test(ContainerResource): unit coverage for RestartPolicy + ContainerCreateOptions Codable

Tests/ContainerResourceTests/RestartPolicyTests.swift

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+//===----------------------------------------------------------------------===//
+// 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
+
+@testable import ContainerResource
+
+/// Unit-level coverage for the wire shape of ``RestartPolicy`` and the
+/// forward-compatibility guarantees of ``ContainerCreateOptions``.
+///
+/// `TestCLIRunRestart` already covers end-to-end behavior against a live
+/// daemon. These tests cover the contract one layer down — JSON shape and
+/// legacy-blob compatibility — so a future contributor cannot regress the
+/// `decodeIfPresent` default without a unit-level red flag.
+struct RestartPolicyTests {
+    // MARK: - RestartPolicy round-trip
+
+    @Test
+    func encodesAsBareString() throws {
+        let data = try JSONEncoder().encode(RestartPolicy.always)
+        let s = String(decoding: data, as: UTF8.self)
+        #expect(s == "\"always\"")
+    }
+
+    @Test
+    func decodesEveryCase() throws {
+        let cases: [RestartPolicy] = [.no, .onFailure, .always]
+        for policy in cases {
+            let data = try JSONEncoder().encode(policy)
+            let decoded = try JSONDecoder().decode(RestartPolicy.self, from: data)
+            #expect(decoded == policy)
+        }
+    }
+
+    @Test
+    func rejectsUnknownString() {
+        // Compose-spec includes `unless-stopped`; this PR deliberately does
+        // not. The decoder must reject it so downstream tooling that emits
+        // a fuller mode set fails loudly instead of silently degrading.
+        let bogus = Data("\"unless-stopped\"".utf8)
+        #expect(throws: DecodingError.self) {
+            try JSONDecoder().decode(RestartPolicy.self, from: bogus)
+        }
+    }
+
+    // MARK: - ContainerCreateOptions forward-compat
+
+    /// `options.json` blobs written by daemon versions that predate
+    /// `restartPolicy` MUST still decode — defaulting to `.no`. This is the
+    /// wire-compatibility invariant the PR description promises and the
+    /// reason ``ContainerCreateOptions/init(from:)`` uses
+    /// `decodeIfPresent`. Removing that default would silently break every
+    /// existing container's `options.json` on disk.
+    @Test
+    func decodesLegacyOptionsWithoutRestartPolicy() throws {
+        let legacy = Data(#"{"autoRemove":false}"#.utf8)
+        let options = try JSONDecoder().decode(ContainerCreateOptions.self, from: legacy)
+        #expect(options.autoRemove == false)
+        #expect(options.restartPolicy == .no)
+    }
+
+    @Test
+    func decodesLegacyOptionsWithAutoRemove() throws {
+        let legacy = Data(#"{"autoRemove":true}"#.utf8)
+        let options = try JSONDecoder().decode(ContainerCreateOptions.self, from: legacy)
+        #expect(options.autoRemove == true)
+        #expect(options.restartPolicy == .no)
+    }
+
+    @Test
+    func roundTripPreservesRestartPolicy() throws {
+        let original = ContainerCreateOptions(autoRemove: false, restartPolicy: .onFailure)
+        let data = try JSONEncoder().encode(original)
+        let decoded = try JSONDecoder().decode(ContainerCreateOptions.self, from: data)
+        #expect(decoded.autoRemove == original.autoRemove)
+        #expect(decoded.restartPolicy == original.restartPolicy)
+    }
+
+    @Test
+    func encodedJSONIncludesRestartPolicyField() throws {
+        let options = ContainerCreateOptions(autoRemove: false, restartPolicy: .always)
+        let data = try JSONEncoder().encode(options)
+        let json = String(decoding: data, as: UTF8.self)
+        #expect(json.contains("\"restartPolicy\":\"always\""))
+    }
+
+    @Test
+    func defaultStaticIsNoRestart() {
+        #expect(ContainerCreateOptions.default.restartPolicy == .no)
+        #expect(ContainerCreateOptions.default.autoRemove == false)
+    }
+}