Convert `brew create` test to spec.

Library/Homebrew/test/create_test.rb

-require "testing_env"
-
-class IntegrationCommandTestCreate < IntegrationCommandTestCase
-  def test_create
-    url = "file://#{TEST_FIXTURE_DIR}/tarballs/testball-0.1.tbz"
-    cmd("create", url, "HOMEBREW_EDITOR" => "/bin/cat")
-
-    formula_file = CoreTap.new.formula_dir/"testball.rb"
-    assert formula_file.exist?, "The formula source should have been created"
-    assert_match %Q(sha256 "#{TESTBALL_SHA256}"), formula_file.read
-  end
-end

Library/Homebrew/test/dev-cmd/create_spec.rb

+describe "brew create", :integration_test do
+  let(:url) { "file://#{TEST_FIXTURE_DIR}/tarballs/testball-0.1.tbz" }
+  let(:formula_file) { CoreTap.new.formula_dir/"testball.rb" }
+
+  it "creates a new Formula file for a given URL" do
+    shutup do
+      brew "create", url, "HOMEBREW_EDITOR" => "/bin/cat"
+    end
+
+    expect(formula_file).to exist
+    expect(formula_file.read).to match(%Q(sha256 "#{TESTBALL_SHA256}"))
+  end
+end