Print the expected char with the default output

cmd/tests/cmd_run_test.go

@@ -57,6 +57,7 @@ func TestSimpleTestStdin(t *testing.T) {
 	cmd.ExecuteWithGlobalState(ts.GlobalState)
 
 	stdout := ts.Stdout.String()
+	assert.Contains(t, stdout, "output: -")
 	assert.Contains(t, stdout, "default: 1 iterations for each of 1 VUs")
 	assert.Contains(t, stdout, "1 complete and 0 interrupted iterations")
 	assert.Empty(t, ts.Stderr.Bytes())
@@ -1745,3 +1746,37 @@ func TestBrowserPermissions(t *testing.T) {
 		})
 	}
 }
+
+func TestUIRenderOutput(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		outputs   []string
+		expRender string
+	}{
+		{outputs: []string{}, expRender: "output: -\n"},
+		{outputs: []string{"json"}, expRender: "output: json(stdout)\n\n"},
+		{outputs: []string{"json", "csv"}, expRender: "output: json(stdout), csv (file.csv)\n\n"},
+	}
+
+	for _, tc := range tests {
+		tc := tc
+
+		t.Run(tc.expRender, func(t *testing.T) {
+			t.Parallel()
+
+			ts := NewGlobalTestState(t)
+			ts.CmdArgs = []string{"k6", "run"}
+			for _, o := range tc.outputs {
+				ts.CmdArgs = append(ts.CmdArgs, "-o")
+				ts.CmdArgs = append(ts.CmdArgs, o)
+			}
+			ts.CmdArgs = append(ts.CmdArgs, "-")
+			ts.Stdin = bytes.NewBufferString(`export default function() {};`)
+			cmd.ExecuteWithGlobalState(ts.GlobalState)
+
+			stdout := ts.Stdout.String()
+			assert.Contains(t, stdout, tc.expRender)
+		})
+	}
+}

cmd/ui.go

@@ -19,6 +19,7 @@ import (
 	"go.k6.io/k6/cmd/state"
 	"go.k6.io/k6/lib"
 	"go.k6.io/k6/lib/consts"
+	"go.k6.io/k6/metrics/engine"
 	"go.k6.io/k6/output"
 	"go.k6.io/k6/ui/pb"
 )
@@ -109,11 +110,16 @@ func printExecutionDescription(
 	switch {
 	case outputOverride != "":
 		outputDescriptions = []string{outputOverride}
-	case len(outputs) == 0:
-		outputDescriptions = []string{"-"}
 	default:
 		for _, out := range outputs {
-			outputDescriptions = append(outputDescriptions, out.Description())
+			desc := out.Description()
+			if desc == engine.IngesterDescription {
+				if len(outputs) != 1 {
+					continue
+				}
+				desc = "-"
+			}
+			outputDescriptions = append(outputDescriptions, desc)
 		}
 	}
 

metrics/engine/ingester.go

@@ -11,6 +11,11 @@ const collectRate = 50 * time.Millisecond
 
 var _ output.Output = &outputIngester{}
 
+// IngesterDescription is a short description for ingester.
+// This variable is used from a function in cmd/ui file for matching this output
+// and print a special text.
+const IngesterDescription = "Internal Metrics Ingester"
+
 // outputIngester implements the output.Output interface and can be used to
 // "feed" the MetricsEngine data from a `k6 run` test run.
 type outputIngester struct {
@@ -23,7 +28,7 @@ type outputIngester struct {
 
 // Description returns a human-readable description of the output.
 func (oi *outputIngester) Description() string {
-	return "engine"
+	return IngesterDescription
 }
 
 // Start the engine by initializing a new output.PeriodicFlusher