Refactor test file generation and validation logic

This refactor improves maintainability and user experience when generating AI-powered test files.

Author: karangattu

.gitignore

@@ -123,3 +123,4 @@ shiny_bookmarks/
 
 # setuptools_scm
 shiny/_version.py
+shiny/testing/evaluation/apps/*/test_*.py

shiny/_main_generate_test.py

@@ -1,120 +1,145 @@
 from __future__ import annotations
 
+import os
 import sys
 from pathlib import Path
+from typing import Callable
 
 import click
 import questionary
 
 from ._main_utils import cli_action, cli_bold, cli_code, path_rel_wd
 
 
-def generate_test_file(
-    *,
-    app_file: str | None,
-    output_file: str | None,
-    provider: str,
-    model: str | None,
-):
-    """Generate AI-powered test file for a Shiny app."""
-
-    if app_file is None:
-
-        def path_exists(x: str) -> bool | str:
-            if not isinstance(x, (str, Path)):
-                return False
-            path = Path(x)
-            if path.is_dir():
-                return "Please provide a file path to your Shiny app"
-            return path.exists() or f"Shiny app file can not be found: {x}"
-
-        app_file_val = questionary.path(
-            "Enter the path to the app file:",
-            default=path_rel_wd("app.py"),
-            validate=path_exists,
-        ).ask()
-    else:
-        app_file_val = app_file
+class ValidationError(Exception):
+    pass
+
+
+def create_file_validator(
+    file_type: str,
+    must_exist: bool = True,
+    prefix_required: str | None = None,
+    must_not_exist: bool = False,
+) -> Callable[[str], bool | str]:
+    def validator(path_str: str) -> bool | str:
+        if not isinstance(path_str, (str, Path)):
+            return False
+
+        path = Path(path_str)
+
+        if path.is_dir():
+            return f"Please provide a file path for your {file_type}"
+
+        if must_exist and not path.exists():
+            return f"{file_type.title()} file not found: {path_str}"
+
+        if must_not_exist and path.exists():
+            return f"{file_type.title()} file already exists. Please provide a new file name."
+
+        if prefix_required and not path.name.startswith(prefix_required):
+            return f"{file_type.title()} file must start with '{prefix_required}'"
+
+        return True
+
+    return validator
+
+
+def validate_api_key(provider: str) -> None:
+    api_configs = {
+        "anthropic": {
+            "env_var": "ANTHROPIC_API_KEY",
+            "url": "https://console.anthropic.com/",
+        },
+        "openai": {
+            "env_var": "OPENAI_API_KEY",
+            "url": "https://platform.openai.com/api-keys",
+        },
+    }
+
+    if provider not in api_configs:
+        raise ValidationError(f"Unsupported provider: {provider}")
+
+    config = api_configs[provider]
+    if not os.getenv(config["env_var"]):
+        raise ValidationError(
+            f"{config['env_var']} environment variable is not set.\n"
+            f"Please set your {provider.title()} API key:\n"
+            f"  export {config['env_var']}='your-api-key-here'\n\n"
+            f"Get your API key from: {config['url']}"
+        )
+
+
+def get_app_file_path(app_file: str | None) -> Path:
+    if app_file is not None:
+        app_path = Path(app_file)
+        if not app_path.exists():
+            raise ValidationError(f"App file does not exist: {app_path}")
+        return app_path
+    # Interactive mode
+    app_file_val = questionary.path(
+        "Enter the path to the app file:",
+        default=path_rel_wd("app.py"),
+        validate=create_file_validator("Shiny app", must_exist=True),
+    ).ask()
 
     if app_file_val is None:
         sys.exit(1)
 
-    app_path = Path(app_file_val)
+    return Path(app_file_val)
 
-    if not app_path.exists():
-        click.echo(f"❌ Error: App file does not exist: {app_path}")
-        sys.exit(1)
 
