yuicompressor: add test

Closes Homebrew/homebrew#26438.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/yuicompressor.rb

@@ -9,4 +9,16 @@ class Yuicompressor < Formula
     libexec.install "yuicompressor-#{version}.jar"
     bin.write_jar_script libexec/"yuicompressor-#{version}.jar", "yuicompressor"
   end
+
+  test do
+    path = testpath/"test.js"
+    path.write <<-EOS
+      var i = 1;      // foo
+      console.log(i); // bar
+    EOS
+
+    output = `#{bin}/yuicompressor --nomunge --preserve-semi #{path}`.strip
+    assert_equal "var i=1;console.log(i);", output
+    assert_equal 0, $?.exitstatus
+  end
 end