Migrate theme_dir_overrides_work_correctly to BookTest

tests/rendered_output.rs

@@ -270,24 +270,6 @@ fn example_book_can_build() {
     md.build().unwrap();
 }
 
-#[test]
-fn theme_dir_overrides_work_correctly() {
-    let book_dir = dummy_book::new_copy_of_example_book().unwrap();
-    let book_dir = book_dir.path();
-    let theme_dir = book_dir.join("theme");
-
-    let mut index = mdbook::theme::INDEX.to_vec();
-    index.extend_from_slice(b"\n<!-- This is a modified index.hbs! -->");
-
-    write_file(&theme_dir, "index.hbs", &index).unwrap();
-
-    let md = MDBook::load(book_dir).unwrap();
-    md.build().unwrap();
-
-    let built_index = book_dir.join("book").join("index.html");
-    dummy_book::assert_contains_strings(built_index, &["This is a modified index.hbs!"]);
-}
-
 /// Checks formatting of summary names with inline elements.
 #[test]
 fn summary_with_markdown_formatting() {

tests/testsuite/theme.rs

@@ -30,3 +30,15 @@ fn empty_theme() {
 "#]]);
     });
 }
+
+// Checks overriding index.hbs.
+#[test]
+fn override_index() {
+    BookTest::from_dir("theme/override_index").check_file(
+        "book/index.html",
+        str![[r#"
+This is a modified index.hbs!
+
+"#]],
+    );
+}

tests/testsuite/theme/override_index/src/SUMMARY.md

@@ -0,0 +1 @@
+- [Intro](index.md)

tests/testsuite/theme/override_index/theme/index.hbs

@@ -0,0 +1 @@
+This is a modified index.hbs!