Add "Gradle properties" section outlining project properties

README.md

@@ -16,6 +16,7 @@ The StarOpenSource Engine is under heavy development and is extremely unstable.
   - [Code style](#code-style)
   - [Pull request guidelines](#pull-request-guidelines)
   - [Making your first contribution](#making-your-first-contribution)
+  - [Gradle properties](#gradle-properties)
 
 ## About
 ### ... the engine
@@ -65,3 +66,24 @@ Before creating a pull request, make sure you've:
 - is compatible with other applications. If not, tell us in your pull request description.
 ### Making your first contribution
 TODO
+### Gradle properties
+Gradle's behaviour can be changed by changing gradle project properties.
+To change them, simply append `-P<property>` or `-P<property>=<value>`, like this: `./gradlew -Pjobs=4 test`.
+#### Parallelism
+Use the `jobs` property to control how many jobs will get executed simultaneously.
+On Linux, specify `-Pjobs=$(nproc)`. Defaults to `8`.
+#### JVM Home
+You can use the `graalHome` property to specify the `$JAVA_HOME` of your local GraalVM installation.
+Only used in the `nativeImage` task. Useful if you aren't using GraalVM as your primary JDK.
+#### Testing
+You can use the following properties to modify the behaviour of the `test`-task:
+- `test.control.mode` (default *empty*)
+  - `force-enable`: Disables all test classes except the ones specified
+  - `force-disable`: Enables all test classes except the ones specified
+  - *everything else*: Enables all test classes
+- `test.control.classes` (default *empty*): A comma-separated, case-sensitive list of test classes
+  which (depending on `test.control.mode`'s value) enable or disable the specified classes.
+  Example: `-Ptest.control.mode=MiscellaneousTest,DependencyResolverTest,EngineConfigurationTest`
+- `test.control.warning` (default `false`): If `true`, will emit a warning before a restricted test method exits
+- `test.loggerLevel` (default `silent_warning`): Will set `UnitLogger`'s logger level.
+  Works like `-Dsosengine.base.loggerLevel`. See `UnitLogger#loggerLevel` for more information