pydantic_ai.models.test

Utility model for quickly testing apps built with PydanticAI.

Here's a minimal example:

test_model_usage.py

from pydantic_ai import Agent
from pydantic_ai.models.test import TestModel

my_agent = Agent('openai:gpt-4o', system_prompt='...')


async def test_my_agent():
    """Unit test for my_agent, to be run by pytest."""
    m = TestModel()
    with my_agent.override(model=m):
        result = await my_agent.run('Testing my agent...')
        assert result.data == 'success (no tool calls)'
    assert m.agent_model_function_tools == []

See Unit testing with TestModel for detailed documentation.

TestModel dataclass

Bases: Model

A model specifically for testing purposes.

This will (by default) call all tools in the agent, then return a tool response if possible, otherwise a plain response.

How useful this model is will vary significantly.

Apart from __init__ derived by the dataclass decorator, all methods are private or match those of the base class.

Source code in pydantic_ai_slim/pydantic_ai/models/test.py

@dataclass
class TestModel(Model):
    """A model specifically for testing purposes.

    This will (by default) call all tools in the agent, then return a tool response if possible,
    otherwise a plain response.

    How useful this model is will vary significantly.

    Apart from `__init__` derived by the `dataclass` decorator, all methods are private or match those
    of the base class.
    """

    # NOTE: Avoid test discovery by pytest.
    __test__ = False

    call_tools: list[str] | Literal['all'] = 'all'
    """List of tools to call. If `'all'`, all tools will be called."""
    custom_result_text: str | None = None
    """If set, this text is return as the final result."""
    custom_result_args: Any | None = None
    """If set, these args will be passed to the result tool."""
    seed: int = 0
    """Seed for generating random data."""
    agent_model_function_tools: list[ToolDefinition] | None = field(default=None, init=False)
    """Definition of function tools passed to the model.

    This is set when the model is called, so will reflect the function tools from the last step of the last run.
    """
    agent_model_allow_text_result: bool | None = field(default=None, init=False)
    """Whether plain text responses from the model are allowed.

    This is set when the model is called, so will reflect the value from the last step of the last run.
    """
    agent_model_result_tools: list[ToolDefinition] | None = field(default=None, init=False)
    """Definition of result tools passed to the model.

    This is set when the model is called, so will reflect the result tools from the last step of the last run.
    """

    async def agent_model(
        self,
        *,
        function_tools: list[ToolDefinition],
        allow_text_result: bool,
        result_tools: list[ToolDefinition],
    ) -> AgentModel:
        self.agent_model_function_tools = function_tools
        self.agent_model_allow_text_result = allow_text_result
        self.agent_model_result_tools = result_tools

        if self.call_tools == 'all':
            tool_calls = [(r.name, r) for r in function_tools]
        else:
            function_tools_lookup = {t.name: t for t in function_tools}
            tools_to_call = (function_tools_lookup[name] for name in self.call_tools)
            tool_calls = [(r.name, r) for r in tools_to_call]

        if self.custom_result_text is not None:
            assert allow_text_result, 'Plain response not allowed, but `custom_result_text` is set.'
            assert self.custom_result_args is None, 'Cannot set both `custom_result_text` and `custom_result_args`.'
            result: _utils.Either[str | None, Any | None] = _utils.Either(left=self.custom_result_text)
        elif self.custom_result_args is not None:
            assert result_tools is not None, 'No result tools provided, but `custom_result_args` is set.'
            result_tool = result_tools[0]

            if k := result_tool.outer_typed_dict_key:
                result = _utils.Either(right={k: self.custom_result_args})
            else:
                result = _utils.Either(right=self.custom_result_args)
        elif allow_text_result:
            result = _utils.Either(left=None)
        elif result_tools:
            result = _utils.Either(right=None)
        else:
            result = _utils.Either(left=None)

        return TestAgentModel(tool_calls, result, result_tools, self.seed)

    def name(self) -> str:
        return 'test-model'

call_tools class-attribute instance-attribute

call_tools: list[str] | Literal['all'] = 'all'

List of tools to call. If 'all', all tools will be called.

custom_result_text class-attribute instance-attribute

custom_result_text: str | None = None

If set, this text is return as the final result.

custom_result_args class-attribute instance-attribute

custom_result_args: Any | None = None

If set, these args will be passed to the result tool.

seed class-attribute instance-attribute

seed: int = 0

Seed for generating random data.

agent_model_function_tools class-attribute instance-attribute

agent_model_function_tools: list[ToolDefinition] | None = (
    field(default=None, init=False)
)

Definition of function tools passed to the model.

This is set when the model is called, so will reflect the function tools from the last step of the last run.

agent_model_allow_text_result class-attribute instance-attribute

agent_model_allow_text_result: bool | None = field(
    default=None, init=False
)

Whether plain text responses from the model are allowed.

This is set when the model is called, so will reflect the value from the last step of the last run.

agent_model_result_tools class-attribute instance-attribute

agent_model_result_tools: list[ToolDefinition] | None = (
    field(default=None, init=False)
)

Definition of result tools passed to the model.

This is set when the model is called, so will reflect the result tools from the last step of the last run.

TestAgentModel dataclass

Bases: AgentModel

Implementation of AgentModel for testing purposes.

Source code in pydantic_ai_slim/pydantic_ai/models/test.py

@dataclass
class TestAgentModel(AgentModel):
    """Implementation of `AgentModel` for testing purposes."""

