Ruby: add tree-sitter test case

ruby/ql/test/library-tests/ast/TreeSitter.ql

@@ -0,0 +1,31 @@
+/**
+ * @kind graph
+ */
+
+import codeql.ruby.ast.internal.TreeSitter::Ruby
+
+/**
+ * Holds if `node` belongs to the output tree, and its property `key` has the
+ * given `value`.
+ */
+query predicate nodes(AstNode node, string key, string value) {
+  key = "semmle.label" and
+  value = "[" + node.getPrimaryQlClasses() + "] " + node.toString()
+}
+
+/**
+ * Holds if `target` is a child of `source` in the AST, and property `key` of
+ * the edge has the given `value`.
+ */
+query predicate edges(AstNode source, AstNode target, string key, string value) {
+  source = target.getParent() and
+  key = ["semmle.label", "semmle.order"] and
+  value = target.getParentIndex().toString()
+}
+
+/**
+ * Holds if property `key` of the graph has the given `value`.
+ */
+query predicate graphProperties(string key, string value) {
+  key = "semmle.graphKind" and value = "tree"
+}