Add test source. (#90)

mocks/source.go

@@ -0,0 +1,68 @@
+package mocks
+
+import (
+	"time"
+
+	"github.com/msales/streams/v6"
+)
+
+var _ streams.Source = (*Source)(nil)
+
+// Source is a test source to be used with streams command-level tests.
+// It allows consumption of provided set of messages and counts commits.
+// Once the counted commits reach expected level an exit signal is emitted.
+type Source struct {
+	ch       chan streams.Message
+	exitCh   chan struct{}
+	count    int
+	expected int
+}
+
+// NewSource creates a new test source.
+func NewSource(msgs []streams.Message, expectedCommitCount int) *Source {
+	ch := make(chan streams.Message, len(msgs))
+	exit := make(chan struct{}, 1)
+	for _, msg := range msgs {
+		ch <- msg
+	}
+
+	return &Source{ch: ch, expected: expectedCommitCount, exitCh: exit}
+}
+
+// Consume gets the next record from the Source.
+func (s *Source) Consume() (streams.Message, error) {
+	select {
+	case msg := <-s.ch:
+		return msg.WithMetadata(s, nil), nil
+
+	case <-time.After(100 * time.Millisecond):
+		return streams.NewMessage(nil, nil), nil
+	}
+}
+
+// Commit marks the consumed records as processed.
+// Once the counted commits reach expected level an exit signal is emitted.
+func (s *Source) Commit(interface{}) error {
+	s.count++
+	if s.count == s.expected {
+		s.exitCh <- struct{}{}
+		close(s.exitCh)
+	}
+
+	return nil
+}
+
+// Close closes the Source.
+func (s *Source) Close() error {
+	return nil
+}
+
+// Wait waits until all expected commits are received or a specified timeout occurs.
+func (s *Source) Wait(timeout time.Duration) {
+	select {
+	case <-s.exitCh:
+		return
+	case <-time.After(timeout):
+		return
+	}
+}