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Validating Event System and Component Interactions in gradio-app

This test suite validates event handling and component interactions in the Gradio framework, focusing on event listeners, chaining, and component state management. It ensures proper event propagation and handling across different UI components.

Test Coverage Overview

The test suite provides comprehensive coverage of Gradio’s event system:

Event clearing and handling for Image components
Event data processing and validation
Consecutive event chaining and dependencies
Event listener registration and triggers
Load event chaining and component state management

Implementation Analysis

The testing approach uses pytest fixtures and isolated test cases to verify event behavior. It implements mock components and event handlers to validate event propagation, with particular attention to the Blocks API and component interactions.

Key patterns include dependency validation, event chaining verification, and state management testing.

Technical Details

Testing tools and configuration:

pytest for test framework
FastAPI TestClient for API testing
Custom event handlers and mock components
Gradio Blocks API for component management
AST parsing for interface validation

Best Practices Demonstrated

The test suite exemplifies strong testing practices:

Isolated test cases for specific functionality
Comprehensive error case coverage
Interface consistency validation
Clear test organization and naming
Proper setup and teardown management

gradio-app/gradio

test/test_events.py

            
import ast
import inspect
from pathlib import Path

import pytest
from fastapi.testclient import TestClient

import gradio as gr


class TestEvent:
    def test_clear_event(self):
        def fn_img_cleared():
            print("image cleared")

        with gr.Blocks() as demo:
            img = gr.Image(
                type="pil", label="Start by uploading an image", elem_id="input_image"
            )

            img.clear(fn_img_cleared, [], [])

        assert "dependencies" in demo.config
        assert demo.config["dependencies"][0]["targets"][0][1] == "clear"

    def test_event_data(self):
        with gr.Blocks() as demo:
            text = gr.Textbox()
            gallery = gr.Gallery()

            def fn_img_index(evt: gr.SelectData):
                return evt.index

            gallery.select(fn_img_index, None, text)

        app, _, _ = demo.launch(prevent_thread_lock=True)
        client = TestClient(app)

        resp = client.post(
            f"{demo.local_api_url}run/predict",
            json={"fn_index": 0, "data": [], "event_data": {"index": 1, "value": None}},
        )
        assert resp.status_code == 200
        assert resp.json()["data"][0] == "1"

    def test_consecutive_events(self):
        def double(x):
            return x + x

        def reverse(x):
            return x[::-1]

        def clear():
            return ""

        with gr.Blocks() as child:
            txt1 = gr.Textbox()
            txt2 = gr.Textbox()
            txt3 = gr.Textbox()

            txt1.submit(double, txt1, txt2).then(reverse, txt2, txt3).success(
                clear, None, txt1
            )

        with gr.Blocks() as parent:
            txt0 = gr.Textbox()
            txt0.submit(lambda x: x, txt0, txt0)
            child.render()

        assert "dependencies" in parent.config
        assert parent.config["dependencies"][1]["trigger_after"] is None
        assert parent.config["dependencies"][2]["trigger_after"] == 1
        assert parent.config["dependencies"][3]["trigger_after"] == 2

        assert not parent.config["dependencies"][2]["trigger_only_on_success"]
        assert parent.config["dependencies"][3]["trigger_only_on_success"]

    def test_on_listener(self):
        with gr.Blocks() as demo:
            name = gr.Textbox(label="Name")
            output = gr.Textbox(label="Output Box")
            greet_btn = gr.Button("Greet")

            def greet(name):
                return "Hello " + name + "!"

            gr.on(
                triggers=[name.submit, greet_btn.click, demo.load],
                fn=greet,
                inputs=name,
                outputs=output,
            )

            with gr.Row():
                num1 = gr.Slider(1, 10)
                num2 = gr.Slider(1, 10)
                num3 = gr.Slider(1, 10)
            output = gr.Number(label="Sum")

            @gr.on(inputs=[num1, num2, num3], outputs=output)
            def sum(a, b, c):
                return a + b + c

        assert "dependencies" in demo.config
        assert demo.config["dependencies"][0]["targets"] == [
            (name._id, "submit"),
            (greet_btn._id, "click"),
            (demo._id, "load"),
        ]
        assert demo.config["dependencies"][1]["targets"] == [
            (num1._id, "change"),
            (num2._id, "change"),
            (num3._id, "change"),
            (0, "load"),
        ]

    def test_load_chaining(self):
        calls = 0

        def increment():
            nonlocal calls
            calls += 1
            return str(calls)

        with gr.Blocks() as demo:
            out = gr.Textbox(label="Call counter")
            demo.load(increment, inputs=None, outputs=out).then(
                increment, inputs=None, outputs=out
            )

        assert "dependencies" in demo.config
        assert demo.config["dependencies"][0]["targets"][0][1] == "load"
        assert demo.config["dependencies"][0]["trigger_after"] is None
        assert demo.config["dependencies"][1]["targets"][0][1] == "then"
        assert demo.config["dependencies"][1]["trigger_after"] == 0

    def test_load_chaining_reuse(self):
        calls = 0

        def increment():
            nonlocal calls
            calls += 1
            return str(calls)

        with gr.Blocks() as demo:
            out = gr.Textbox(label="Call counter")
            demo.load(increment, inputs=None, outputs=out).then(
                increment, inputs=None, outputs=out
            )

        with gr.Blocks() as demo2:
            demo.render()
        assert "dependencies" in demo2.config
        assert demo2.config["dependencies"][0]["targets"][0][1] == "load"
        assert demo2.config["dependencies"][0]["trigger_after"] is None
        assert demo2.config["dependencies"][1]["targets"][0][1] == "then"
        assert demo2.config["dependencies"][1]["trigger_after"] == 0


class TestEventErrors:
    def test_event_defined_invalid_scope(self):
        with gr.Blocks() as demo:
            textbox = gr.Textbox()
            textbox.blur(lambda x: x + x, textbox, textbox)

        with pytest.raises(AttributeError):
            demo.load(lambda: "hello", None, textbox)

        with pytest.raises(AttributeError):
            textbox.change(lambda x: x + x, textbox, textbox)


def test_event_pyi_file_matches_source_code():
    """Test that the template used to create pyi files (search INTERFACE_TEMPLATE in component_meta) matches the source code of EventListener._setup."""
    code = (
        Path(__file__).parent / ".." / "gradio" / "components" / "button.pyi"
    ).read_text()
    mod = ast.parse(code)
    segment = None
    for node in ast.walk(mod):
        if isinstance(node, ast.FunctionDef) and node.name == "click":
            segment = ast.get_source_segment(code, node)

    # This would fail if Button no longer has a click method
    assert segment
    sig = inspect.signature(gr.Button.click)
    for param in sig.parameters.values():
        if param.name in ["block", "time_limit", "stream_every", "like_user_message"]:
            continue
        assert param.name in segment

    code = (
        Path(__file__).parent / ".." / "gradio" / "components" / "image.pyi"
    ).read_text()
    mod = ast.parse(code)
    segment = None
    for node in ast.walk(mod):
        if isinstance(node, ast.FunctionDef) and node.name == "stream":
            segment = ast.get_source_segment(code, node)

    # This would fail if Image no longer has a stream method
    assert segment
    sig = inspect.signature(gr.Image.stream)
    for param in ["time_limit", "stream_every"]:
        assert param in segment