resolve_fast_api_dependency_manually_for_testing_or_whatever.py

from fastapi import Depends
from fastapi.dependencies.models import Dependant
from fastapi.dependencies.utils import solve_dependencies, get_dependant, get_parameterless_sub_dependant
import asyncio

def resolve_dependency(cls: Type):
    dependant = get_dependant(path="", call=cls)
    dependencies = [
        Depends(cls)
    ]
    for depends in dependencies:
        dependant.dependencies.insert(
            0,
            get_parameterless_sub_dependant(depends=depends, path="something"),
        )

    dependency = solve_dependencies(
        request=Request({"type": "http", "query_string": "", "headers": {}}),
        dependant=dependant,
        body={},
    )
    values, errors, background_tasks, response, dependency_cache = asyncio.run(dependency)
    for key, value in dependency_cache.items():
        type, _ = key
        if type == cls:
            return value

    raise Exception("No found dependency")