Migrate missing theme to BookTest

tests/rendered_output.rs

@@ -357,22 +357,6 @@ fn failure_on_missing_theme_directory() {
     let md = MDBook::load(temp.path()).unwrap();
     let got = md.build();
     assert!(got.is_ok());
-
-    // 3. Pointing to a non-existent directory should fail
-    let temp = DummyBook::new().build().unwrap();
-    let book_toml = r#"
-        [book]
-        title = "implicit"
-        src = "src"
-
-        [output.html]
-        theme = "./non-existent-directory"
-        "#;
-
-    write_file(temp.path(), "book.toml", book_toml.as_bytes()).unwrap();
-    let md = MDBook::load(temp.path()).unwrap();
-    let got = md.build();
-    assert!(got.is_err());
 }
 
 #[test]

tests/testsuite/main.rs

@@ -18,6 +18,7 @@ mod rendering;
 #[cfg(feature = "search")]
 mod search;
 mod test;
+mod theme;
 
 mod prelude {
     pub use crate::book_test::BookTest;

tests/testsuite/theme.rs

@@ -0,0 +1,19 @@
+//! Tests for theme handling.
+
+use crate::prelude::*;
+
+// Checks what happens if the theme directory is missing.
+#[test]
+fn missing_theme() {
+    BookTest::from_dir("theme/missing_theme")
+    .run("build", |cmd| {
+cmd.expect_failure()
+        .expect_stderr(str![[r#"
+[TIMESTAMP] [INFO] (mdbook::book): Book building has started
+[TIMESTAMP] [INFO] (mdbook::book): Running the html backend
+[TIMESTAMP] [ERROR] (mdbook::utils): Error: Rendering failed
+[TIMESTAMP] [ERROR] (mdbook::utils): [TAB]Caused By: theme dir [ROOT]/./non-existent-directory does not exist
+
+"#]]);
+    });
+}

tests/testsuite/theme/missing_theme/book.toml

@@ -0,0 +1,5 @@
+[book]
+title = "missing_theme"
+
+[output.html]
+theme = "./non-existent-directory"

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

@@ -0,0 +1,3 @@
+# Summary
+
+- [Chapter 1](./chapter_1.md)

tests/testsuite/theme/missing_theme/src/chapter_1.md

@@ -0,0 +1 @@
+# Chapter 1