Add test for `filter.py`

Inst_eddies/Analysis/tests.json

@@ -113,5 +113,14 @@
 	    "$src_dir/Inst_eddies/Analysis/stat.py",
 	    "$tests_old_dir/Inst_eddies_v6_global/SHPC_anti"
 	]
+    },
+    {
+	"title": "Filter",
+	"command":
+	[
+	    "$src_dir/Inst_eddies/Analysis/filter.py",
+	    "$PWD/Inst_eddies_4_anti",
+	    "plouf"
+	]
     }
 ]