refactor(sessionresolver): adapt to changing network conditions (#238)

* feat(sessionresolver): try many and use what works

* fix(sessionresolver): make sure we can use quic

* fix: the config struct is unnecessary

* fix: make kvstore optional

* feat: write simple integration test

* feat: start adding tests

* feat: continue writing tests

* fix(sessionresolver): add more unit tests

* fix(sessionresolver): finish adding tests

* refactor(sessionresolver): changes after code review

internal/engine/internal/sessionresolver/resolvermaker_test.go

@@ -0,0 +1,124 @@
+package sessionresolver
+
+import (
+	"errors"
+	"strings"
+	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/bytecounter"
+)
+
+func TestDefaultByteCounter(t *testing.T) {
+	reso := &Resolver{}
+	bc := reso.byteCounter()
+	if bc == nil {
+		t.Fatal("expected non-nil byte counter")
+	}
+}
+
+func TestDefaultLogger(t *testing.T) {
+	logger := &log.Logger{}
+	reso := &Resolver{Logger: logger}
+	lo := reso.logger()
+	if lo != logger {
+		t.Fatal("expected another logger here counter")
+	}
+}
+
+func TestGetResolverHTTPSStandard(t *testing.T) {
+	bc := bytecounter.New()
+	URL := "https://dns.google"
+	re := &FakeResolver{}
+	cmk := &fakeDNSClientMaker{reso: re}
+	reso := &Resolver{dnsClientMaker: cmk, ByteCounter: bc}
+	out, err := reso.getresolver(URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out != re {
+		t.Fatal("not the result we expected")
+	}
+	o2, err := reso.getresolver(URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out != o2 {
+		t.Fatal("not the result we expected")
+	}
+	reso.closeall()
+	if re.Closed != true {
+		t.Fatal("was not closed")
+	}
+	if cmk.savedURL != URL {
+		t.Fatal("not the URL we expected")
+	}
+	if cmk.savedConfig.ByteCounter != bc {
+		t.Fatal("unexpected ByteCounter")
+	}
+	if cmk.savedConfig.BogonIsError != true {
+		t.Fatal("unexpected BogonIsError")
+	}
+	if cmk.savedConfig.HTTP3Enabled != false {
+		t.Fatal("unexpected HTTP3Enabled")
+	}
+	if cmk.savedConfig.Logger != log.Log {
+		t.Fatal("unexpected Log")
+	}
+}
+
+func TestGetResolverHTTP3(t *testing.T) {
+	bc := bytecounter.New()
+	URL := "http3://dns.google"
+	re := &FakeResolver{}
+	cmk := &fakeDNSClientMaker{reso: re}
+	reso := &Resolver{dnsClientMaker: cmk, ByteCounter: bc}
+	out, err := reso.getresolver(URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out != re {
+		t.Fatal("not the result we expected")
+	}
+	o2, err := reso.getresolver(URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if out != o2 {
+		t.Fatal("not the result we expected")
+	}
+	reso.closeall()
+	if re.Closed != true {
+		t.Fatal("was not closed")
+	}
+	if cmk.savedURL != strings.Replace(URL, "http3://", "https://", 1) {
+		t.Fatal("not the URL we expected")
+	}
+	if cmk.savedConfig.ByteCounter != bc {
+		t.Fatal("unexpected ByteCounter")
+	}
+	if cmk.savedConfig.BogonIsError != true {
+		t.Fatal("unexpected BogonIsError")
+	}
+	if cmk.savedConfig.HTTP3Enabled != true {
+		t.Fatal("unexpected HTTP3Enabled")
+	}
+	if cmk.savedConfig.Logger != log.Log {
+		t.Fatal("unexpected Log")
+	}
+}
+
+func TestGetResolverInvalidURL(t *testing.T) {
+	bc := bytecounter.New()
+	URL := "http3://dns.google"
+	errMocked := errors.New("mocked error")
+	cmk := &fakeDNSClientMaker{err: errMocked}
+	reso := &Resolver{dnsClientMaker: cmk, ByteCounter: bc}
+	out, err := reso.getresolver(URL)
+	if !errors.Is(err, errMocked) {
+		t.Fatal("not the error we expected", err)
+	}
+	if out != nil {
+		t.Fatal("not the result we expected")
+	}
+}