Improve integration tests assertions for docling

[apupier]

Several tests were checking only that the result was not null and empty. Now checking some subparts of expected result and the file type.

Description

Target

• I checked that the commit is targeting the correct branch (Camel 4 uses the main branch)

Tracking

• If this is a large change, bug fix, or code improvement, I checked there is a JIRA issue filed for the change (usually before you start working on it).

Apache Camel coding standards and style

• I checked that each commit in the pull request has a meaningful subject line and body.

• I have run mvn clean install -DskipTests locally from root folder and I have committed all auto-generated changes.

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[squakez]

LGTM, but, out of curiosity? why are you removing the public modifier?

[apupier]

why are you removing the public modifier?

Since JUnit 5, the public modifier is no more required and even recommended to be omited https://docs.junit.org/5.13.0-M2/user-guide/index.html#writing-tests-classes-and-methods

There is also a Sonar rule https://rules.sonarsource.com/java/quickfix/RSPEC-5786/