Remove the word middleware (#1067)

* Rename middleware to plugin

first pass; mostly used 'sed', few spots where I manually changed
text.

This still builds a coredns binary.

* fmt error

* Rename AddMiddleware to AddPlugin

* Readd AddMiddleware to remain backwards compat

plugin/pkg/healthcheck/policy_test.go

@@ -0,0 +1,143 @@
+package healthcheck
+
+import (
+	"io/ioutil"
+	"log"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+)
+
+var workableServer *httptest.Server
+
+func TestMain(m *testing.M) {
+	workableServer = httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			// do nothing
+		}))
+	r := m.Run()
+	workableServer.Close()
+	os.Exit(r)
+}
+
+type customPolicy struct{}
+
+func (r *customPolicy) Select(pool HostPool) *UpstreamHost {
+	return pool[0]
+}
+
+func testPool() HostPool {
+	pool := []*UpstreamHost{
+		{
+			Name: workableServer.URL, // this should resolve (healthcheck test)
+		},
+		{
+			Name: "http://shouldnot.resolve", // this shouldn't
+		},
+		{
+			Name: "http://C",
+		},
+	}
+	return HostPool(pool)
+}
+
+func TestRegisterPolicy(t *testing.T) {
+	name := "custom"
+	customPolicy := &customPolicy{}
+	RegisterPolicy(name, func() Policy { return customPolicy })
+	if _, ok := SupportedPolicies[name]; !ok {
+		t.Error("Expected supportedPolicies to have a custom policy.")
+	}
+
+}
+
+// TODO(miek): Disabled for now, we should get out of the habit of using
+// realtime in these tests .
+func testHealthCheck(t *testing.T) {
+	log.SetOutput(ioutil.Discard)
+
+	u := &HealthCheck{
+		Hosts:       testPool(),
+		FailTimeout: 10 * time.Second,
+		Future:      60 * time.Second,
+		MaxFails:    1,
+	}
+
+	u.healthCheck()
+	// sleep a bit, it's async now
+	time.Sleep(time.Duration(2 * time.Second))
+
+	if u.Hosts[0].Down() {
+		t.Error("Expected first host in testpool to not fail healthcheck.")
+	}
+	if !u.Hosts[1].Down() {
+		t.Error("Expected second host in testpool to fail healthcheck.")
+	}
+}
+
+func TestSelect(t *testing.T) {
+	u := &HealthCheck{
+		Hosts:       testPool()[:3],
+		FailTimeout: 10 * time.Second,
+		Future:      60 * time.Second,
+		MaxFails:    1,
+	}
+	u.Hosts[0].OkUntil = time.Unix(0, 0)
+	u.Hosts[1].OkUntil = time.Unix(0, 0)
+	u.Hosts[2].OkUntil = time.Unix(0, 0)
+	if h := u.Select(); h != nil {
+		t.Error("Expected select to return nil as all host are down")
+	}
+	u.Hosts[2].OkUntil = time.Time{}
+	if h := u.Select(); h == nil {
+		t.Error("Expected select to not return nil")
+	}
+}
+
+func TestRoundRobinPolicy(t *testing.T) {
+	pool := testPool()
+	rrPolicy := &RoundRobin{}
+	h := rrPolicy.Select(pool)
+	// First selected host is 1, because counter starts at 0
+	// and increments before host is selected
+	if h != pool[1] {
+		t.Error("Expected first round robin host to be second host in the pool.")
+	}
+	h = rrPolicy.Select(pool)
+	if h != pool[2] {
+		t.Error("Expected second round robin host to be third host in the pool.")
+	}
+	// mark host as down
+	pool[0].OkUntil = time.Unix(0, 0)
+	h = rrPolicy.Select(pool)
+	if h != pool[1] {
+		t.Error("Expected third round robin host to be first host in the pool.")
+	}
+}
+
+func TestLeastConnPolicy(t *testing.T) {
+	pool := testPool()
+	lcPolicy := &LeastConn{}
+	pool[0].Conns = 10
+	pool[1].Conns = 10
+	h := lcPolicy.Select(pool)
+	if h != pool[2] {
+		t.Error("Expected least connection host to be third host.")
+	}
+	pool[2].Conns = 100
+	h = lcPolicy.Select(pool)
+	if h != pool[0] && h != pool[1] {
+		t.Error("Expected least connection host to be first or second host.")
+	}
+}
+
+func TestCustomPolicy(t *testing.T) {
+	pool := testPool()
+	customPolicy := &customPolicy{}
+	h := customPolicy.Select(pool)
+	if h != pool[0] {
+		t.Error("Expected custom policy host to be the first host.")
+	}
+}