How can I create a node in a PHPUnit Test without having to create the node type in PHPUnit
When you create a node, you need to reference a bundle that already exists. In your case, you are referencing a bundle (expense) that is created from a custom module, but that module is not installed.

If you look at the tests for the Node module, you will notice they always install the Node module. In the test classes that expand the NodeTestBase class, that is done from that class. In other test classes, for example the NodeFieldAccessTest class (a Kernel test), that is done directly by that test class.  

In your case, changing the list of modules to install to the following one would solve the issue.

  /**
   * Modules to enable.
   *
   * @var array
   */
  public static $modules = ['node', 'paragraphs', 'my_module'];


From the error messages, I take the machine name of the module creating the content type is my_module. If that is not correct, replace my_module with the correct machine name.