If we write specification where we need to use files and directories we can use the @TempDir annotation on a File or Path instance variable. By using this annotation we make sure the file is created in the directory defined by the Java system property java.io.tmpdir. We could overwrite the temporary root directory using Spock configuration if we want, but the default should be okay for most situations. The @TempDir annotation can actually be used on any class that has a constructor with a File or Path argument. Since Spock 2.2 we can use the FileSystemFixture class provided by Spock. With this class we have a nice DSL to create directory structures and files in a simple matter. We can use the Groovy extensions to File and Path to also immediately create contents for the files. If we want to use the extensions to Path we must make sure we include org.apache.groovy:groovy-nio as dependency to our test runtime classpath. The FileSystemFixture class also has the method copyFromClasspath that we can use to copy files and their content directory into our newly created directory structure.

In order to add default JVM options to our Maven mvn command we can define an environment variable MAVEN_OPTS. But we can also create a file jvm.config in the directory .mvn in our project root directory. On each line we define a Java option we want to apply. We can specify JVM options, but also Java system properties we want to apply each time we run the mvn command. This directory and file can be added to our source control so that all users that have access to the repository will use the same JVM options.

A version catalog in Gradle is a central place in our project where we can define dependency references with their version or version rules. We can define a version catalog using an API in our build file, but we can also create an external file where we define our dependencies and version. In our dependencies section we can refer to the names in the version catalog using a type-safe accessor (if we use Kotlin for writing our build script) with code completion in a supported IDE (IntelliJ IDEA). If we want to share a version catalog between projects we can publish a version catalog to a Maven repository with a groupId, artifactId and version.

Since Spock 2.1 we have 2 new operators we can use for assertions to check collections: =~ and ==~. We can use these operators with implementations of the Iterable interface when we want to check that a given collection has the same elements as an expected collection and we don’t care about the order of the elements. Without the new operators we would have to cast our collections to a Set first and than use the == operator.

If you are familiar with the layers architectural pattern, it is only a small step to the even nicer hexagonal pattern. Here is an example of how you can do it.

A Software Bill of Materials (SBOM) is a broad inventory of all components, libraries, and other third-party assets used in a software application. It’s a detailed list of all the components that go into the software, much like a recipe lists the ingredients needed to prepare a dish.