Migrate failing_alternate_backend to BookTest

tests/alternative_backends.rs

@@ -6,13 +6,6 @@ use std::fs;
 use std::path::Path;
 use tempfile::{Builder as TempFileBuilder, TempDir};
 
-#[test]
-fn failing_alternate_backend() {
-    let (md, _temp) = dummy_book_with_backend("failing", fail_cmd(), false);
-
-    md.build().unwrap_err();
-}
-
 #[test]
 fn missing_backends_are_fatal() {
     let (md, _temp) = dummy_book_with_backend("missing", "trduyvbhijnorgevfuhn", false);
@@ -128,14 +121,6 @@ fn dummy_book_with_backend(
     (md, temp)
 }
 
-fn fail_cmd() -> &'static str {
-    if cfg!(windows) {
-        r#"cmd.exe /c "exit 1""#
-    } else {
-        "false"
-    }
-}
-
 fn rust_exe(temp: &Path, name: &str, src: &str) {
     let rs = temp.join(name).with_extension("rs");
     fs::write(&rs, src).unwrap();

tests/testsuite/renderer.rs

@@ -36,3 +36,39 @@ fn runs_renderers() {
     let inner = spy.lock().unwrap();
     assert_eq!(inner.run_count, 1);
 }
+
+// Test renderer with a failing command fails.
+#[test]
+fn failing_command() {
+    BookTest::init(|_| {})
+        .rust_program(
+            "failing",
+            r#"
+            fn main() {
+                // Read from stdin to avoid random pipe failures on Linux.
+                use std::io::Read;
+                let mut s = String::new();
+                std::io::stdin().read_to_string(&mut s).unwrap();
+                std::process::exit(1);
+            }
+            "#,
+        )
+        .change_file(
+            "book.toml",
+            "[output.failing]\n\
+             command = './failing'\n",
+        )
+        .run("build", |cmd| {
+            cmd.expect_failure()
+                .expect_stdout(str![[""]])
+                .expect_stderr(str![[r#"
+[TIMESTAMP] [INFO] (mdbook::book): Book building has started
+[TIMESTAMP] [INFO] (mdbook::book): Running the failing backend
+[TIMESTAMP] [INFO] (mdbook::renderer): Invoking the "failing" renderer
+[TIMESTAMP] [ERROR] (mdbook::renderer): Renderer exited with non-zero return code.
+[TIMESTAMP] [ERROR] (mdbook::utils): Error: Rendering failed
+[TIMESTAMP] [ERROR] (mdbook::utils): [TAB]Caused By: The "failing" renderer failed
+
+"#]]);
+        });
+}