diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 1580091488f20..43561fa4f2fc1 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1264,15 +1264,15 @@ impl Step for Compiletest {
     }
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
-struct DocTest {
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+struct BookTest {
     compiler: Compiler,
-    path: &'static str,
+    path: PathBuf,
     name: &'static str,
     is_ext_doc: bool,
 }
 
-impl Step for DocTest {
+impl Step for BookTest {
     type Output = ();
     const ONLY_HOSTS: bool = true;
 
@@ -1280,12 +1280,59 @@ impl Step for DocTest {
         run.never()
     }
 
-    /// Runs `rustdoc --test` for all documentation in `src/doc`.
+    /// Runs the documentation tests for a book in `src/doc`.
     ///
-    /// This will run all tests in our markdown documentation (e.g., the book)
-    /// located in `src/doc`. The `rustdoc` that's run is the one that sits next to
-    /// `compiler`.
+    /// This uses the `rustdoc` that sits next to `compiler`.
     fn run(self, builder: &Builder<'_>) {
+        // External docs are different from local because:
+        // - Some books need pre-processing by mdbook before being tested.
+        // - They need to save their state to toolstate.
+        // - They are only tested on the "checktools" builders.
+        //
+        // The local docs are tested by default, and we don't want to pay the
+        // cost of building mdbook, so they use `rustdoc --test` directly.
+        // Also, the unstable book is special because SUMMARY.md is generated,
+        // so it is easier to just run `rustdoc` on its files.
+        if self.is_ext_doc {
+            self.run_ext_doc(builder);
+        } else {
+            self.run_local_doc(builder);
+        }
+    }
+}
+
+impl BookTest {
+    /// This runs the equivalent of `mdbook test` (via the rustbook wrapper)
+    /// which in turn runs `rustdoc --test` on each file in the book.
+    fn run_ext_doc(self, builder: &Builder<'_>) {
+        let compiler = self.compiler;
+
+        builder.ensure(compile::Std { compiler, target: compiler.host });
+
+        // mdbook just executes a binary named "rustdoc", so we need to update
+        // PATH so that it points to our rustdoc.
+        let mut rustdoc_path = builder.rustdoc(compiler);
+        rustdoc_path.pop();
+        let old_path = env::var_os("PATH").unwrap_or_default();
+        let new_path = env::join_paths(iter::once(rustdoc_path).chain(env::split_paths(&old_path)))
+            .expect("could not add rustdoc to PATH");
+
+        let mut rustbook_cmd = builder.tool_cmd(Tool::Rustbook);
+        let path = builder.src.join(&self.path);
+        rustbook_cmd.env("PATH", new_path).arg("test").arg(path);
+        builder.add_rust_test_threads(&mut rustbook_cmd);
+        builder.info(&format!("Testing rustbook {}", self.path.display()));
+        let _time = util::timeit(&builder);
+        let toolstate = if try_run(builder, &mut rustbook_cmd) {
+            ToolState::TestPass
+        } else {
+            ToolState::TestFail
+        };
+        builder.save_toolstate(self.name, toolstate);
+    }
+
+    /// This runs `rustdoc --test` on all `.md` files in the path.
+    fn run_local_doc(self, builder: &Builder<'_>) {
         let compiler = self.compiler;
 
         builder.ensure(compile::Std { compiler, target: compiler.host });
@@ -1294,7 +1341,6 @@ impl Step for DocTest {
         // tests for all files that end in `*.md`
         let mut stack = vec![builder.src.join(self.path)];
         let _time = util::timeit(&builder);
-
         let mut files = Vec::new();
         while let Some(p) = stack.pop() {
             if p.is_dir() {
@@ -1306,25 +1352,13 @@ impl Step for DocTest {
                 continue;
             }
 
-            // The nostarch directory in the book is for no starch, and so isn't
-            // guaranteed to builder. We don't care if it doesn't build, so skip it.
-            if p.to_str().map_or(false, |p| p.contains("nostarch")) {
-                continue;
-            }
-
             files.push(p);
         }
 
         files.sort();
 
-        let mut toolstate = ToolState::TestPass;
         for file in files {
-            if !markdown_test(builder, compiler, &file) {
-                toolstate = ToolState::TestFail;
-            }
-        }
-        if self.is_ext_doc {
-            builder.save_toolstate(self.name, toolstate);
+            markdown_test(builder, compiler, &file);
         }
     }
 }
@@ -1353,9 +1387,9 @@ macro_rules! test_book {
                 }
 
