n, err := buf.Write(testBytes[0:1])
		if want := 1; err != nil || n != want {
			t.Errorf("Write: got (%d, %v), want (%d, %v)", n, err, want, nil)
		}
		check(t, "TestBasicOperations (4)", &buf, "a")

		buf.WriteByte(testString[1])
		check(t, "TestBasicOperations (5)", &buf, "ab")

		n, err = buf.Write(testBytes[2:26])
		if want := 24; err != nil || n != want {

	for i, v := range vectors {
		r := strings.NewReader(v.in)
		got, err := parsePAX(r)
		if !maps.Equal(got, v.want) && !(len(got) == 0 && len(v.want) == 0) {
			t.Errorf("test %d, parsePAX():\ngot  %v\nwant %v", i, got, v.want)
		}
		if ok := err == nil; ok != v.ok {
			t.Errorf("test %d, parsePAX(): got %v, want %v", i, ok, v.ok)
		}
	}
}

func TestReadOldGNUSparseMap(t *testing.T) {

		if got := IndexRune([]byte(tt.in), tt.rune); got != tt.want {
			t.Errorf("IndexRune(%q, %d) = %v; want %v", tt.in, tt.rune, got, tt.want)
		}
	}

	haystack := []byte("test世界")
	allocs := testing.AllocsPerRun(1000, func() {
		if i := IndexRune(haystack, 's'); i != 2 {
			t.Fatalf("'s' at %d; want 2", i)
		}
		if i := IndexRune(haystack, '世'); i != 4 {
			t.Fatalf("'世' at %d; want 4", i)
		}
	})
	if allocs != 0 {

					}
					path = tf
				}

				want, err := os.ReadFile(path)
				if err != nil {
					t.Fatalf("ReadFile() = %v, want nil", err)
				}
				got := buf.Bytes()
				if !bytes.Equal(want, got) {
					t.Fatalf("incorrect result: (-got +want)\n%v", bytediff(got, want))
				}
			}
		})
	}
}

func TestPax(t *testing.T) {

			printed = f[0] + "\t" + strings.Join(f[1:], " ")
		}

		want := fmt.Sprintf("%05d (%s:%d)\t%s", seq, input, lineno, printed)
		for len(output) > 0 && (output[0] < want || output[0] != want && len(output[0]) >= 5 && output[0][:5] == want[:5]) {
			if len(output[0]) >= 5 && output[0][:5] == want[:5] {
				t.Errorf("mismatched output:\nhave %s\nwant %s", output[0], want)
				output = output[1:]
				continue Diff
			}

But in some cases you need to return a different status code than the default.

## Use case { #use-case }

For example, imagine that you want to return an HTTP status code of "OK" `200` by default.

But if the data didn't exist, you want to create it, and return an HTTP status code of "CREATED" `201`.

But you still want to be able to filter and convert the data you return with a `response_model`.

For those cases, you can use a `Response` parameter.

This means that you can send only the data that you want to update, leaving the rest intact.

/// note

`PATCH` is less commonly used and known than `PUT`.

And many teams use only `PUT`, even for partial updates.

You are **free** to use them however you want, **FastAPI** doesn't impose any restrictions.

But this guide shows you, more or less, how they are intended to be used.

                is not available, instead of erroring out, the dependency result will
                be `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, with OAuth2
                or in a cookie).
                """

                available, instead of erroring out, the dependency result will be
                `None`.

                This is useful when you want to have optional authentication.

                It is also useful when you want to have authentication that can be
                provided in one of multiple optional ways (for example, in a query
                parameter or in an HTTP Bearer token).

# OpenAPI Webhooks { #openapi-webhooks }

There are cases where you want to tell your API **users** that your app could call *their* app (sending a request) with some data, normally to **notify** of some type of **event**.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.