https-deeplearning-ai/generating-cli-tests

Generating CLI Tests

Patterns for generating tests for Typer CLI commands.

Workflow

1. Identify command type (Create/Read/Update/Delete/Bulk)
2. Ensure fixtures exist in conftest.py
3. Write tests using scenarios below
4. Run tests to verify

Fixtures (conftest.py)

import json
import pytest
from typer.testing import CliRunner


@pytest.fixture
def runner():
    """CLI test runner."""
    return CliRunner()


@pytest.fixture
def temp_storage(tmp_path, monkeypatch):
    """Empty storage for testing."""
    storage_dir = tmp_path / ".task"
    storage_dir.mkdir()
    storage_file = storage_dir / "tasks.json"
    storage_file.write_text(json.dumps({"version": 1, "tasks": []}))
    monkeypatch.setenv("TASK_STORAGE_PATH", str(storage_file))
    return storage_file


@pytest.fixture
def sample_data(temp_storage):
    """Pre-populated storage."""
    data = {
        "version": 1,
        "tasks": [
            {"title": "First task", "done": False, "priority": "low", "created_at": "2025-01-01T10:00:00", "due_date": None},
            {"title": "Second task", "done": True, "priority": "high", "created_at": "2025-01-01T11:00:00", "due_date": None},
        ]
    }
    temp_storage.write_text(json.dumps(data))
    return data

Test Structure (AAA)

def test_<command>_<scenario>(runner, temp_storage):
    # Arrange - via fixtures

    # Act
    result = runner.invoke(app, ["<command>", "<args>"])

    # Assert
    assert result.exit_code == 0
    assert "<expected>" in result.output

CliRunner Usage

from typer.testing import CliRunner
from task.main import app

runner = CliRunner()

# Basic
result = runner.invoke(app, ["add", "New task"])

# With options
result = runner.invoke(app, ["add", "Task", "--priority", "high"])

# With confirmation
result = runner.invoke(app, ["clear", "1"], input="y\n")  # Accept
result = runner.invoke(app, ["clear", "1"], input="n\n")  # Decline

# Skip confirmation
result = runner.invoke(app, ["clear", "1", "--force"])

Test Scenarios by Command Type

Create/Add

class TestAdd:
    def test_adds_task(self, runner, temp_storage):
        result = runner.invoke(app, ["add", "New task"])
        assert result.exit_code == 0
        assert "Added" in result.output

    def test_with_priority(self, runner, temp_storage):
        result = runner.invoke(app, ["add", "Task", "--priority", "high"])
        assert result.exit_code == 0

    def test_empty_title_shows_error(self, runner, temp_storage):
        result = runner.invoke(app, ["add", ""])
        assert result.exit_code == 2

Read/List

class TestList:
    def test_shows_tasks(self, runner, sample_data):
        result = runner.invoke(app, ["list"])
        assert result.exit_code == 0
        assert "First task" in result.output

    def test_empty_state(self, runner, temp_storage):
        result = runner.invoke(app, ["list"])
        assert "No tasks" in result.output or "empty" in result.output.lower()

    def test_with_filter(self, runner, sample_data):
        result = runner.invoke(app, ["list", "--done"])
        assert result.exit_code == 0

Update/Done

class TestDone:
    def test_marks_done(self, runner, sample_data):
        result = runner.invoke(app, ["done", "1"])
        assert result.exit_code == 0

    def test_not_found(self, runner, temp_storage):
        result = runner.invoke(app, ["done", "999"])
        assert result.exit_code == 1
        assert "not found" in result.output.lower()

Delete/Clear

class TestClear:
    def test_confirmed(self, runner, sample_data):
        result = runner.invoke(app, ["clear", "1"], input="y\n")
        assert result.exit_code == 0
        assert "Deleted" in result.output

    def test_declined(self, runner, sample_data):
        result = runner.invoke(app, ["clear", "1"], input="n\n")
        assert "Cancelled" in result.output

    def test_force(self, runner, sample_data):
        result = runner.invoke(app, ["clear", "1", "--force"])
        assert result.exit_code == 0

    def test_not_found(self, runner, temp_storage):
        result = runner.invoke(app, ["clear", "999", "--force"])
        assert result.exit_code == 1

Edge Cases to Cover

| Category | Test Cases | |----------|------------| | Invalid Input | Empty string, wrong type, out of range | | Not Found | ID doesn't exist | | Boundary | Zero, negative, first/last item | | State | Already done, empty storage | | Confirmation | Accept (y), decline (n), force flag |

Checklist

• [ ] Test file: tests/test_<command>.py
• [ ] Fixtures in conftest.py
• [ ] Uses CliRunner from typer.testing
• [ ] AAA structure (Arrange, Act, Assert)
• [ ] Tests exit codes: 0, 1, 2
• [ ] Destructive commands: tests y/n and --force
• [ ] Output assertions check expected messages

Running Tests

uv run pytest                       # All tests
uv run pytest -v                    # Verbose
uv run pytest tests/test_add.py    # Specific file