diff --git a/crates/webidl/Cargo.toml b/crates/webidl/Cargo.toml
index c37b3989a..fb23661c4 100644
--- a/crates/webidl/Cargo.toml
+++ b/crates/webidl/Cargo.toml
@@ -9,6 +9,7 @@ path = "tests/all/lib.rs"
 
 [dev-dependencies]
 wasm-bindgen-backend = { version = "=0.2.11", path = "../backend", features = ["extra-traits"] }
+diff = "0.1.11"
 
 [dependencies]
 failure = "0.1"
diff --git a/crates/webidl/tests/all/event.rs b/crates/webidl/tests/all/event.rs
deleted file mode 100644
index 54facf3d5..000000000
--- a/crates/webidl/tests/all/event.rs
+++ /dev/null
@@ -1,24 +0,0 @@
-use super::backend;
-use proc_macro2;
-use syn;
-
-assert_parse!(
-    event,
-    include_str!("./Event.webidl"),
-    backend::ast::Program {
-        exports: vec![],
-        imports: vec![backend::ast::Import {
-            module: None,
-            version: None,
-            js_namespace: None,
-            kind: backend::ast::ImportKind::Type(backend::ast::ImportType {
-                vis: syn::Visibility::Public(syn::VisPublic {
-                    pub_token: Default::default(),
-                }),
-                name: syn::Ident::new("Event", proc_macro2::Span::call_site()),
-            }),
-        }],
-        enums: vec![],
-        structs: vec![],
-    }
-);
diff --git a/crates/webidl/tests/all/lib.rs b/crates/webidl/tests/all/lib.rs
index bcb50c280..522af500d 100644
--- a/crates/webidl/tests/all/lib.rs
+++ b/crates/webidl/tests/all/lib.rs
@@ -1,21 +1,41 @@
+extern crate diff;
 extern crate proc_macro2;
 extern crate syn;
 extern crate wasm_bindgen_backend as backend;
 extern crate wasm_bindgen_webidl as wb_webidl;
 
-pub fn assert_parse(webidl: &str, expected: backend::ast::Program) {
-    let actual = wb_webidl::parse(webidl).expect("should parse the webidl source OK");
-    assert_eq!(expected, actual);
-}
+#[macro_use]
+mod util;
+use util::*;
 
-macro_rules! assert_parse {
-    ($test_name:ident, $webidl_source:expr, $expected_ast:expr) => {
-        #[test]
-        fn $test_name() {
-            $crate::assert_parse($webidl_source, $expected_ast);
+/// Tests for parsing WebIDL into an expected wasm-bindgen AST.
+mod parse {
+    use super::*;
+
+    assert_parse!(empty, backend::ast::Program::default());
+
+    assert_parse!(
+        Event,
+        backend::ast::Program {
+            exports: vec![],
+            imports: vec![backend::ast::Import {
+                module: None,
+                version: None,
+                js_namespace: None,
+                kind: backend::ast::ImportKind::Type(backend::ast::ImportType {
+                    vis: syn::Visibility::Public(syn::VisPublic {
+                        pub_token: Default::default(),
+                    }),
+                    name: syn::Ident::new("Event", proc_macro2::Span::call_site()),
+                }),
+            }],
+            enums: vec![],
+            structs: vec![],
         }
-    };
+    );
 }
 
