MVP of a signal messenger test (#230)

* MVP of a signal messenger test

* Add minimal signal test unit tests

* Add Signal test to the im nettest group

* Add test for https://sfu.voip.signal.org/

* Fix bug in client-side determination of blocking status

* Add uptime.signal.org to the test targets

* Add more tests

* Check for invalid CA being passed
* Check that the update function works as expected

* Update internal/engine/experiment/signal/signal_test.go

Co-authored-by: Simone Basso <bassosimone@gmail.com>

* fix: back out URL we shouldn't have changed

When merging probe-engine into probe-cli, we changed too many URLs
and some of them should not have been changed.

I noticed this during the review of Signal and I choose to add
this commit to revert such changes.

While there, make sure the URL of the experiment is OK.

* fix(signal): reach 100% of coverage

Just so that we can focus on areas of the codebase where we need
more coverage, let us avoid missing an easy line to test.

Co-authored-by: Simone Basso <bassosimone@gmail.com>

internal/engine/experiment/signal/signal_test.go

@@ -0,0 +1,129 @@
+package signal_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/apex/log"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/signal"
+	"github.com/ooni/probe-cli/v3/internal/engine/experiment/urlgetter"
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/mockable"
+	"github.com/ooni/probe-cli/v3/internal/engine/model"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/errorx"
+)
+
+func TestNewExperimentMeasurer(t *testing.T) {
+	measurer := signal.NewExperimentMeasurer(signal.Config{})
+	if measurer.ExperimentName() != "signal" {
+		t.Fatal("unexpected name")
+	}
+	if measurer.ExperimentVersion() != "0.2.0" {
+		t.Fatal("unexpected version")
+	}
+}
+
+func TestGood(t *testing.T) {
+	measurer := signal.NewExperimentMeasurer(signal.Config{})
+	measurement := new(model.Measurement)
+	err := measurer.Run(
+		context.Background(),
+		&mockable.Session{
+			MockableLogger: log.Log,
+		},
+		measurement,
+		model.NewPrinterCallbacks(log.Log),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tk := measurement.TestKeys.(*signal.TestKeys)
+	if tk.Agent != "redirect" {
+		t.Fatal("unexpected Agent")
+	}
+	if tk.FailedOperation != nil {
+		t.Fatal("unexpected FailedOperation")
+	}
+	if tk.Failure != nil {
+		t.Fatal("unexpected Failure")
+	}
+	if len(tk.NetworkEvents) <= 0 {
+		t.Fatal("no NetworkEvents?!")
+	}
+	if len(tk.Queries) <= 0 {
+		t.Fatal("no Queries?!")
+	}
+	if len(tk.Requests) <= 0 {
+		t.Fatal("no Requests?!")
+	}
+	if len(tk.TCPConnect) <= 0 {
+		t.Fatal("no TCPConnect?!")
+	}
+	if len(tk.TLSHandshakes) <= 0 {
+		t.Fatal("no TLSHandshakes?!")
+	}
+	if tk.SignalBackendFailure != nil {
+		t.Fatal("unexpected SignalBackendFailure")
+	}
+	if tk.SignalBackendStatus != "ok" {
+		t.Fatal("unexpected SignalBackendStatus")
+	}
+	sk, err := measurer.GetSummaryKeys(measurement)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := sk.(signal.SummaryKeys); !ok {
+		t.Fatal("invalid type for summary keys")
+	}
+}
+
+func TestUpdate(t *testing.T) {
+	tk := signal.NewTestKeys()
+	tk.Update(urlgetter.MultiOutput{
+		Input: urlgetter.MultiInput{
+			Config: urlgetter.Config{Method: "GET"},
+			Target: "https://textsecure-service.whispersystems.org/",
+		},
+		TestKeys: urlgetter.TestKeys{
+			Failure: (func() *string {
+				s := errorx.FailureEOFError
+				return &s
+			})(),
+		},
+	})
+	if tk.SignalBackendStatus != "blocked" {
+		t.Fatal("SignalBackendStatus should be blocked")
+	}
+	if *tk.SignalBackendFailure != errorx.FailureEOFError {
+		t.Fatal("invalid SignalBackendError")
+	}
+}
+
+func TestBadSignalCA(t *testing.T) {
+	measurer := signal.NewExperimentMeasurer(signal.Config{
+		SignalCA: "INVALIDCA",
+	})
+	measurement := new(model.Measurement)
+	err := measurer.Run(
+		context.Background(),
+		&mockable.Session{
+			MockableLogger: log.Log,
+		},
+		measurement,
+		model.NewPrinterCallbacks(log.Log),
+	)
+	if err.Error() != "AppendCertsFromPEM failed" {
+		t.Fatal("not the error we expected")
+	}
+}
+
+func TestGetSummaryInvalidType(t *testing.T) {
+	measurer := signal.Measurer{}
+	in := make(chan int)
+	out, err := measurer.GetSummaryKeys(&model.Measurement{TestKeys: in})
+	if err == nil || err.Error() != "invalid test keys type" {
+		t.Fatal("not the error we expected", err)
+	}
+	if out != nil {
+		t.Fatal("expected nil output here")
+	}
+}