fix: cli test assumes a network interface exists in every sandbox

A runner with no usable interface exits non-zero by design, which the
non-tty test treated as a failure. It now requires a diagnostic naming
the collector or the interface before it skips, so a crash or garbage
output still fails. Also stops the test matrix cancelling the other
platforms on the first failure.

Author: programmersd21

.github/workflows/ci.yml

@@ -33,6 +33,9 @@ jobs:
 
   test:
     strategy:
+      # Run every platform even if one fails: on a cross-platform TUI, a
+      # fail-fast matrix hides the platform that actually broke.
+      fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}

cmd/flow/cli_test.go

@@ -216,16 +216,34 @@ func TestCLITiny(t *testing.T) {
 func TestCLINonTTYDefaultsToTiny(t *testing.T) {
 	// No TTY and no output flag: must not block on the TUI.
 	got := runCLI(t, 20*time.Second)
+
 	if got.exitCode != 0 {
-		t.Fatalf("exit = %d, stderr: %s", got.exitCode, got.stderr)
+		// A sandboxed runner may have no usable interface, in which case a
+		// clean non-zero exit with a diagnostic is the correct behaviour.
+		// Require that diagnostic to name the problem, so a crash or garbage
+		// output still fails rather than hiding behind the skip.
+		msg := strings.TrimSpace(got.stderr)
+		switch {
+		case msg == "":
+			t.Fatalf("exit = %d with empty stderr, want a diagnostic", got.exitCode)
+		case !strings.Contains(msg, "interface") && !strings.Contains(msg, "collector"):
+			t.Fatalf("exit = %d with unexpected stderr %q, want a collector diagnostic",
+				got.exitCode, msg)
+		}
+		t.Skipf("no usable interface here: %s", msg)
 	}
+
 	line := strings.TrimSpace(got.stdout)
 	if !strings.Contains(line, "↓") {
-		t.Errorf("non-TTY run should print the single-line form, got %q", line)
+		t.Errorf("non-TTY run should print the single-line form, got %q (stderr %q)",
+			line, got.stderr)
 	}
-	if strings.Count(line, "\n") > 0 {
+	if strings.Contains(line, "\n") {
 		t.Errorf("non-TTY output should be a single line, got %q", line)
 	}
+	if strings.Contains(line, "\x1b[") {
+		t.Error("non-TTY output must not contain escape codes")
+	}
 }
 
 func TestCLIBitsAffectsUnits(t *testing.T) {