# test_app.py
import gradio as gr

def hello(name):
    return f"Hello {name}!"

with gr.Blocks() as demo:
    inp = gr.Textbox(placeholder="Name")
    out = gr.Textbox()
    gr.Button("Say hi").click(fn=hello, inputs=inp, outputs=out)

if __name__ == "__main__":
    demo.launch()