-    if output_file is None:
-        suggested_output = app_path.parent / f"test_{app_path.stem}.py"
-
-        def output_path_valid(x: str) -> bool | str:
-            if not isinstance(x, (str, Path)):
-                return False
-            path = Path(x)
-            if path.is_dir():
-                return "Please provide a file path for your test file."
-            if path.exists():
-                return "Test file already exists. Please provide a new file name."
-            if not path.name.startswith("test_"):
-                return "Test file must start with 'test_'"
-            return True
-
-        output_file_val = questionary.path(
-            "Enter the path for the generated test file:",
-            default=str(suggested_output),
-            validate=output_path_valid,
-        ).ask()
-    else:
-        output_file_val = output_file
+def get_output_file_path(output_file: str | None, app_path: Path) -> Path:
+    if output_file is not None:
+        output_path = Path(output_file)
+        if output_path.exists():
+            raise ValidationError(f"Test file already exists: {output_path}")
+        if not output_path.name.startswith("test_"):
+            raise ValidationError("Test file must start with 'test_'")
+        return output_path
+    # Interactive mode
+    suggested_output = app_path.parent / f"test_{app_path.stem}.py"
+
+    output_file_val = questionary.path(
+        "Enter the path for the generated test file:",
+        default=str(suggested_output),
+        validate=create_file_validator(
+            "test", must_exist=False, prefix_required="test_", must_not_exist=True
+        ),
+    ).ask()
 
     if output_file_val is None:
         sys.exit(1)
 
-    output_path = Path(output_file_val)
+    return Path(output_file_val)
 
-    if output_path.exists():
-        click.echo(f"❌ Error: Test file already exists: {output_path}")
-        sys.exit(1)
 
-    if not output_path.name.startswith("test_"):
-        click.echo("❌ Error: Test file must start with 'test_'")
-        sys.exit(1)
+def generate_test_file(
+    *,
+    app_file: str | None,
+    output_file: str | None,
+    provider: str,
+    model: str | None,
+) -> None:
 
     try:
-        from .testing import ShinyTestGenerator
-    except ImportError as e:
-        click.echo(f"❌ Error: Could not import ShinyTestGenerator: {e}")
-        click.echo("Make sure the shiny testing dependencies are installed.")
-        sys.exit(1)
+        validate_api_key(provider)
 
-    import os
-
-    if provider == "anthropic":
-        if not os.getenv("ANTHROPIC_API_KEY"):
-            click.echo("❌ Error: ANTHROPIC_API_KEY environment variable is not set.")
-            click.echo("Please set your Anthropic API key:")
-            click.echo("  export ANTHROPIC_API_KEY='your-api-key-here'")
-            click.echo()
-            click.echo("Get your API key from: https://console.anthropic.com/")
-            sys.exit(1)
-    elif provider == "openai":
-        if not os.getenv("OPENAI_API_KEY"):
-            click.echo("❌ Error: OPENAI_API_KEY environment variable is not set.")
-            click.echo("Please set your OpenAI API key:")
-            click.echo("  export OPENAI_API_KEY='your-api-key-here'")
-            click.echo()
-            click.echo("Get your API key from: https://platform.openai.com/api-keys")
-            sys.exit(1)
-
-    click.echo(f"🤖 Generating test using {provider} provider...")
-    if model:
-        click.echo(f"📝 Using model: {model}")
+        app_path = get_app_file_path(app_file)
+        output_path = get_output_file_path(output_file, app_path)
 
-    try:
-        generator = ShinyTestGenerator(provider=provider)  # type: ignore
+        try:
+            from .testing import ShinyTestGenerator
+        except ImportError as e:
+            raise ValidationError(
+                f"Could not import ShinyTestGenerator: {e}\n"
+                "Make sure the shiny testing dependencies are installed."
+            )
+
+        click.echo(f"🤖 Generating test using {provider} provider...")
+        if model:
+            click.echo(f"📝 Using model: {model}")
 
-        # Generate the test
+        generator = ShinyTestGenerator(provider=provider)  # type: ignore
         _, test_file_path = generator.generate_test_from_file(
             app_file_path=str(app_path),
             model=model,
@@ -129,6 +154,9 @@ def output_path_valid(x: str) -> bool | str:
         )
         click.echo("- Review and customize the test as needed")
 
+    except ValidationError as e:
+        click.echo(f"❌ Error: {e}")
+        sys.exit(1)
     except Exception as e:
         click.echo(f"❌ Error generating test: {e}")
         sys.exit(1)