Add test for brew style.

Library/Homebrew/test/cmd/style_spec.rb

@@ -0,0 +1,34 @@
+require "cmd/style"
+
+describe "brew style" do
+  around(:each) do |example|
+    begin
+      FileUtils.ln_s HOMEBREW_LIBRARY_PATH, HOMEBREW_LIBRARY/"Homebrew"
+      FileUtils.ln_s HOMEBREW_LIBRARY_PATH.parent/".rubocop.yml", HOMEBREW_LIBRARY/".rubocop.yml"
+
+      example.run
+    ensure
+      FileUtils.rm_f HOMEBREW_LIBRARY/"Homebrew"
+      FileUtils.rm_f HOMEBREW_LIBRARY/".rubocop.yml"
+    end
+  end
+
+  describe "Homebrew::check_style_json" do
+    let(:dir) { mktmpdir }
+
+    it "returns RubocopResults when RuboCop reports offenses" do
+      formula = dir/"my-formula.rb"
+
+      formula.write <<-'EOS'.undent
+        class MyFormula < Formula
+
+        end
+      EOS
+
+      rubocop_result = Homebrew.check_style_json([formula])
+
+      expect(rubocop_result.file_offenses(formula.realpath.to_s).map(&:message))
+        .to include("Extra empty line detected at class body beginning.")
+    end
+  end
+end