## Description from docstring { #description-from-docstring }

As descriptions tend to be long and cover multiple lines, you can declare the *path operation* description in the function <abbr title="a multi-line string as the first expression inside a function (not assigned to any variable) used for documentation">docstring</abbr> and **FastAPI** will read it from there.

        final String docString = getXmlString(document);
        final String pnString = getXmlString(pruneNode);
        assertTrue(docString.contains("<SCRIPT>"));
        assertTrue(docString.contains("foo"));
        assertTrue(docString.contains("<NOSCRIPT>"));
        assertTrue(docString.contains("bar"));
        assertTrue(pnString.contains("<SCRIPT>"));

{* ../../docs_src/path_operation_advanced_configuration/tutorial003.py hl[6] *}

## Advanced description from docstring { #advanced-description-from-docstring }

You can limit the lines used from the docstring of a *path operation function* for OpenAPI.

Adding an `\f` (an escaped "form feed" character) causes **FastAPI** to truncate the output used for OpenAPI at this point.

It is a plug-in for many frameworks (and there's a plug-in for Starlette too).

The way it works is that you write the definition of the schema using YAML format inside the docstring of each function handling a route.

And it generates OpenAPI schemas.

That's how it works in Flask, Starlette, Responder, etc.

* Add support for truncating docstrings from *path operation functions*.
    * New docs at [Advanced description from docstring](https://fastapi.tiangolo.com/advanced/path-operation-advanced-configuration/#advanced-description-from-docstring).
    * PR [#556](https://github.com/tiangolo/fastapi/pull/556) by [@svalouch](https://github.com/svalouch).

    }

    @Nested
    @DisplayName("toString() Tests")
    class ToStringTests {

        @Test
        @DisplayName("toString with valid data produces expected format")
        void testToStringWithValidData() {
            byte[] challenge = new byte[] { (byte) 0x01, (byte) 0x02, (byte) 0x03, (byte) 0xFF };
            UniAddress dc = mock(UniAddress.class);
            when(dc.toString()).thenReturn("SERVER123");

        short maxLength = 20;
        int pointer = 100;
        PacUnicodeString pacString = new PacUnicodeString(length, maxLength, pointer);

        // Verify that the object was created
        assertNotNull(pacString, "The PacUnicodeString object should not be null.");

        // Verify that the getters return the correct values
        assertEquals(length, pacString.getLength(), "The length should match the value provided in the constructor.");

        // Test toString with empty string and zterm = true
        UnicodeString emptyUnicodeStringTrue = new UnicodeString("", true);
        assertEquals("", emptyUnicodeStringTrue.toString(), "toString should return empty string for empty input with zterm");

        // Test toString with empty string and zterm = false

        assertEquals(info1.toString(), info2.toString());
    }

    @Test
    @DisplayName("Test encode does not modify source object")
    void testEncodeImmutability() {
        long originalValue = 1000L;
        FileEndOfFileInformation info = new FileEndOfFileInformation(originalValue);

        // Get original toString
        String originalString = info.toString();

        // Encode

        assertNull(ex.getCause());

        // Assert - toString starts with class name and contains message when present
        if (message == null) {
            assertEquals(SMBProtocolDowngradeException.class.getName(), ex.toString());
        } else if (message.isEmpty()) {
            // Throwable.toString prints class + ": " (with space) even for empty string