awslogs: Add unit test to ensure log line order

Signed-off-by: Samuel Karp <skarp@amazon.com>

daemon/logger/awslogs/cloudwatchlogs_test.go

@@ -4,6 +4,7 @@ import (
 	"errors"
 	"fmt"
 	"net/http"
+	"reflect"
 	"runtime"
 	"strings"
 	"testing"
@@ -625,3 +626,61 @@ func TestCollectBatchMaxTotalBytes(t *testing.T) {
 		t.Errorf("Expected message to be %s but was %s", "B", message[len(message)-1:])
 	}
 }
+
+func TestCollectBatchWithDuplicateTimestamps(t *testing.T) {
+	mockClient := newMockClient()
+	stream := &logStream{
+		client:        mockClient,
+		logGroupName:  groupName,
+		logStreamName: streamName,
+		sequenceToken: aws.String(sequenceToken),
+		messages:      make(chan *logger.Message),
+	}
+	mockClient.putLogEventsResult <- &putLogEventsResult{
+		successResult: &cloudwatchlogs.PutLogEventsOutput{
+			NextSequenceToken: aws.String(nextSequenceToken),
+		},
+	}
+	ticks := make(chan time.Time)
+	newTicker = func(_ time.Duration) *time.Ticker {
+		return &time.Ticker{
+			C: ticks,
+		}
+	}
+
+	go stream.collectBatch()
+
+	times := maximumLogEventsPerPut
+	expectedEvents := []*cloudwatchlogs.InputLogEvent{}
+	timestamp := time.Now()
+	for i := 0; i < times; i++ {
+		line := fmt.Sprintf("%d", i)
+		if i%2 == 0 {
+			timestamp.Add(1 * time.Nanosecond)
+		}
+		stream.Log(&logger.Message{
+			Line:      []byte(line),
+			Timestamp: timestamp,
+		})
+		expectedEvents = append(expectedEvents, &cloudwatchlogs.InputLogEvent{
+			Message:   aws.String(line),
+			Timestamp: aws.Int64(timestamp.UnixNano() / int64(time.Millisecond)),
+		})
+	}
+
+	ticks <- time.Time{}
+	stream.Close()
+
+	argument := <-mockClient.putLogEventsArgument
+	if argument == nil {
+		t.Fatal("Expected non-nil PutLogEventsInput")
+	}
+	if len(argument.LogEvents) != times {
+		t.Errorf("Expected LogEvents to contain %d elements, but contains %d", times, len(argument.LogEvents))
+	}
+	for i := 0; i < times; i++ {
+		if !reflect.DeepEqual(*argument.LogEvents[i], *expectedEvents[i]) {
+			t.Errorf("Expected event to be %v but was %v", *expectedEvents[i], *argument.LogEvents[i])
+		}
+	}
+}