    # NOTE: Avoid test discovery by pytest.
    __test__ = False

    tool_calls: list[tuple[str, ToolDefinition]]
    # left means the text is plain text; right means it's a function call
    result: _utils.Either[str | None, Any | None]
    result_tools: list[ToolDefinition]
    seed: int

    async def request(
        self, messages: list[ModelMessage], model_settings: ModelSettings | None
    ) -> tuple[ModelResponse, Cost]:
        return self._request(messages, model_settings), Cost()

    @asynccontextmanager
    async def request_stream(
        self, messages: list[ModelMessage], model_settings: ModelSettings | None
    ) -> AsyncIterator[EitherStreamedResponse]:
        msg = self._request(messages, model_settings)
        cost = Cost()

        # TODO: Rework this once we make StreamTextResponse more general
        texts: list[str] = []
        tool_calls: list[ToolCallPart] = []
        for item in msg.parts:
            if isinstance(item, TextPart):
                texts.append(item.content)
            elif isinstance(item, ToolCallPart):
                tool_calls.append(item)
            else:
                assert_never(item)

        if texts:
            yield TestStreamTextResponse('\n\n'.join(texts), cost)
        else:
            yield TestStreamStructuredResponse(msg, cost)

    def gen_tool_args(self, tool_def: ToolDefinition) -> Any:
        return _JsonSchemaTestData(tool_def.parameters_json_schema, self.seed).generate()

    def _request(self, messages: list[ModelMessage], model_settings: ModelSettings | None) -> ModelResponse:
        # if there are tools, the first thing we want to do is call all of them
        if self.tool_calls and not any(isinstance(m, ModelResponse) for m in messages):
            return ModelResponse(
                parts=[ToolCallPart.from_dict(name, self.gen_tool_args(args)) for name, args in self.tool_calls]
            )

        if messages:
            last_message = messages[-1]
            assert isinstance(last_message, ModelRequest), 'Expected last message to be a `ModelRequest`.'

            # check if there are any retry prompts, if so retry them
            new_retry_names = {p.tool_name for p in last_message.parts if isinstance(p, RetryPromptPart)}
            if new_retry_names:
                return ModelResponse(
                    parts=[
                        ToolCallPart.from_dict(name, self.gen_tool_args(args))
                        for name, args in self.tool_calls
                        if name in new_retry_names
                    ]
                )

        if response_text := self.result.left:
            if response_text.value is None:
                # build up details of tool responses
                output: dict[str, Any] = {}
                for message in messages:
                    if isinstance(message, ModelRequest):
                        for part in message.parts:
                            if isinstance(part, ToolReturnPart):
                                output[part.tool_name] = part.content
                if output:
                    return ModelResponse.from_text(pydantic_core.to_json(output).decode())
                else:
                    return ModelResponse.from_text('success (no tool calls)')
            else:
                return ModelResponse.from_text(response_text.value)
        else:
            assert self.result_tools, 'No result tools provided'
            custom_result_args = self.result.right
            result_tool = self.result_tools[self.seed % len(self.result_tools)]
            if custom_result_args is not None:
                return ModelResponse(parts=[ToolCallPart.from_dict(result_tool.name, custom_result_args)])
            else:
                response_args = self.gen_tool_args(result_tool)
                return ModelResponse(parts=[ToolCallPart.from_dict(result_tool.name, response_args)])

TestStreamTextResponse dataclass

Bases: StreamTextResponse

A text response that streams test data.

Source code in pydantic_ai_slim/pydantic_ai/models/test.py

@dataclass
class TestStreamTextResponse(StreamTextResponse):
    """A text response that streams test data."""

    _text: str
    _cost: Cost
    _iter: Iterator[str] = field(init=False)
    _timestamp: datetime = field(default_factory=_utils.now_utc)
    _buffer: list[str] = field(default_factory=list, init=False)

    def __post_init__(self):
        *words, last_word = self._text.split(' ')
        words = [f'{word} ' for word in words]
        words.append(last_word)
        if len(words) == 1 and len(self._text) > 2:
            mid = len(self._text) // 2
            words = [self._text[:mid], self._text[mid:]]
        self._iter = iter(words)

    async def __anext__(self) -> None:
        self._buffer.append(_utils.sync_anext(self._iter))

    def get(self, *, final: bool = False) -> Iterable[str]:
        yield from self._buffer
        self._buffer.clear()

    def cost(self) -> Cost:
        return self._cost

    def timestamp(self) -> datetime:
        return self._timestamp

TestStreamStructuredResponse dataclass

Bases: StreamStructuredResponse

A structured response that streams test data.

Source code in pydantic_ai_slim/pydantic_ai/models/test.py

@dataclass
class TestStreamStructuredResponse(StreamStructuredResponse):
    """A structured response that streams test data."""

    _structured_response: ModelResponse
    _cost: Cost
    _iter: Iterator[None] = field(default_factory=lambda: iter([None]))
    _timestamp: datetime = field(default_factory=_utils.now_utc, init=False)

    async def __anext__(self) -> None:
        return _utils.sync_anext(self._iter)

    def get(self, *, final: bool = False) -> ModelResponse:
        return self._structured_response

    def cost(self) -> Cost:
        return self._cost

    def timestamp(self) -> datetime:
        return self._timestamp