(self, *args, **kwargs):
+                """Class constructor."""
+                raise KeyboardInterrupt
+
+        monkeypatch.setattr(
+            'src.read_sequencing.cli.parse_args',
+            RaiseKeyboardInterrupt,
+        )
+        with pytest.raises(SystemExit) as exc:
+            main()
+        assert exc.value.code >= 128
+
+
+def test_main_as_script():
+    """Run as script."""
+    main_file = PACKAGE_DIR / "cli.py"
+    fl = os.path.join(os.path.dirname(__file__), main_file)
+    spec = importlib.util.spec_from_file_location('__main__', fl)
+    module = importlib.util.module_from_spec(spec)
+    with pytest.raises(SystemExit) as exc:
+        spec.loader.exec_module(module)  # type: ignore
+    assert exc.value.code != 0