Mock ExchangeDataCollection (#166)

Implements a mock exchange data collection that can be used to test without connecting to graph.

Currently returns a "fixed message" but we can extend this to return anything that implements io.Reader
e.g. a file that contains a serialized message.

src/go.mod

@@ -77,6 +77,7 @@ require (
 	github.com/rs/xid v1.4.0 // indirect
 	github.com/sirupsen/logrus v1.8.1 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
+	github.com/stretchr/objx v0.2.0 // indirect
 	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
 	github.com/zeebo/blake3 v0.2.3 // indirect
 	go.opentelemetry.io/otel v1.7.0 // indirect

src/go.sum

@@ -336,6 +336,8 @@ github.com/spf13/viper v1.12.0 h1:CZ7eSOd3kZoaYDLbXnmzgQI5RlciuXBMA+18HwHRfZQ=
 github.com/spf13/viper v1.12.0/go.mod h1:b6COn30jlNxbm/V2IqWiNWkJ+vZNiMNksliPCiuKtSI=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.1.1/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/objx v0.2.0 h1:Hbg2NidpLE8veEBkEZTL3CvlkUIVzuU9jDplZO54c48=
+github.com/stretchr/objx v0.2.0/go.mod h1:qt09Ya8vawLte6SNmTgCsAVtYtaKzEcn8ATUoHMkEqE=
 github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81PSLYec5m4=

src/internal/connector/mockconnector/mock_data_collection.go

@@ -0,0 +1,63 @@
+package mockconnector
+
+import (
+	"bytes"
+	"io"
+
+	"github.com/google/uuid"
+
+	"github.com/alcionai/corso/internal/connector"
+)
+
+// MockExchangeDataCollection represents a mock exchange mailbox
+type MockExchangeDataCollection struct {
+	fullPath     []string
+	messageCount int
+	messagesRead int
+}
+
+var (
+	_ connector.DataCollection = &MockExchangeDataCollection{}
+	_ connector.DataStream     = &MockExchangeData{}
+)
+
+// NewMockExchangeDataCollection creates an data collection that will return the specified number of
+// mock messages when iterated
+func NewMockExchangeDataCollection(pathRepresentation []string, numMessagesToReturn int) *MockExchangeDataCollection {
+	collection := &MockExchangeDataCollection{
+		fullPath:     pathRepresentation,
+		messageCount: numMessagesToReturn,
+		messagesRead: 0,
+	}
+	return collection
+}
+
+func (medc *MockExchangeDataCollection) FullPath() []string {
+	return append([]string{}, medc.fullPath...)
+}
+
+// NextItem returns either the next item in the collection or an error if one occurred.
+// If not more items are available in the collection, returns (nil, nil).
+func (medc *MockExchangeDataCollection) NextItem() (connector.DataStream, error) {
+	if medc.messagesRead < medc.messageCount {
+		medc.messagesRead++
+		// We can plug in whatever data we want here (can be an io.Reader to a test data file if needed)
+		m := []byte("test message")
+		return &MockExchangeData{uuid.NewString(), bytes.NewReader(m)}, nil
+	}
+	return nil, io.EOF
+}
+
+// ExchangeData represents a single item retrieved from exchange
+type MockExchangeData struct {
+	id     string
+	reader io.Reader
+}
+
+func (med *MockExchangeData) UUID() string {
+	return med.id
+}
+
+func (med *MockExchangeData) ToReader() io.Reader {
+	return med.reader
+}

src/internal/connector/mockconnector/mock_data_collection_test.go

@@ -0,0 +1,33 @@
+package mockconnector_test
+
+import (
+	"io"
+	"io/ioutil"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/suite"
+
+	"github.com/alcionai/corso/internal/connector/mockconnector"
+)
+
+type MockExchangeDataCollectionSuite struct {
+	suite.Suite
+}
+
+func TestMockExchangeDataCollectionSuite(t *testing.T) {
+	suite.Run(t, new(MockExchangeDataCollectionSuite))
+}
+
+func (suite *MockExchangeDataCollectionSuite) TestMockExchangeDataCollection() {
+	mdc := mockconnector.NewMockExchangeDataCollection([]string{"foo", "bar"}, 2)
+
+	messagesRead := 0
+
+	for item, err := mdc.NextItem(); err != io.EOF; item, err = mdc.NextItem() {
+		_, err := ioutil.ReadAll(item.ToReader())
+		assert.NoError(suite.T(), err)
+		messagesRead++
+	}
+	assert.Equal(suite.T(), 2, messagesRead)
+}