astyle: add test

Closes Homebrew/homebrew#35333.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Formula/astyle.rb

@@ -1,5 +1,3 @@
-require "formula"
-
 class Astyle < Formula
   homepage "http://astyle.sourceforge.net/"
   url "https://downloads.sourceforge.net/project/astyle/astyle/astyle%202.05/astyle_2.05_macosx.tar.gz"
@@ -19,4 +17,16 @@ class Astyle < Formula
       bin.install "bin/astyle"
     end
   end
+
+  test do
+    (testpath/"test.c").write("int main(){return 0;}\n")
+    system "#{bin}/astyle", "--style=gnu", "--indent=spaces=4",
+           "--lineend=linux", "#{testpath}/test.c"
+    assert_equal File.read("test.c"), <<-EOS.undent
+      int main()
+      {
+          return 0;
+      }
+    EOS
+  end
 end