## Starlette functies

**FastAPI** is volledig verenigbaar met (en gebaseerd op) <a href="https://www.starlette.io/" class="external-link" target="_blank"><strong>Starlette</strong></a>.

`FastAPI` is eigenlijk een subklasse van `Starlette`. Dus als je Starlette al kent of gebruikt, zal de meeste functionaliteit op dezelfde manier werken.

* **GraphQL** integratie met <a href="https://strawberry.rocks" class="external-link" target="_blank">Strawberry</a> en andere packages.
* Veel extra functies (dankzij Starlette) zoals:
    * **WebSockets**
    * uiterst gemakkelijke tests gebaseerd op HTTPX en `pytest`
    * **CORS**
    * **Cookie Sessions**
    * ...en meer.

## Prestaties

     *         If all functions return null, the composite function returns null.
     *
     * @throws NullPointerException if the input collection is null or contains null elements.
     */
    static Function<String, String> chain(Collection<? extends Function<String, String>> functions) {
        return s -> {
            for (Function<String, String> function : functions) {
                String v = function.apply(s);

Let's look at how we can make that work.

## pytest.mark.anyio

If we want to call asynchronous functions in our tests, our test functions have to be asynchronous. AnyIO provides a neat plugin for this, that allows us to specify that some test functions are to be called asynchronously.

## HTTPX

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

Let's first focus on the dependency.

It is just a function that can take all the same parameters that a *path operation function* can take:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[8:9] *}

That's it.

**2 lines**.

And it has the same shape and structure that all your *path operation functions* have.

You can think of it as a *path operation function* without the "decorator" (without the `@app.get("/some-path")`).

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import static com.google.common.collect.Maps.transformValues;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import java.util.Map;

/**
 * Tests for {@link Maps#transformValues(Map, Function)}.
 *
 * @author Isaac Shum
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

import static com.google.common.collect.Maps.transformValues;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import java.util.SortedMap;

/**
 * Tests for {@link Maps#transformValues(SortedMap, Function)}.
 *
 * @author Louis Wasserman
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

import static com.google.common.collect.ReflectionFreeAssertThrows.assertThrows;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.testing.MapInterfaceTest;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

### Other utility functions

Any other utility function that you call directly can be created with normal `def` or `async def` and FastAPI won't affect the way you call it.

This is in contrast to the functions that FastAPI calls for you: *path operation functions* and dependencies.