Add boilerplate test for oneOf issue; FIXME

tests/schema/core/issues/issue-529.json

+{
+  "description": "...",
+  "tests": [
+    {
+      "description": "should ...",
+      "schema": {
+        "type": "object",
+        "required": [
+          "filters"
+        ],
+        "properties": {
+          "filters": {
+            "type": "array",
+            "items": {
+              "oneOf": [
+                {
+                  "$ref": "#/definitions/FilterAgc"
+                },
+                {
+                  "$ref": "#/definitions/FilterSubspace"
+                }
+              ]
+            }
+          }
+        },
+        "$schema": "http://json-schema.org/draft-06/schema#",
+        "definitions": {
+          "FilterAgc": {
+            "type": "object",
+            "required": [
+              "params"
+            ],
+            "properties": {
+              "params": {
+                "$ref": "#/definitions/FilterAgcParams"
+              },
+              "enabled": {
+                "type": "boolean"
+              }
+            }
+          },
+          "FilterAgcParams": {
+            "type": "object",
+            "required": [
+              "window_length_seconds"
+            ],
+            "properties": {
+              "window_length_seconds": {
+                "type": "number"
+              }
+            }
+          },
+          "FilterSubspace": {
+            "type": "object",
+            "required": [
+              "params"
+            ],
+            "properties": {
+              "params": {
+                "$ref": "#/definitions/FilterSubspaceParams"
+              },
+              "enabled": {
+                "type": "boolean"
+              }
+            }
+          },
+          "FilterSubspaceParams": {
+            "type": "object",
+            "required": [
+              "iterations"
+            ],
+            "properties": {
+              "iterations": {
+                "type": "integer"
+              }
+            }
+          }
+        }
+      },
+      "skip": true,
+      "valid": true
+    }
+  ]
+}