Add tests for probe/cri/registry

Unhappy path tests try to cover three scenarios:

- When the endpoint URL scheme is not explicitly supported e.g. HTTP
- When the endpoint URL scheme is TCP which is also not supported
- When the fail to parse the given URL (to extract the scheme)

The happy path covers two scenarios:

- When we specify the supported scheme in the URL which is an unix
socket e.g. unix///var/run/dockershim.sock
- When we pass a socket address but fail to specify the scheme but our registry attempts
to use the fallback protocol e.g. var/run/dockershim.sock

probe/cri/registry_test.go

@@ -7,15 +7,36 @@ import (
 	"github.com/weaveworks/scope/probe/cri"
 )
 
-func TestParseHttpEndpointUrl(t *testing.T) {
-	_, err := cri.NewCRIClient("http://xyz.com")
-
-	assert.Equal(t, "protocol \"http\" not supported", err.Error())
+var nonUnixSocketsTest = []struct {
+	endpoint     string
+	errorMessage string
+}{
+	{"http://xyz.com", "protocol \"http\" not supported"},
+	{"tcp://var/unix.sock", "endpoint was not unix socket tcp"},
+	{"http://[fe80::%31]/", "parse http://[fe80::%31]/: invalid URL escape \"%31\""},
 }
 
-func TestParseTcpEndpointUrl(t *testing.T) {
-	client, err := cri.NewCRIClient("127.0.0.1")
+func TestParseNonUnixEndpointUrl(t *testing.T) {
+	for _, tt := range nonUnixSocketsTest {
+		_, err := cri.NewCRIClient(tt.endpoint)
+
+		assert.Equal(t, tt.errorMessage, err.Error())
+	}
+}
+
+var unixSocketsTest = []string{
+	"127.0.0.1", // tests the fallback endpoint
+	"unix://127.0.0.1",
+	"unix///var/run/dockershim.sock",
+	"var/run/dockershim.sock",
+}
+
+func TestParseUnixEndpointUrl(t *testing.T) {
+	for _, tt := range unixSocketsTest {
+		client, err := cri.NewCRIClient(tt)
+
+		assert.Equal(t, nil, err)
+		assert.NotEqual(t, nil, client)
+	}
 
-	assert.Equal(t, nil, err)
-	assert.NotEqual(t, nil, client)
 }