AST: add printAST test case

ql/test/library-tests/ast/Ast.ql

@@ -0,0 +1,24 @@
+/**
+ * @kind graph
+ */
+
+import codeql_ruby.printAst
+
+class OrderedAstNode extends PrintAstNode {
+  override string getProperty(string key) {
+    result = super.getProperty(key)
+    or
+    key = "semmle.order" and
+    result =
+      any(int i |
+        this =
+          rank[i](AstNode p |
+            |
+            p
+            order by
+              p.getLocation().getFile().getBaseName(), p.getLocation().getFile().getAbsolutePath(),
+              p.getLocation().getStartLine()
+          )
+      ).toString()
+  }
+}