assertEquals("Should be able to peek() at first element", "A", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() first element multiple times", "A", peekingIterator.peek());
    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());

    assertEquals("Should be able to peek() at first element", "A", peekingIterator.peek());
    assertEquals(
        "Should be able to peek() first element multiple times", "A", peekingIterator.peek());
    assertEquals(
        "next() should still return first element after peeking", "A", peekingIterator.next());

    assertEquals("Should be able to peek() at middle element", "B", peekingIterator.peek());

    If you integrate your API with an OAuth2 provider, you will be able to authenticate and come back to the API docs with the acquired credentials. And interact with it using the real OAuth2 authentication.

    Swagger UI will handle it behind the scenes for you, but it needs this "redirect" helper.

### Create a *path operation* to test it

Now, to be able to test that everything works, create a *path operation*:

	if err != nil {
		c.Fatalf("should be able to get user info: %v", err)
	}
	return ui
}

func (c *check) mustNotCreateIAMUser(ctx context.Context, admClnt *madmin.AdminClient) {
	c.Helper()
	randUser := mustGetUUID()
	randPass := mustGetUUID()
	err := admClnt.AddUser(ctx, randUser, randPass)
	if err == nil {
		c.Fatalf("should not be able to create a user")
	}
}

All the dependencies we have seen are a fixed function or class.

But there could be cases where you want to be able to set parameters on the dependency, without having to declare many different functions or classes.

Let's imagine that we want to have a dependency that checks if the query parameter `q` contains some fixed content.

But we want to be able to parameterize that fixed content.

## A "callable" instance

The .mvn directory is needed to be able to use the ${maven.multiModuleProjectDirectory} property....

	if err := DB.Exec(`
CREATE TABLE public.log_usage (
    log_id bigint NOT NULL
);

ALTER TABLE public.log_usage ALTER COLUMN log_id ADD GENERATED BY DEFAULT AS IDENTITY (
    SEQUENCE NAME public.log_usage_log_id_seq
    START WITH 1
    INCREMENT BY 1
    NO MINVALUE
    NO MAXVALUE
    CACHE 1
);
	`).Error; err != nil {
		t.Fatalf("failed to create table, got error %v", err)
	}

This way, if any part of Starlette's internal code, or a Starlette extension or plug-in, raises a Starlette `HTTPException`, your handler will be able to catch and handle it.

In this example, to be able to have both `HTTPException`s in the same code, Starlette's exceptions is renamed to `StarletteHTTPException`:

```Python
from starlette.exceptions import HTTPException as StarletteHTTPException
```

	if err != nil {
		t.Fatalf("Unable to initialize new http request %s", err)
	}
	return req
}

// This is similar to mustNewRequest but additionally the request
// is signed with AWS Signature V4, fails if not able to do so.
func mustNewSignedRequest(method string, urlStr string, contentLength int64, body io.ReadSeeker, t *testing.T) *http.Request {
	req := mustNewRequest(method, urlStr, contentLength, body, t)
	cred := globalActiveCred

   * to timer, and importantly this is the main situation in which we need to be able to see the
   * write.
   *
   * 2. visibility of the writes to an afterDone() call triggered by cancel():
   *
   * Since these fields are non-final that means that TimeoutFuture is not being 'safely published',
   * thus a motivated caller may be able to expose the reference to another thread that would then