Add some hints on test tooling (#7585)

* Add some hints on test tooling

* Fix comments

docs/getting-into-the-code/code-howtos.md

@@ -229,6 +229,8 @@ Defaults should go into the model package. See [Comments in this Commit](https:/
 
 ## Test Cases
 
+### General hints on tests
+
 Imagine you want to test the method `format(String value)` in the class `BracesFormatter` which removes double braces in a given string.
 
 * _Placing:_ all tests should be placed in a class named `classTest`, e.g. `BracesFormatterTest`.
@@ -316,6 +318,22 @@ public void getTypeReturnsBibLatexArticleInBibLatexMode() {
 
 To test that a preferences migration works successfully, use the mockito method `verify`. See `PreferencesMigrationsTest` for an example.
 
+### Background on Java testing
+
+In JabRef, we mainly rely to basic JUnit tests to increase code coverage.
+There are other ways to test:
+
+| Type | Techniques | Tool (Java) | Kind of tests | Used In JabRef |
+| -- | -- | -- | -- | -- |
+| Functional | Dynamics, black box, positive and negative | [JUnit-QuickCheck](https://github.com/pholser/junit-quickcheck) | Random data generation | No, not intended, because other test kinds seem more helpful. |
+| Functional | Dynamics, black box, positive and negative | [GraphWalker](https://graphwalker.github.io/) | Model-based | No, because the BibDatabase doesn't need to be tests |
+| Functional | Dynamics, black box, positive and negative | [TestFX](https://github.com/TestFX/TestFX) | GUI Tests | Yes |
+| Functional | Dynamics, white box, negative | [PIT](https://pitest.org/) | Mutation | No |
+| Functional | Dynamics, white box, positive and negative | [Mockito](https://site.mockito.org/) | Mocking | Yes |
+| Non-functional | Dynamics, black box, positive and negative | [JETM](http://jetm.void.fm/), [Apache JMeter](https://jmeter.apache.org/) | Performance (performance testing vs load testing respectively) | No |
+| Structural | Static, white box | [CheckStyle](https://checkstyle.sourceforge.io/) | Constient formatting of the source code | Yes |
+| Structural | Dynamics, white box | [SpotBugs](https://spotbugs.github.io/) | Reocurreing bugs (based on experience of other projects) | No |
+
 ## UI
 
 Global variables should be avoided. Try to pass them as dependency.