## Pin your `fastapi` version { #pin-your-fastapi-version }

The first thing you should do is to "pin" the version of **FastAPI** you are using to the specific latest version that you know works correctly for your application.

For example, let's say you are using version `0.112.0` in your app.

You will see the automatic API docs for the sub-application, including only its own _path operations_, all under the correct sub-path prefix `/subapi`:

<img src="/img/tutorial/sub-applications/image02.png">

If you try interacting with any of the two user interfaces, they will work correctly, because the browser will be able to talk to each specific app or sub-app.

### Technical Details: `root_path` { #technical-details-root-path }

        }

        @Test
        @DisplayName("Should handle offset correctly")
        void testSignWithOffset() {
            byte[] largeData = new byte[256];
            int offset = 64;
            Arrays.fill(largeData, (byte) 0x00);

            digest.sign(largeData, offset, 128, request, response);

            // Verify signature is placed at correct location

        assertTrue(exception.getMessage().contains("DISK_FULL"));
        assertTrue(exception.getMessage().contains("Disk full"));
    }

    @Test
    @DisplayName("Should have correct retryable flags for error codes")
    void testErrorCodeRetryableFlags() {
        // Retryable errors
        assertTrue(SmbOperationException.ErrorCode.CONNECTION_FAILED.isRetryable());

If you added the return type annotation, tools and editors would complain with a (correct) error telling you that your function is returning a type (e.g. a dict) that is different from what you declared (e.g. a Pydantic model).

And open the docs at <a href="http://127.0.0.1:8000/docs" class="external-link" target="_blank">http://127.0.0.1:8000/docs</a>.

You will see the automatic API docs, including the paths from all the submodules, using the correct paths (and prefixes) and the correct tags:

<img src="/img/tutorial/bigger-applications/image01.png">

## Include the same router multiple times with different `prefix` { #include-the-same-router-multiple-times-with-different-prefix }

        // Then
        assertNotNull(resp);
        assertTrue(resp instanceof ServerMessageBlock2Response);
        assertTrue(resp instanceof ServerMessageBlock2);
    }

    @Test
    @DisplayName("Should return correct OVERHEAD constant value")
    void testOverheadConstant() {
        // Then
        assertEquals(Smb2Constants.SMB2_HEADER_LENGTH + 16, Smb2ReadResponse.OVERHEAD);
    }

    @Test

    }

    @Test
    @DisplayName("Should return correct cipher ID")
    void testGetCipherId() {
        // When
        int cipherId = encryptionContext.getCipherId();

        // Then
        assertEquals(1, cipherId, "Should return the cipher ID set in constructor");
    }

    @Test
    @DisplayName("Should return correct dialect version")
    void testGetDialect() {
        // When

    Note over Server: Server interprets headers<br/>(if --forwarded-allow-ips is set)

    Server->>Proxy: HTTP Response<br/>with correct HTTPS URLs

    Proxy->>Client: HTTPS Response
```

The **proxy** intercepts the original client request and adds the special *forwarded* headers (`X-Forwarded-*`) before passing the request to the **application server**.

        assertEquals(SmbComTransaction.TRANSACTION_BUF_SIZE, buffer2.length, "Reused buffer should have correct size");

        // Note: We don't check if content is cleared as that's not a security requirement
        // The important part is that the buffer is valid and has correct size
    }

    /**
     * Test getBuffers method for transaction buffers.
     */
    @Test