Add the ability to pass options to browser-ui-test

This adds the ability to pass options to browser-ui-test, which can help
with debugging or doing things like snapshot work. It's maybe not the
cleanest since it doesn't support space-separated args, but should be
good enough.

Author: ehuss

tests/gui/runner.rs

@@ -83,24 +83,22 @@ fn main() {
 
     let book_dir = format!("file://{}", current_dir.join("test_book/book/").display());
 
-    let mut no_headless = false;
+    let mut command = Command::new("npx");
+    command
+        .arg("browser-ui-test")
+        .args(["--variable", "DOC_PATH", book_dir.as_str()]);
+
     let mut filters = Vec::new();
     for arg in std::env::args().skip(1) {
         if arg == "--disable-headless-test" {
-            no_headless = true;
+            command.arg("--no-headless");
+        } else if arg.starts_with("--") {
+            command.arg(arg);
         } else {
             filters.push(arg);
         }
     }
 
-    let mut command = Command::new("npx");
-    command
-        .arg("browser-ui-test")
-        .args(["--variable", "DOC_PATH", book_dir.as_str()]);
-    if no_headless {
-        command.arg("--no-headless");
-    }
-
     let test_dir = "tests/gui";
     if filters.is_empty() {
         command.args(["--test-folder", test_dir]);