-mod event;
-mod simple;
+/// Tests for compiling WebIDL into Rust bindings.
+mod compile {
+    assert_compile!(Event);
+}
diff --git a/crates/webidl/tests/all/simple.rs b/crates/webidl/tests/all/simple.rs
deleted file mode 100644
index dd2118ef6..000000000
--- a/crates/webidl/tests/all/simple.rs
+++ /dev/null
@@ -1,3 +0,0 @@
-use super::backend;
-
-assert_parse!(empty, "", backend::ast::Program::default());
diff --git a/crates/webidl/tests/all/util.rs b/crates/webidl/tests/all/util.rs
new file mode 100644
index 000000000..06f6be1c6
--- /dev/null
+++ b/crates/webidl/tests/all/util.rs
@@ -0,0 +1,171 @@
+use backend;
+use diff;
+use std::io::{self, Write};
+use std::process;
+use std::sync::{Once, ONCE_INIT};
+use wb_webidl;
+
+pub fn assert_parse(webidl: &str, expected: backend::ast::Program) {
+    let actual = wb_webidl::parse(webidl).expect("should parse the webidl source OK");
+    assert_eq!(expected, actual);
+}
+
+macro_rules! assert_parse {
+    ($test_name:ident, $expected_ast:expr) => {
+        #[test]
+        #[allow(non_snake_case)]
+        fn $test_name() {
+            let webidl_source = include_str!(concat!(
+                env!("CARGO_MANIFEST_DIR"),
+                "/tests/fixtures/",
+                stringify!($test_name),
+                ".webidl"
+            ));
+            $crate::assert_parse(webidl_source, $expected_ast);
+        }
+    };
+}
+
+fn rustfmt<S: Into<String>>(source: S) -> (String, String) {
+    let source = source.into();
+
+    static CHECK_RUSTFMT: Once = ONCE_INIT;
+
+    CHECK_RUSTFMT.call_once(|| {
+        let have_working_rustfmt = process::Command::new("rustup")
+            .args(&["run", "nightly", "rustfmt", "--version"])
+            .stdout(process::Stdio::null())
+            .stderr(process::Stdio::null())
+            .status()
+            .ok()
+            .map_or(false, |status| status.success());
+
+        if !have_working_rustfmt {
+            panic!(
+                "
+The latest `rustfmt` is required to run the `wasm-bindgen` test suite. Install
+`rustfmt` with:
+
+    $ rustup component add rustfmt-preview --toolchain nightly
+"
+            );
+        }
+    });
+
+    let mut child = process::Command::new("rustup")
+        .args(&[
+            "run",
+            "nightly",
+            "rustfmt",
+            "--config-path",
+            concat!(env!("CARGO_MANIFEST_DIR"), "/tests/rustfmt.toml"),
+        ])
+        .stdin(process::Stdio::piped())
+        .stdout(process::Stdio::piped())
+        .stderr(process::Stdio::piped())
+        .spawn()
+        .expect("should spawn `rustup run nightly rustfmt`");
+
+    let mut stdin = child.stdin.take().unwrap();
+    let mut stdout = child.stdout.take().unwrap();
+    let mut stderr = child.stderr.take().unwrap();
+
+    // Write to stdin in a new thread, so that we can read from stdout on this
+    // thread. This keeps the child from blocking on writing to its stdout which
+    // might block us from writing to its stdin.
+    let stdin_handle = ::std::thread::spawn(move || stdin.write_all(source.as_bytes()));
+
+    // Read stderr on a new thread for similar reasons.
+    let stderr_handle = ::std::thread::spawn(move || {
+        let mut output = vec![];
+        io::copy(&mut stderr, &mut output).map(|_| String::from_utf8_lossy(&output).to_string())
+    });
+
+    let mut output = vec![];
+    io::copy(&mut stdout, &mut output).expect("Should copy stdout into vec OK");
+
+    // Ignore actual rustfmt status because it is often non-zero for trivial
+    // things.
+    let _ = child.wait().expect("should wait on rustfmt child OK");
+
+    stdin_handle
+        .join()
+        .expect("writer thread should not have panicked")
+        .expect("should have written to child rustfmt's stdin OK");
+
+    let formatted = String::from_utf8(output).expect("rustfmt should only emit valid utf-8");
+
+    let stderr = stderr_handle
+        .join()
+        .expect("stderr reader thread should not have panicked")
+        .expect("should have read child rustfmt's stderr OK");
+
+    (formatted, stderr)
+}
+
+fn strip_wasm_bindgen_generated(source: String) -> String {
+    let lines: Vec<_> = source
+        .lines()
+        .filter(|l| !l.contains("__WASM_BINDGEN_GENERATED"))
+        .collect();
+    lines.join("\n")
+}
+
+pub fn assert_compile(webidl: &str, expected: &str) {
+    let actual = wb_webidl::compile(webidl).expect("should compile the webidl source OK");
+
+    let (actual, actual_stderr) = rustfmt(actual);
+    let (expected, expected_stderr) = rustfmt(expected);
+
+    let actual = strip_wasm_bindgen_generated(actual);
