# Test Client - `TestClient`

You can use the `TestClient` class to test FastAPI applications without creating an actual HTTP and socket connection, just communicating directly with the FastAPI code.

Read more about it in the [FastAPI docs for Testing](https://fastapi.tiangolo.com/tutorial/testing/).

You can import it directly from `fastapi.testclient`:

```python
from fastapi.testclient import TestClient
```

app = FastAPI()


def magic_data_reader(raw_body: bytes):
    return {
        "size": len(raw_body),
        "content": {
            "name": "Maaaagic",
            "price": 42,
            "description": "Just kiddin', no magic here. ✨",
        },
    }


@app.post(
    "/items/",
    openapi_extra={
        "requestBody": {
            "content": {
                "application/json": {

                }
            } catch( Exception ex ) {
                String msg = ex.getMessage();
                boolean timeout = msg != null && msg.equals( "Read timed out" );
                /* If just a timeout, try to disconnect gracefully
                 */
                boolean hard = timeout == false;

                if (!timeout && log.level >= 3)
                    ex.printStackTrace( log );

type ControlPlaneOptions struct {
	// Revision is the istio.io/rev control plane revision
	Revision string
}

// AttachControlPlaneFlags attaches control-plane flags to a Cobra command.
// (Currently just --revision)
func (o *ControlPlaneOptions) AttachControlPlaneFlags(cmd *cobra.Command) {
	cmd.PersistentFlags().StringVarP(&o.Revision, "revision", "r", "",
		"Control plane revision")

    // These contain bytes not in the decodabet.
    assertFailsToDecode(base64(), "A\u007f", "Unrecognized character: 0x7f");
    assertFailsToDecode(base64(), "Wf2!", "Unrecognized character: !");
    // This sentence just isn't base64() encoded.
    assertFailsToDecode(base64(), "let's not talk of love or chains!");
    // A 4n+1 length string is never legal base64().
    assertFailsToDecode(base64(), "12345", "Invalid input length 5");

 *
 * <ul>
 *   <li>An annotation named just "Suppress" might someday be treated by a non-Android tool as a
 *       suppression. This would follow the precedent of many of our annotation processors, which
 *       look for any annotation named, e.g., "GwtIncompatible," regardless of package.
 *   <li>An annotation named just "Suppress" might suggest to users that the test is suppressed

// the text of the most recently returned token is, and where it was found.
// The underlying scanner elides all spaces except newline, so the input looks like a stream of
// Tokens; original spacing is lost but we don't need it.
type TokenReader interface {
	// Next returns the next token.
	Next() ScanToken
	// The following methods all refer to the most recent token returned by Next.

    id: context
    attributes:
      label: Context (optional)
      description: |
        How has this issue affected you? What are you trying to accomplish?
        Providing context helps us come up with a solution that is most useful in the real world
    validations:

this is just a marker file....

    // https://github.com/google/guava/issues/2996
    // no data, just testing that there's no StackOverflowException
    assertEquals(-1, tenMillionEmptySources().read());
  }

  public void testReadArray_noStackOverflow() throws IOException {
    // https://github.com/google/guava/issues/2996
    // no data, just testing that there's no StackOverflowException