///

Now, imagine that with **many** other **packages** that all your **projects depend on**. That's very difficult to manage. And you would probably end up running some projects with some **incompatible versions** of the packages, and not knowing why something isn't working.

* The same with `app/routers/users.py`, it's another submodule: `app.routers.users`.
* There's also a subdirectory `app/internal/` with another file `__init__.py`, so it's another "Python subpackage": `app.internal`.
* And the file `app/internal/admin.py` is another submodule: `app.internal.admin`.

<img src="/img/tutorial/bigger-applications/package.drawio.svg">

The same file structure with comments:

```
.

        // Test constructor with null message
        PluginException exception = new PluginException(null);

        assertNotNull(exception);
        assertNull(exception.getMessage());
        assertNull(exception.getCause());
    }

    public void test_constructor_withNullMessageAndCause() {
        // Test constructor with null message and null cause

    }

    @Test
    @DisplayName("Test constructor with valid parameters")
    void testConstructor() {
        ValidateNegotiateInfoRequest request =
                new ValidateNegotiateInfoRequest(DEFAULT_CAPABILITIES, defaultClientGuid, DEFAULT_SECURITY_MODE, defaultDialects);

        assertNotNull(request);
    }

    @Test
    @DisplayName("Test size calculation with multiple dialects")
    void testSizeWithMultipleDialects() {

 * It also provides a protected constructor that allows to specify whether or not suppression is enabled or stack trace is writable.
 */
public class CrawlerSystemException extends RuntimeException {

    private static final long serialVersionUID = 1L;

    /**
     * Constructs a new {@code CrawlerSystemException} with the specified detail message and cause.
     *

        // Test constructor with message only
        String message = "SSO login failed";
        SsoLoginException exception = new SsoLoginException(message);

        assertEquals(message, exception.getMessage());
        assertNull(exception.getCause());
    }

    public void test_constructor_withMessageAndCause() {
        // Test constructor with message and cause

/// tip

You can <a href="https://help.github.com/en/github/collaborating-with-issues-and-pull-requests/commenting-on-a-pull-request" class="external-link" target="_blank">add comments with change suggestions</a> to existing pull requests.

/*
 * Copyright 2012-2025 CodeLibs Project and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

/*
 * Copyright 2012-2025 CodeLibs Project and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

/*
 * Copyright 2012-2025 CodeLibs Project and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,