chore: import upstream snapshot with attribution

Tests/ContainerizationTests/CHInterfaceTests.swift

@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the Containerization 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.
+//===----------------------------------------------------------------------===//
+
+#if os(Linux)
+import CloudHypervisor
+import ContainerizationExtras
+import Testing
+
+@testable import Containerization
+
+@Suite("TAPInterface")
+struct CHInterfaceTests {
+    @Test("chNetConfig populates tap, mac, and mtu and leaves IP fields nil")
+    func chNetConfigShape() throws {
+        let cidr = try CIDRv4("192.168.64.3/24")
+        let gateway = try IPv4Address("192.168.64.1")
+        let mac = try MACAddress("02:42:ac:11:00:02")
+        let iface = TAPInterface(
+            tapName: "tap0",
+            ipv4Address: cidr,
+            ipv4Gateway: gateway,
+            macAddress: mac,
+            mtu: 1500
+        )
+
+        let cfg = try iface.chNetConfig()
+        #expect(cfg.tap == "tap0")
+        #expect(cfg.mac == mac.description)
+        #expect(cfg.mtu == 1500)
+        #expect(cfg.ip == nil)
+        #expect(cfg.mask == nil)
+        #expect(cfg.id == nil)
+    }
+
+    @Test("chNetConfig omits mac when macAddress is nil")
+    func chNetConfigOmitsMac() throws {
+        let cidr = try CIDRv4("10.0.0.5/24")
+        let iface = TAPInterface(tapName: "ch-tap1", ipv4Address: cidr)
+
+        let cfg = try iface.chNetConfig()
+        #expect(cfg.tap == "ch-tap1")
+        #expect(cfg.mac == nil)
+        #expect(cfg.mtu == 1500)
+    }
+
+    @Test("TAPInterface satisfies Interface")
+    func interfaceConformance() throws {
+        let cidr = try CIDRv4("192.168.64.3/24")
+        let iface: any Interface = TAPInterface(tapName: "tap0", ipv4Address: cidr)
+        #expect(iface.ipv4Address == cidr)
+        #expect(iface.ipv4Gateway == nil)
+        #expect(iface.macAddress == nil)
+        #expect(iface.mtu == 1500)
+    }
+}
+#endif