test: add unit tests for fallback client

pkg/client/fallback/fallback_test.go

@@ -0,0 +1,119 @@
+package fallback
+
+import (
+	"context"
+	"errors"
+	"testing"
+
+	"github.com/sirupsen/logrus"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/jetstack/version-checker/pkg/api"
+)
+
+// stubClient is a controllable api.ImageClient for exercising fallback behaviour.
+type stubClient struct {
+	name  string
+	tags  []api.ImageTag
+	err   error
+	calls int
+}
+
+func (s *stubClient) Name() string { return s.name }
+
+func (s *stubClient) IsHost(_ string) bool { return true }
+
+func (s *stubClient) RepoImageFromPath(_ string) (string, string) { return "", "" }
+
+func (s *stubClient) Tags(_ context.Context, _, _, _ string) ([]api.ImageTag, error) {
+	s.calls++
+	return s.tags, s.err
+}
+
+func newTestClient(t *testing.T, clients ...api.ImageClient) *Client {
+	t.Helper()
+	c, err := New(context.Background(), logrus.NewEntry(logrus.New()), clients)
+	require.NoError(t, err)
+	return c
+}
+
+func TestName(t *testing.T) {
+	c := newTestClient(t)
+	assert.Equal(t, "fallback", c.Name())
+}
+
+func TestIsHost(t *testing.T) {
+	c := newTestClient(t)
+	assert.True(t, c.IsHost("anything.example.com"))
+}
+
+func TestRepoImageFromPath(t *testing.T) {
+	c := newTestClient(t)
+	repo, image := c.RepoImageFromPath("some/path")
+	assert.Empty(t, repo)
+	assert.Empty(t, image)
+}
+
+func TestTagsFallsBackToNextClient(t *testing.T) {
+	want := []api.ImageTag{{Tag: "v1.2.3", SHA: "sha256:abc"}}
+	first := &stubClient{name: "first", err: errors.New("boom")}
+	second := &stubClient{name: "second", tags: want}
+
+	c := newTestClient(t, first, second)
+	tags, err := c.Tags(context.Background(), "example.com", "repo", "image")
+
+	require.NoError(t, err)
+	assert.Equal(t, want, tags)
+	assert.Equal(t, 1, first.calls)
+	assert.Equal(t, 1, second.calls)
+}
+
+func TestTagsCachesSuccessfulClient(t *testing.T) {
+	want := []api.ImageTag{{Tag: "v1.2.3", SHA: "sha256:abc"}}
+	first := &stubClient{name: "first", err: errors.New("boom")}
+	second := &stubClient{name: "second", tags: want}
+
+	c := newTestClient(t, first, second)
+
+	_, err := c.Tags(context.Background(), "example.com", "repo", "image")
+	require.NoError(t, err)
+
+	_, err = c.Tags(context.Background(), "example.com", "repo", "image")
+	require.NoError(t, err)
+	assert.Equal(t, 1, first.calls)
+	assert.Equal(t, 2, second.calls)
+}
+
+func TestTagsCacheMissFallsBackAgain(t *testing.T) {
+	want := []api.ImageTag{{Tag: "v9.9.9", SHA: "sha256:def"}}
+	first := &stubClient{name: "first", err: errors.New("boom")}
+	second := &stubClient{name: "second", tags: []api.ImageTag{{Tag: "v1.0.0", SHA: "sha256:aaa"}}}
+
+	c := newTestClient(t, first, second)
+
+	_, err := c.Tags(context.Background(), "example.com", "repo", "image")
+	require.NoError(t, err)
+
+	second.err = errors.New("boom")
+	first.err = nil
+	first.tags = want
+
+	tags, err := c.Tags(context.Background(), "example.com", "repo", "image")
+	require.NoError(t, err)
+	assert.Equal(t, want, tags)
+	assert.Equal(t, 2, second.calls)
+	assert.Equal(t, 2, first.calls)
+}
+
+func TestTagsAllClientsFail(t *testing.T) {
+	first := &stubClient{name: "first", err: errors.New("boom")}
+	second := &stubClient{name: "second", err: errors.New("bang")}
+
+	c := newTestClient(t, first, second)
+	tags, err := c.Tags(context.Background(), "example.com", "repo", "image")
+
+	require.Error(t, err)
+	assert.Nil(t, tags)
+	assert.Contains(t, err.Error(), "failed to fetch tags")
+}