flux diff artifact: Check for an expected error using `errors.Is`.

This fixes the `TestDiffArtifact` unit test.

Signed-off-by: Florian Forster <fforster@gitlab.com>

cmd/flux/diff_artifact.go

@@ -33,6 +33,8 @@ import (
 	"github.com/fluxcd/flux2/v2/internal/flags"
 )
 
+var ErrDiffArtifactChanged = errors.New("the remote and local artifact contents differ")
+
 var diffArtifactCmd = &cobra.Command{
 	Use:   "artifact",
 	Short: "Diff Artifact",
@@ -124,7 +126,7 @@ func diffArtifactCmdRun(cmd *cobra.Command, args []string) error {
 		fmt.Print(diff)
 	}
 
-	return fmt.Errorf("%q and %q differ", ociURL, diffArtifactArgs.path)
+	return fmt.Errorf("%q and %q: %w", ociURL, diffArtifactArgs.path, ErrDiffArtifactChanged)
 }
 
 func diffArtifact(ctx context.Context, client *oci.Client, remoteURL, localPath string) (string, error) {

cmd/flux/diff_artifact_test.go

@@ -81,7 +81,7 @@ func TestDiffArtifact(t *testing.T) {
 			argsTpl:  "diff artifact %s --path=%s",
 			pushFile: "./testdata/diff-artifact/deployment.yaml",
 			diffFile: "./testdata/diff-artifact/deployment-diff.yaml",
-			assert:   assertError("the remote artifact contents differs from the local one"),
+			assert:   assertErrorIs(ErrDiffArtifactChanged),
 		},
 	}
 

cmd/flux/main_test.go

@@ -20,6 +20,7 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -33,7 +34,7 @@ import (
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/mattn/go-shellwords"
-	"k8s.io/apimachinery/pkg/api/errors"
+	k8serrors "k8s.io/apimachinery/pkg/api/errors"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	k8syaml "k8s.io/apimachinery/pkg/util/yaml"
 	"k8s.io/client-go/tools/clientcmd"
@@ -115,7 +116,7 @@ func (m *testEnvKubeManager) CreateObjects(clientObjects []*unstructured.Unstruc
 		obj.SetResourceVersion(createObj.GetResourceVersion())
 		err = m.client.Status().Update(context.Background(), obj)
 		// Updating status of static objects results in not found error.
-		if err != nil && !errors.IsNotFound(err) {
+		if err != nil && !k8serrors.IsNotFound(err) {
 			return err
 		}
 	}
@@ -272,6 +273,15 @@ func assertError(expected string) assertFunc {
 	}
 }
 
+func assertErrorIs(want error) assertFunc {
+	return func(_ string, got error) error {
+		if errors.Is(got, want) {
+			return nil
+		}
+		return fmt.Errorf("Expected error '%v' but got '%v'", want, got)
+	}
+}
+
 // Expect the command to succeed with the expected test output.
 func assertGoldenValue(expected string) assertFunc {
 	return assert(