+    let expected = strip_wasm_bindgen_generated(expected);
+
+    if expected == actual {
+        return;
+    }
+
+    eprintln!("rustfmt(expected) stderr:");
+    eprintln!("{}", expected_stderr);
+    eprintln!();
+
+    eprintln!("rustfmt(actual) stderr:");
+    eprintln!("{}", actual_stderr);
+    eprintln!();
+
+    eprintln!(
+        "assert_compile failed: actual compiled output and expected compiled output do not match:"
+    );
+    eprintln!("--- expected");
+    eprintln!("+++ actual");
+    for d in diff::lines(&expected, &actual) {
+        match d {
+            diff::Result::Left(l) => eprintln!("-{}", l),
+            diff::Result::Right(r) => eprintln!("+{}", r),
+            diff::Result::Both(b, _) => eprintln!(" {}", b),
+        }
+    }
+
+    panic!()
+}
+
+macro_rules! assert_compile {
+    ($test_name:ident) => {
+        #[test]
+        #[allow(non_snake_case)]
+        fn $test_name() {
+            let webidl_source = include_str!(concat!(
+                env!("CARGO_MANIFEST_DIR"),
+                "/tests/fixtures/",
+                stringify!($test_name),
+                ".webidl"
+            ));
+            let expected_output = include_str!(concat!(
+                env!("CARGO_MANIFEST_DIR"),
+                "/tests/expected/",
+                stringify!($test_name),
+                ".rs"
+            ));
+            $crate::assert_compile(webidl_source, expected_output);
+        }
+    };
+}
diff --git a/crates/webidl/tests/expected/Event.rs b/crates/webidl/tests/expected/Event.rs
new file mode 100644
index 000000000..747f964ba
--- /dev/null
+++ b/crates/webidl/tests/expected/Event.rs
@@ -0,0 +1,58 @@
+#[allow(bad_style)]
+pub struct Event {
+    obj: ::wasm_bindgen::JsValue,
+}
+impl ::wasm_bindgen::describe::WasmDescribe for Event {
+    fn describe() {
+        ::wasm_bindgen::JsValue::describe();
+    }
+}
+impl ::wasm_bindgen::convert::IntoWasmAbi for Event {
+    type Abi = <::wasm_bindgen::JsValue as ::wasm_bindgen::convert::IntoWasmAbi>::Abi;
+    fn into_abi(self, extra: &mut ::wasm_bindgen::convert::Stack) -> Self::Abi {
+        self.obj.into_abi(extra)
+    }
+}
+impl ::wasm_bindgen::convert::FromWasmAbi for Event {
+    type Abi = <::wasm_bindgen::JsValue as ::wasm_bindgen::convert::FromWasmAbi>::Abi;
+    unsafe fn from_abi(js: Self::Abi, extra: &mut ::wasm_bindgen::convert::Stack) -> Self {
+        Event {
+            obj: ::wasm_bindgen::JsValue::from_abi(js, extra),
+        }
+    }
+}
+impl<'a> ::wasm_bindgen::convert::IntoWasmAbi for &'a Event {
+    type Abi = <&'a ::wasm_bindgen::JsValue as ::wasm_bindgen::convert::IntoWasmAbi>::Abi;
+    fn into_abi(self, extra: &mut ::wasm_bindgen::convert::Stack) -> Self::Abi {
+        (&self.obj).into_abi(extra)
+    }
+}
+impl ::wasm_bindgen::convert::RefFromWasmAbi for Event {
+    type Abi = <::wasm_bindgen::JsValue as ::wasm_bindgen::convert::RefFromWasmAbi>::Abi;
+    type Anchor = ::wasm_bindgen::__rt::core::mem::ManuallyDrop<Event>;
+    unsafe fn ref_from_abi(
+        js: Self::Abi,
+        extra: &mut ::wasm_bindgen::convert::Stack,
+    ) -> Self::Anchor {
+        let tmp =
+            <::wasm_bindgen::JsValue as ::wasm_bindgen::convert::RefFromWasmAbi>::ref_from_abi(
+                js, extra,
+            );
+        ::wasm_bindgen::__rt::core::mem::ManuallyDrop::new(Event {
+            obj: ::wasm_bindgen::__rt::core::mem::ManuallyDrop::into_inner(tmp),
+        })
+    }
+}
+impl From<::wasm_bindgen::JsValue> for Event {
+    fn from(obj: ::wasm_bindgen::JsValue) -> Event {
+        Event { obj }
+    }
+}
+impl From<Event> for ::wasm_bindgen::JsValue {
+    fn from(obj: Event) -> ::wasm_bindgen::JsValue {
+        obj.obj
+    }
+}
+#[allow(non_upper_case_globals)]
+#[wasm_custom_section = "__wasm_bindgen_unstable"]
+const __WASM_BINDGEN_GENERATED_wasm_bindgen_webidl_0_1_0_0 : [ u8 ; 180usize ] = * b"\xB0\0\0\0{\"exports\":[],\"enums\":[],\"imports\":[{\"module\":null,\"version\":null,\"js_namespace\":null,\"kind\":{\"kind\":\"type\"}}],\"structs\":[],\"version\":\"0.2.11 (3879f6f42)\",\"schema_version\":\"4\"}" ;
diff --git a/crates/webidl/tests/all/Event.webidl b/crates/webidl/tests/fixtures/Event.webidl
similarity index 100%
rename from crates/webidl/tests/all/Event.webidl
rename to crates/webidl/tests/fixtures/Event.webidl
diff --git a/crates/webidl/tests/fixtures/empty.webidl b/crates/webidl/tests/fixtures/empty.webidl
new file mode 100644
index 000000000..e69de29bb
diff --git a/crates/webidl/tests/rustfmt.toml b/crates/webidl/tests/rustfmt.toml
new file mode 100644
index 000000000..e69de29bb