# Sub Applications - Mounts { #sub-applications-mounts }

If you need to have two independent FastAPI applications, with their own independent OpenAPI and their own docs UIs, you can have a main app and "mount" one (or more) sub-application(s).

## Mounting a **FastAPI** application { #mounting-a-fastapi-application }

    @Test
    @DisplayName("Should join two elements with delimiter")
    void testJoinTwoElements() {
        String result = StringUtil.join(",", "hello", "world");
        assertEquals("hello,world", result);
    }

    @Test
    @DisplayName("Should join multiple elements with delimiter")
    void testJoinMultipleElements() {
        String result = StringUtil.join(",", "one", "two", "three", "four");

    }

    /**
     * Returns {@literal true} if the two arrays are equal, ignoring the order of elements.
     *
     * @param <T>
     *            the type of the array elements
     * @param array1
     *            the first array
     * @param array2
     *            the second array
     * @return {@literal true} if the two arrays are equal, ignoring the order of elements
     */

   * default rounding mode: if the two nearest representable values are equally near, the one with
   * the least significant bit zero is chosen. (In such cases, both of the nearest representable
   * values are even integers; this method returns the one that is a multiple of a greater power of
   * two.)
   *

    protected T2 second;

    /**
     * Creates and returns a pair of two values.
     *
     * @param <T1>
     *            The type of the first value
     * @param <T2>
     *            The type of the second value
     * @param first
     *            The first value
     * @param second
     *            The second value
     * @return A pair of two values
     */

    }

    @Test
    @DisplayName("Each error code mapping contains exactly two ints")
    void testEachPairLength() {
        for (int i = 0; i < DosError.DOS_ERROR_CODES.length; i++) {
            int[] pair = DosError.DOS_ERROR_CODES[i];
            assertEquals(2, pair.length, String.format("Error mapping at index %d should contain two integers", i));
        }
    }

    @Test

    assertMultimapEquals(ImmutableListMultimap.of("one", 1, "two", 2), "one", 1, "two", 2);
    assertMultimapEquals(
        ImmutableListMultimap.of("one", 1, "two", 2, "three", 3), "one", 1, "two", 2, "three", 3);
    assertMultimapEquals(
        ImmutableListMultimap.of("one", 1, "two", 2, "three", 3, "four", 4),
        "one",
        1,
        "two",
        2,
        "three",
        3,
        "four",

   * their map views, as returned by {@link #asMap}, are also equal.
   *
   * <p>In general, two multimaps with identical key-value mappings may or may not be equal,
   * depending on the implementation. For example, two {@link SetMultimap} instances with the same
   * key-value mappings are equal, but equality of two {@link ListMultimap} instances depends on the

   * safe to do so. The exact circumstances under which a copy will or will not be performed are
   * undocumented and subject to change.
   *
   * @throws IllegalArgumentException if two keys have the same value or two values have the same
   *     key
   * @throws NullPointerException if any key or value in {@code map} is null
   */
  public static <K, V> ImmutableBiMap<K, V> copyOf(Map<? extends K, ? extends V> map) {

        // 1. GIVEN
        KerberosAuthData mockAuthData1 = mock(KerberosAuthData.class);
        KerberosAuthData mockAuthData2 = mock(KerberosAuthData.class);

        // Mock the parse method to return two different objects based on input
        // Must use matchers for all arguments when using any matcher
        mockedStaticAuthData.when(() -> KerberosAuthData.parse(eq(1), eq(new byte[] { 0x01 }), any(Map.class)))