Compare cargo-expand output against expected in CI

.github/workflows/ci.yml

@@ -6,13 +6,22 @@ on:
   schedule: [cron: "40 1 * * *"]
 
 jobs:
-  test:
+  nightly:
+    name: Rust nightly
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dtolnay/rust-toolchain@nightly
+      - run: cargo run -- expand --manifest-path tests/Cargo.toml > expand.rs
+      - run: diff tests/lib.expand.rs expand.rs
+
+  build:
     name: Rust ${{matrix.rust}}
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:
-        rust: [nightly, beta, stable, 1.44.0]
+        rust: [beta, stable, 1.44.0]
     steps:
       - uses: actions/checkout@v2
       - uses: dtolnay/rust-toolchain@master

.gitignore

@@ -1 +1,2 @@
+expand.rs
 target

Cargo.lock

@@ -173,6 +173,10 @@ dependencies = [
  "toolchain_find",
 ]
 
+[[package]]
+name = "cargo-expand-test"
+version = "0.0.0"
+
 [[package]]
 name = "cc"
 version = "1.0.66"

Cargo.toml

@@ -10,6 +10,7 @@ keywords = ["cargo", "subcommand", "expanded"]
 categories = ["development-tools::cargo-plugins", "development-tools::debugging"]
 edition = "2018"
 readme = "README.md"
+autotests = false
 
 [dependencies]
 atty = "0.2"
@@ -35,3 +36,6 @@ features = ["full", "parsing", "printing", "visit-mut"]
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]
+
+[workspace]
+members = ["tests"]

tests/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "cargo-expand-test"
+version = "0.0.0"
+edition = "2018"
+publish = false
+
+[lib]
+path = "lib.rs"

tests/lib.expand.rs

@@ -0,0 +1,6 @@
+#![feature(prelude_import)]
+#[prelude_import]
+use std::prelude::v1::*;
+#[macro_use]
+extern crate std;
+pub fn test() {}

tests/lib.rs

@@ -0,0 +1 @@
+pub fn test() {}