diff --git a/bin/tests/scenarios/functional-interface/base.java b/bin/tests/scenarios/functional-interface/base.java
new file mode 100644
index 0000000..c0a379f
--- /dev/null
+++ b/bin/tests/scenarios/functional-interface/base.java
@@ -0,0 +1,25 @@
+public class CostModelMatcher<T extends Artifact<T>> implements MatcherInterface<T> {
+    private static final Logger LOG = Logger.getLogger(CostModelMatcher.class.getCanonicalName());
+
+    /**
+     * A function weighing a matching that incurred a cost.
+     *
+     * @param <T> the type of the artifacts
+     */
+    @FunctionalInterface
+    public interface SimpleWeightFunction<T extends Artifact<T>> {
+
+        float weigh(CMMatching<T> matching);
+    }
+
+    /**
+     * A function weighing a matching that incurred a specific cost.
+     *
+     * @param <T> the type of the artifacts
+     */
+    @FunctionalInterface
+    public interface WeightFunction<T extends Artifact<T>> {
+
+        float weigh(CMMatching<T> matching, float quantity);
+    }
+}
\ No newline at end of file
diff --git a/bin/tests/scenarios/functional-interface/left.java b/bin/tests/scenarios/functional-interface/left.java
new file mode 100644
index 0000000..d40c65c
--- /dev/null
+++ b/bin/tests/scenarios/functional-interface/left.java
@@ -0,0 +1,26 @@
+public class CostModelMatcher<T extends Artifact<T>> implements MatcherInterface<T> {
+    private static final Logger LOG = Logger.getLogger(CostModelMatcher.class.getCanonicalName());
+
+    /**
+     * A function weighing a matching that incurred a cost.
+     *
+     * @param <T> the type of the artifacts
+     */
+    @FunctionalInterface
+    public interface SimpleWeightFunction<T extends Artifact<T>> {
+
+        float weigh(CMMatching<T> matching);
+        float weight(CMMatching<T> matching);
+    }
+
+    /**
+     * A function weighing a matching that incurred a specific cost.
+     *
+     * @param <T> the type of the artifacts
+     */
+    @FunctionalInterface
+    public interface WeightFunction<T extends Artifact<T>> {
+
+        float weigh(CMMatching<T> matching, float quantity);
+    }
+}
\ No newline at end of file
diff --git a/bin/tests/scenarios/functional-interface/merge.java b/bin/tests/scenarios/functional-interface/merge.java
new file mode 100644
index 0000000..947b160
--- /dev/null
+++ b/bin/tests/scenarios/functional-interface/merge.java
@@ -0,0 +1 @@
+   public class CostModelMatcher  <  T  extends  Artifact  < T > >  implements   MatcherInterface  < T >  {   private static final Logger  LOG =  Logger . getLogger  (   CostModelMatcher . class . getCanonicalName  ( ) ) ;    @ FunctionalInterface public interface SimpleWeightFunction  <  T  extends  Artifact  < T > >  {   float weigh  (   CMMatching  < T > matching ) ;   float weight  (   CMMatching  < T > matching ) ; }    @ FunctionalInterface public interface WeightFunction  <  T  extends  Artifact  < T > >  {   float weigh  (   CMMatching  < T > matching ,   float quantity ) ;   float weight  (   CMMatching  < T > matching ,   float quantity ) ; } }
\ No newline at end of file
diff --git a/bin/tests/scenarios/functional-interface/right.java b/bin/tests/scenarios/functional-interface/right.java
new file mode 100644
index 0000000..43e8153
--- /dev/null
+++ b/bin/tests/scenarios/functional-interface/right.java
@@ -0,0 +1,26 @@
+public class CostModelMatcher<T extends Artifact<T>> implements MatcherInterface<T> {
+    private static final Logger LOG = Logger.getLogger(CostModelMatcher.class.getCanonicalName());
+
+    /**
+     * A function weighing a matching that incurred a cost.
+     *
+     * @param <T> the type of the artifacts
+     */
+    @FunctionalInterface
+    public interface SimpleWeightFunction<T extends Artifact<T>> {
+
+        float weigh(CMMatching<T> matching);
+    }
+
+    /**
+     * A function weighing a matching that incurred a specific cost.
+     *
+     * @param <T> the type of the artifacts
+     */
+    @FunctionalInterface
+    public interface WeightFunction<T extends Artifact<T>> {
+
+        float weigh(CMMatching<T> matching, float quantity);
+        float weight(CMMatching<T> matching, float quantity);
+    }
+}
\ No newline at end of file
diff --git a/matching_handlers/src/java/mod.rs b/matching_handlers/src/java/mod.rs
index 27bfe5b..4fd7f06 100644
--- a/matching_handlers/src/java/mod.rs
+++ b/matching_handlers/src/java/mod.rs
@@ -39,5 +39,9 @@ pub fn get_default_java_matching_handlers<'a>() -> MatchingHandlers<'a> {
         "enum_declaration",
         compute_matching_score_for_class_like_declaration,
     );
+    matching_handlers.register(
+        "interface_declaration",
+        compute_matching_score_for_class_like_declaration,
+    );
     matching_handlers
 }