                 fn run(self, builder: &Builder<'_>) {
-                    builder.ensure(DocTest {
+                    builder.ensure(BookTest {
                         compiler: self.compiler,
-                        path: $path,
+                        path: PathBuf::from($path),
                         name: $book_name,
                         is_ext_doc: !$default,
                     });
diff --git a/src/doc/book b/src/doc/book
index 87dd684367857..6fb3705e52303 160000
--- a/src/doc/book
+++ b/src/doc/book
@@ -1 +1 @@
-Subproject commit 87dd6843678575f8dda962f239d14ef4be14b352
+Subproject commit 6fb3705e5230311b096d47f7e2c91f9ce24393d0
diff --git a/src/doc/edition-guide b/src/doc/edition-guide
index 1a2390247ad6d..37f9e68484111 160000
--- a/src/doc/edition-guide
+++ b/src/doc/edition-guide
@@ -1 +1 @@
-Subproject commit 1a2390247ad6d08160e0dd74f40a01a9578659c2
+Subproject commit 37f9e6848411188a1062ead1bd8ebe4b8aa16899
diff --git a/src/doc/embedded-book b/src/doc/embedded-book
index 4d78994915af1..b2e1092bf67bd 160000
--- a/src/doc/embedded-book
+++ b/src/doc/embedded-book
@@ -1 +1 @@
-Subproject commit 4d78994915af1bde9a95c04a8c27d8dca066232a
+Subproject commit b2e1092bf67bd4d7686c4553f186edbb7f5f92db
diff --git a/src/doc/reference b/src/doc/reference
index 11e893fc1357b..64239df6d1735 160000
--- a/src/doc/reference
+++ b/src/doc/reference
@@ -1 +1 @@
-Subproject commit 11e893fc1357bc688418ddf1087c2b7aa25d154d
+Subproject commit 64239df6d173562b9deb4f012e4c3e6e960c4754
diff --git a/src/doc/rust-by-example b/src/doc/rust-by-example
index 1c2bd024d13f8..32facd5522ddb 160000
--- a/src/doc/rust-by-example
+++ b/src/doc/rust-by-example
@@ -1 +1 @@
-Subproject commit 1c2bd024d13f8011307e13386cf1fea2180352b5
+Subproject commit 32facd5522ddbbf37baf01e4e4b6562bc55c071a
diff --git a/src/doc/rustdoc/book.toml b/src/doc/rustdoc/book.toml
new file mode 100644
index 0000000000000..ba30c107667ed
--- /dev/null
+++ b/src/doc/rustdoc/book.toml
@@ -0,0 +1,4 @@
+[book]
+authors = ["The Rust Project Developers"]
+src = "src"
+title = "The rustdoc book"
diff --git a/src/tools/rustbook/src/main.rs b/src/tools/rustbook/src/main.rs
index 023f5aa1e284b..ca4bf4ea662c5 100644
--- a/src/tools/rustbook/src/main.rs
+++ b/src/tools/rustbook/src/main.rs
@@ -25,6 +25,11 @@ fn main() {
                 .arg_from_usage(d_message)
                 .arg_from_usage(dir_message),
         )
+        .subcommand(
+            SubCommand::with_name("test")
+                .about("Tests that a book's Rust code samples compile")
+                .arg_from_usage(dir_message),
+        )
         .subcommand(
             SubCommand::with_name("linkcheck")
                 .about("Run linkcheck with mdBook 3")
@@ -36,13 +41,12 @@ fn main() {
     match matches.subcommand() {
         ("build", Some(sub_matches)) => {
             if let Err(e) = build(sub_matches) {
-                eprintln!("Error: {}", e);
-
-                for cause in e.iter().skip(1) {
-                    eprintln!("\tCaused By: {}", cause);
-                }
-
-                ::std::process::exit(101);
+                handle_error(e);
+            }
+        }
+        ("test", Some(sub_matches)) => {
+            if let Err(e) = test(sub_matches) {
+                handle_error(e);
             }
         }
         ("linkcheck", Some(sub_matches)) => {
@@ -146,6 +150,12 @@ pub fn build(args: &ArgMatches<'_>) -> Result3<()> {
     Ok(())
 }
 
+fn test(args: &ArgMatches<'_>) -> Result3<()> {
+    let book_dir = get_book_dir(args);
+    let mut book = MDBook::load(&book_dir)?;
+    book.test(vec![])
+}
+
 fn get_book_dir(args: &ArgMatches<'_>) -> PathBuf {
     if let Some(dir) = args.value_of("dir") {
         // Check if path is relative from current dir, or absolute...
@@ -155,3 +165,13 @@ fn get_book_dir(args: &ArgMatches<'_>) -> PathBuf {
         env::current_dir().unwrap()
     }
 }
+
+fn handle_error(error: mdbook::errors::Error) -> ! {
+    eprintln!("Error: {}", error);
+
+    for cause in error.iter().skip(1) {
+        eprintln!("\tCaused By: {}", cause);
+    }
+
+    ::std::process::exit(101);
+}
diff --git a/src/tools/tidy/src/lib.rs b/src/tools/tidy/src/lib.rs
index c8c61b6fb5015..be1e598d8d4fe 100644
--- a/src/tools/tidy/src/lib.rs
+++ b/src/tools/tidy/src/lib.rs
@@ -58,6 +58,7 @@ fn filter_dirs(path: &Path) -> bool {
         "src/tools/rls",
         "src/tools/rust-installer",
         "src/tools/rustfmt",
+        "src/doc/book",
         // Filter RLS output directories
         "target/rls",
     ];