Move testfixtures to own artifact

sop-java-testfixtures/src/main/java/sop/testsuite/SOPInstanceFactory.java

@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: 2023 Paul Schaub <vanitasvitae@fsfe.org>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package sop.testsuite;
+
+import sop.SOP;
+
+import java.util.Map;
+
+/**
+ * Factory class to instantiate SOP implementations for testing.
+ * Overwrite this class and the {@link #provideSOPInstances()} method to return the SOP instances you want
+ * to test.
+ * Then, add the following line to your <pre>build.gradle</pre> files <pre>dependencies</pre> section:
+ * <pre>{@code
+ *     testImplementation(testFixtures("org.pgpainless:sop-java:<version>"))
+ * }</pre>
+ * To inject the factory class into the test suite, add the following line to your modules <pre>test</pre> task:
+ * <pre>{@code
+ *     environment("test.implementation", "org.example.YourTestSubjectFactory")
+ * }</pre>
+ * Next, in your <pre>test</pre> sources, extend all test classes from the <pre>testFixtures</pre>
+ * <pre>sop.operation</pre> package.
+ * Take a look at the <pre>external-sop</pre> module for an example.
+ */
+public abstract class SOPInstanceFactory {
+
+    public abstract Map<String, SOP> provideSOPInstances();
+}