libvorbis: add test

Formula/libvorbis.rb

@@ -23,10 +23,36 @@ class Libvorbis < Formula
   depends_on "pkg-config" => :build
   depends_on "libogg"
 
+  resource("oggfile") do
+    url "https://upload.wikimedia.org/wikipedia/commons/c/c8/Example.ogg"
+    sha256 "379071af4fa77bc7dacf892ad81d3f92040a628367d34a451a2cdcc997ef27b0"
+  end
+
   def install
     system "./autogen.sh" if build.head?
     system "./configure", "--disable-dependency-tracking",
                           "--prefix=#{prefix}"
     system "make", "install"
   end
+
+  test do
+    (testpath/"test.c").write <<-EOS.undent
+      #include <stdio.h>
+      #include <assert.h>
+      #include "vorbis/vorbisfile.h"
+      int main (void) {
+        OggVorbis_File vf;
+        assert (ov_open_callbacks (stdin, &vf, NULL, 0, OV_CALLBACKS_NOCLOSE) >= 0);
+        vorbis_info *vi = ov_info (&vf, -1);
+        printf("Bitstream is %d channel, %ldHz\\n", vi->channels, vi->rate);
+        printf("Encoded by: %s\\n", ov_comment(&vf,-1)->vendor);
+        return 0;
+      }
+    EOS
+    testpath.install resource("oggfile")
+    system ENV.cc, "test.c", "-I#{include}", "-L#{lib}", "-lvorbisfile",
+                   "-o", "test"
+    assert_match "2 channel, 44100Hz\nEncoded by: Xiph.Org libVorbis",
+                 shell_output("./test < Example.ogg")
+  end
 end