diff --git a/test/model/extensions/classes/defaults.yml b/test/model/extensions/classes/defaults.yml
new file mode 100644
index 0000000..5d17c2b
--- /dev/null
+++ b/test/model/extensions/classes/defaults.yml
@@ -0,0 +1,4 @@
+
+parameters:
+  config:
+    defaults: True
diff --git a/test/model/extensions/classes/relative/init.yml b/test/model/extensions/classes/relative/init.yml
new file mode 100644
index 0000000..117e4fa
--- /dev/null
+++ b/test/model/extensions/classes/relative/init.yml
@@ -0,0 +1,3 @@
+
+classes:
+  - .nested
diff --git a/test/model/extensions/classes/relative/nested/common.yml b/test/model/extensions/classes/relative/nested/common.yml
new file mode 100644
index 0000000..28cc0b2
--- /dev/null
+++ b/test/model/extensions/classes/relative/nested/common.yml
@@ -0,0 +1,5 @@
+
+parameters:
+  nested:
+    deep:
+      common: to be overriden
diff --git a/test/model/extensions/classes/relative/nested/deep/common.yml b/test/model/extensions/classes/relative/nested/deep/common.yml
new file mode 100644
index 0000000..b77a24c
--- /dev/null
+++ b/test/model/extensions/classes/relative/nested/deep/common.yml
@@ -0,0 +1,5 @@
+
+parameters:
+  nested:
+    deep:
+      common: False
diff --git a/test/model/extensions/classes/relative/nested/deep/init.yml b/test/model/extensions/classes/relative/nested/deep/init.yml
new file mode 100644
index 0000000..cd12d10
--- /dev/null
+++ b/test/model/extensions/classes/relative/nested/deep/init.yml
@@ -0,0 +1,9 @@
+
+classes:
+  - .common
+
+parameters:
+  nested:
+    deep:
+      init: True
+      common: True
diff --git a/test/model/extensions/classes/relative/nested/dive/session.yml b/test/model/extensions/classes/relative/nested/dive/session.yml
new file mode 100644
index 0000000..9abd1ee
--- /dev/null
+++ b/test/model/extensions/classes/relative/nested/dive/session.yml
@@ -0,0 +1,5 @@
+
+parameters:
+  nested:
+    deep:
+      session: True
diff --git a/test/model/extensions/classes/relative/nested/init.yml b/test/model/extensions/classes/relative/nested/init.yml
new file mode 100644
index 0000000..9f02383
--- /dev/null
+++ b/test/model/extensions/classes/relative/nested/init.yml
@@ -0,0 +1,10 @@
+
+classes:
+  - .common
+  - .deep
+  - .dive.session
+
+parameters:
+  nested:
+    deep:
+      init: True
diff --git a/test/model/extensions/classes/second.yml b/test/model/extensions/classes/second.yml
index a9babd3..929d746 100644
--- a/test/model/extensions/classes/second.yml
+++ b/test/model/extensions/classes/second.yml
@@ -1,5 +1,6 @@
 classes:
 - first
+- relative
 
 parameters:
   will:
diff --git a/test/model/extensions/classes/third.yml b/test/model/extensions/classes/third.yml
index 20a937c..a5157cf 100644
--- a/test/model/extensions/classes/third.yml
+++ b/test/model/extensions/classes/third.yml
@@ -1,6 +1,7 @@
 classes:
 - missing.class
 - second
+- .defaults
 
 parameters:
   _param: