engine: implement loading measurement from []byte (#100)

Required to implement resubmission.

experiment.go

@@ -210,6 +210,19 @@ func (e *Experiment) Measure(input string) (*Measurement, error) {
 	return &Measurement{m: measurement}, err
 }
 
+// LoadMeasurement loads a measurement from a byte stream. The measurement
+// must be a measurement for this experiment.
+func (e *Experiment) LoadMeasurement(data []byte) (*Measurement, error) {
+	var measurement model.Measurement
+	if err := json.Unmarshal(data, &measurement); err != nil {
+		return nil, err
+	}
+	if measurement.TestName != e.Name() {
+		return nil, errors.New("not a measurement for this experiment")
+	}
+	return &Measurement{m: measurement}, nil
+}
+
 // SubmitAndUpdateMeasurement submits a measurement and updates the
 // fields whose value has changed as part of the submission.
 func (e *Experiment) SubmitAndUpdateMeasurement(measurement *Measurement) error {
@@ -284,6 +297,7 @@ var experimentsByName = map[string]func(*Session) *ExperimentBuilder{
 				return example.NewExperiment(session.session, *config.(*example.Config))
 			},
 			config: &example.Config{
+				Message:   "Good day from the example experiment!",
 				SleepTime: int64(2 * time.Second),
 			},
 			needsInput: false,

experiment_test.go

@@ -2,6 +2,8 @@ package engine
 
 import (
 	"errors"
+	"fmt"
+	"io/ioutil"
 	"testing"
 
 	"github.com/ooni/probe-engine/experiment/example"
@@ -344,3 +346,55 @@ func TestSetOption(t *testing.T) {
 		}
 	})
 }
+
+func TestLoadMeasurement(t *testing.T) {
+	sess := newSessionForTesting(t)
+	builder, err := sess.NewExperimentBuilder("example")
+	if err != nil {
+		t.Fatal(err)
+	}
+	experiment := builder.Build()
+	testflow := func(t *testing.T, name string) (*Measurement, error) {
+		path := fmt.Sprintf(
+			"testdata/loadable-measurement-%s.jsonl", name,
+		)
+		data, err := ioutil.ReadFile(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return experiment.LoadMeasurement(data)
+	}
+	t.Run("with correct name", func(t *testing.T) {
+		measurement, err := testflow(t, "example")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if measurement == nil {
+			t.Fatal("expected non nil measurement here")
+		}
+	})
+	t.Run("with invalid name", func(t *testing.T) {
+		measurement, err := testflow(t, "wrongname")
+		if err == nil {
+			t.Fatal("expected error here")
+		}
+		if measurement != nil {
+			t.Fatal("expected nil measurement here")
+		}
+		if err.Error() != "not a measurement for this experiment" {
+			t.Fatal("unexpected error value")
+		}
+	})
+	t.Run("with invalid JSON", func(t *testing.T) {
+		measurement, err := testflow(t, "notjson")
+		if err == nil {
+			t.Fatal("expected error here")
+		}
+		if measurement != nil {
+			t.Fatal("expected nil measurement here")
+		}
+		if err.Error() == "not a measurement for this experiment" {
+			t.Fatal("unexpected error value")
+		}
+	})
+}

testdata/loadable-measurement-example.jsonl

@@ -0,0 +1 @@
+{"data_format_version":"0.2.1","measurement_start_time":"2019-10-28 12:51:07","test_runtime":2.00335395,"probe_asn":"AS30722","probe_cc":"IT","probe_ip":"127.0.0.1","report_id":"20191028T125107Z_AS30722_Hq2A17CsJ3HbCcA7DsVgjLRDbm52YD72RV8jnsV4PAwW4Yay8G","resolver_ip":"172.217.33.129","software_name":"miniooni","software_version":"0.1.0-dev","test_keys":{"success":true},"test_name":"example","test_start_time":"2019-10-28 12:51:06","test_version":"0.0.1"}

testdata/loadable-measurement-notjson.jsonl

@@ -0,0 +1 @@
+{"data_format_version":"0.2.1","measurement_start_time":"2019-10-28 12:51:07","test_runtime":2.00335395,"probe_asn":"AS30722","probe_cc":"IT","probe_ip":"127.0.0.1","report_id":"20191028T125107Z_AS30722_Hq2A17CsJ3HbCcA7DsVgjLRDbm52YD72RV8jnsV4PAwW4Yay8G","resolver_ip":"172.217.33.129","software_name":"miniooni","software_version":"0.1.0-dev","test_keys":{"success":true},"test_name":"example","test_start_time":"2019-10-28 12:51:06","test_version":"0.0.1"

testdata/loadable-measurement-wrongname.jsonl

@@ -0,0 +1 @@
+{"data_format_version":"0.2.1","measurement_start_time":"2019-10-28 12:51:07","test_runtime":2.00335395,"probe_asn":"AS30722","probe_cc":"IT","probe_ip":"127.0.0.1","report_id":"20191028T125107Z_AS30722_Hq2A17CsJ3HbCcA7DsVgjLRDbm52YD72RV8jnsV4PAwW4Yay8G","resolver_ip":"172.217.33.129","software_name":"miniooni","software_version":"0.1.0-dev","test_keys":{"success":true},"test_name":"wrongname","test_start_time":"2019-10-28 12:51:06","test_version":"0.0.1"}