Add doc test

cli/tests/doc/generic_tuple.out

@@ -0,0 +1,2 @@
+function f(): Generic<[string, number]>
+

cli/tests/doc/generic_tuple.ts

@@ -0,0 +1,4 @@
+interface Generic<_T> {}
+export function f(): Generic<[string, number]> {
+  return {};
+}

cli/tests/integration_tests.rs

@@ -45,6 +45,29 @@ fn std_lint() {
   assert!(status.success());
 }
 
+#[test]
+fn doc_tests() {
+    for file in util::root_path().join("cli/tests/doc").as_path().read_dir().unwrap() {
+        let file = file.unwrap();
+        assert!(file.file_type().unwrap().is_file());
+
+        let name = file.file_name();
+        let name = name.to_str().unwrap();
+
+        if name.ends_with(".js") || name.ends_with(".ts") {
+            let doc_path = file.path();
+            let mut out_path = doc_path.clone();
+            out_path.set_extension("out");
+
+            (util::CheckOutputIntegrationTest {
+                args: &format!("doc {}", doc_path.to_str().unwrap()),
+                output: out_path.to_str().unwrap(),
+                ..Default::default()
+            }).run();
+        }
+    }
+}
+
 #[test]
 fn x_deno_warning() {
   let g = util::http_server();