add integration test for progress auto fallback

Author: knQzx

Tests/CLITests/Subcommands/Images/TestCLIProgressAuto.swift

@@ -0,0 +1,80 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import Testing
+
+class TestCLIProgressAuto: CLITest {
+    /// When stderr is not a TTY (piped), --progress auto should produce
+    /// plain-text status lines on stderr instead of silence.
+    @Test func testAutoProgressFallsBackToPlainWhenPiped() throws {
+        do {
+            // run() uses Pipe for stderr, so the subprocess sees a non-TTY
+            let (_, _, error, status) = try run(arguments: [
+                "image", "pull",
+                "--progress", "auto",
+                alpine,
+            ])
+            #expect(status == 0, "image pull should succeed, stderr: \(error)")
+            // stderr should contain progress text (not be empty, ignoring the debug warning)
+            let lines = error.components(separatedBy: .newlines)
+                .filter { !$0.contains("Warning! Running debug build") && !$0.isEmpty }
+            #expect(!lines.isEmpty, "expected plain progress output on stderr when piped")
+            // should NOT contain ANSI escape sequences
+            #expect(!error.contains("\u{1B}["), "expected no ANSI escapes in piped output")
+        } catch {
+            Issue.record("failed to test auto progress: \(error)")
+            return
+        }
+    }
+
+    /// Explicit --progress plain should also produce plain output on stderr.
+    @Test func testExplicitPlainProgress() throws {
+        do {
+            let (_, _, error, status) = try run(arguments: [
+                "image", "pull",
+                "--progress", "plain",
+                alpine,
+            ])
+            #expect(status == 0, "image pull --progress plain should succeed, stderr: \(error)")
+            let lines = error.components(separatedBy: .newlines)
+                .filter { !$0.contains("Warning! Running debug build") && !$0.isEmpty }
+            #expect(!lines.isEmpty, "expected plain progress output on stderr")
+            #expect(!error.contains("\u{1B}["), "expected no ANSI escapes with --progress plain")
+        } catch {
+            Issue.record("failed to test plain progress: \(error)")
+            return
+        }
+    }
+
+    /// --progress none should produce no progress output on stderr.
+    @Test func testNoneProgressSuppressesOutput() throws {
+        do {
+            let (_, _, error, status) = try run(arguments: [
+                "image", "pull",
+                "--progress", "none",
+                alpine,
+            ])
+            #expect(status == 0, "image pull --progress none should succeed, stderr: \(error)")
+            let lines = error.components(separatedBy: .newlines)
+                .filter { !$0.contains("Warning! Running debug build") && !$0.isEmpty }
+            #expect(lines.isEmpty, "expected no progress output on stderr with --progress none")
+        } catch {
+            Issue.record("failed to test none progress: \(error)")
+            return
+        }
+    }
+}