fix some tests, split up and refactor

some wonky regression introduced by docker dependencies when running on darwin. see https://github.com/ory/dockertest/issues/212 for more info.
will have a look at this next

pkg/registry/helpers/helpers_test.go

@@ -0,0 +1,33 @@
+package helpers
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	log "github.com/sirupsen/logrus"
+	"testing"
+)
+
+func TestDigest(t *testing.T) {
+	log.SetLevel(log.DebugLevel)
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Digest Suite")
+}
+
+var _ = Describe("the helpers", func() {
+
+	When("converting an url to a hostname", func() {
+		It("should return docker.io given docker.io/containrrr/watchtower:latest", func() {
+			host, port, err := ConvertToHostname("docker.io/containrrr/watchtower:latest")
+			Expect(err).NotTo(HaveOccurred())
+			Expect(host).To(Equal("docker.io"))
+			Expect(port).To(BeEmpty())
+		})
+	})
+	When("normalizing the registry information", func() {
+		It("should return index.docker.io given docker.io", func() {
+			out, err := NormalizeRegistry("docker.io/containrrr/watchtower:latest")
+			Expect(err).NotTo(HaveOccurred())
+			Expect(out).To(Equal("index.docker.io"))
+		})
+	})
+})