diff --git a/go/mysql/instance_key_test.go b/go/mysql/instance_key_test.go
new file mode 100644
index 0000000..73e22f3
--- /dev/null
+++ b/go/mysql/instance_key_test.go
@@ -0,0 +1,58 @@
+/*
+   Copyright 2016 GitHub Inc.
+	 See https://github.com/github/gh-ost/blob/master/LICENSE
+*/
+
+package mysql
+
+import (
+	"testing"
+
+	"github.com/outbrain/golib/log"
+	test "github.com/outbrain/golib/tests"
+)
+
+func init() {
+	log.SetLevel(log.ERROR)
+}
+
+func TestParseInstanceKey(t *testing.T) {
+	{
+		key, err := ParseInstanceKey("myhost:1234")
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(key.Hostname, "myhost")
+		test.S(t).ExpectEquals(key.Port, 1234)
+	}
+	{
+		key, err := ParseInstanceKey("myhost")
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(key.Hostname, "myhost")
+		test.S(t).ExpectEquals(key.Port, 3306)
+	}
+	{
+		key, err := ParseInstanceKey("10.0.0.3:3307")
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(key.Hostname, "10.0.0.3")
+		test.S(t).ExpectEquals(key.Port, 3307)
+	}
+	{
+		key, err := ParseInstanceKey("10.0.0.3")
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(key.Hostname, "10.0.0.3")
+		test.S(t).ExpectEquals(key.Port, 3306)
+	}
+	{
+		key, err := ParseInstanceKey("[2001:db8:1f70::999:de8:7648:6e8]:3308")
+		test.S(t).ExpectNil(err)
+		test.S(t).ExpectEquals(key.Hostname, "2001:db8:1f70::999:de8:7648:6e8")
+		test.S(t).ExpectEquals(key.Port, 3308)
+	}
+	{
+		_, err := ParseInstanceKey("10.0.0.4:")
+		test.S(t).ExpectNotNil(err)
+	}
+	{
+		_, err := ParseInstanceKey("10.0.0.4:5.6.7")
+		test.S(t).ExpectNotNil(err)
+	}
+}