Use enum for warmup images. (#1990)

- Closes #1982.
- Makes warmup image code more readable in tests.

Author: jglogan

Sources/ContainerTestSupport/ContainerFixture+ContainerHelpers.swift

@@ -57,7 +57,7 @@ extension ContainerFixture {
         autoRemove: Bool = true,
         containerEnv: [String: String] = [:]
     ) throws {
-        let imageRef = image ?? ContainerFixture.warmupImages[0]
+        let imageRef = image ?? WarmupImage.alpine320.rawValue
         var runArgs = ["run"]
         if autoRemove { runArgs.append("--rm") }
         runArgs += ["--name", name, "-d"]
@@ -78,7 +78,7 @@ extension ContainerFixture {
         networks: [String] = [],
         ports: [String] = []
     ) throws {
-        let imageRef = image ?? ContainerFixture.warmupImages[0]
+        let imageRef = image ?? WarmupImage.alpine320.rawValue
         var createArgs = ["create", "--rm", "--name", name]
         createArgs += proxyEnvironmentArgs
         for v in volumes { createArgs += ["-v", v] }

Sources/ContainerTestSupport/ContainerFixture.swift

@@ -59,16 +59,6 @@ import Testing
 /// pattern the structured helpers don't cover.
 public final class ContainerFixture: Sendable {
 
-    // MARK: - Configuration
-
-    /// Images preloaded by the ``ImageWarmup`` suite before concurrent tests run.
-    /// Add new commonly-used images here; the warmup pass pulls them in parallel.
-    public static let warmupImages: [String] = [
-        "ghcr.io/linuxcontainers/alpine:3.20",
-        "ghcr.io/linuxcontainers/alpine:3.18",
-        "ghcr.io/containerd/busybox:1.36",
-    ]
-
     // MARK: - State
 
     /// Short random identifier prefixed to every resource this test creates.
@@ -249,7 +239,8 @@ public final class ContainerFixture: Sendable {
     /// The returned name is `{testID}-{imageName}:{tag}`, e.g.
     /// `a3f7c2b1-alpine:3.20`. Tests operate freely on this reference;
     /// the canonical warmup image is never touched.
-    public func copyWarmupImage(_ canonical: String) throws -> String {
+    public func copyWarmupImage(_ image: WarmupImage) throws -> String {
+        let canonical = image.rawValue
         let lastComponent = canonical.split(separator: "/").last.map(String.init) ?? canonical
         let parts = lastComponent.split(separator: ":", maxSplits: 1)
         let name = String(parts[0])

Sources/ContainerTestSupport/WarmupImage.swift

@@ -0,0 +1,23 @@
+//===----------------------------------------------------------------------===//
+// 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.
+//===----------------------------------------------------------------------===//
+
+/// Images preloaded by the ``ImageWarmup`` suite before concurrent tests run.
+/// Add new commonly-used images here; the warmup pass pulls them in parallel.
+public enum WarmupImage: String, CaseIterable, Sendable {
+    case alpine320 = "ghcr.io/linuxcontainers/alpine:3.20"
+    case alpine318 = "ghcr.io/linuxcontainers/alpine:3.18"
+    case busybox136 = "ghcr.io/containerd/busybox:1.36"
+}

Tests/IntegrationTests/Build/TestCLIBuilderSerial.swift

@@ -876,7 +876,7 @@ struct TestCLIBuilderSerial {
                 let dir = try f.createTempDir()
                 try f.createContext(
                     dir: dir,
-                    dockerfile: "FROM \(ContainerFixture.warmupImages[0])\nADD emptyFile /",
+                    dockerfile: "FROM \(WarmupImage.alpine320.rawValue)\nADD emptyFile /",
                     context: [.file("emptyFile", content: .zeroFilled(size: 1))])
                 let image = "registry.local/no-cache-pull:\(UUID().uuidString)"
                 try f.buildWithPaths(tags: [image], contextDir: dir, otherArgs: ["--pull", "--no-cache"])

Tests/IntegrationTests/Containers/TestCLICopyCommand.swift

@@ -23,7 +23,7 @@ import Testing
 struct TestCLICreateCommand {
     @Test func testCreateArgsPassthrough() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             try f.doCreate(name: name, image: image, args: ["echo", "-n", "hello", "world"])
             try f.doRemove(name)
@@ -32,7 +32,7 @@ struct TestCLICreateCommand {
 
     @Test func testCreateWithMACAddress() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             let expectedMAC = try MACAddress("02:42:ac:11:00:03")
 
@@ -52,7 +52,7 @@ struct TestCLICreateCommand {
 
     @Test func testPublishPortParserMaxPorts() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             var args: [String] = ["create", "--name", name]
             for i in 0..<64 {
@@ -68,7 +68,7 @@ struct TestCLICreateCommand {
 
     @Test func testPublishPortParserTooManyPorts() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             var args: [String] = ["create", "--name", name]
             for i in 0..<65 {
@@ -84,7 +84,7 @@ struct TestCLICreateCommand {
 
     @Test func testCreateWithFQDNName() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             // Prefix with testID to avoid name collisions; hostname is the first FQDN component.
             let name = "\(f.testID).example.com"
             let expectedHostname = f.testID

Tests/IntegrationTests/Containers/TestCLICreateCommand.swift

@@ -21,7 +21,7 @@ import Testing
 struct TestCLIExecCommand {
     @Test func testCreateExecCommand() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             try f.doCreate(name: name, image: image)
             f.addCleanup { try? f.doStop(name) }
@@ -36,7 +36,7 @@ struct TestCLIExecCommand {
 
     @Test func testExecDetach() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             try f.doCreate(name: name, image: image)
             f.addCleanup { try? f.doStop(name) }
@@ -70,7 +70,7 @@ struct TestCLIExecCommand {
 
     @Test func testExecDetachProcessRunning() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             try f.doCreate(name: name, image: image)
             f.addCleanup { try? f.doStop(name) }
@@ -92,7 +92,7 @@ struct TestCLIExecCommand {
 
     @Test func testExecOnExitingContainer() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             // sh exits immediately in detached mode with no stdin; container stops on its own.
             try f.doLongRun(name: name, image: image, containerArgs: ["sh"], autoRemove: false)

Tests/IntegrationTests/Containers/TestCLIExecCommand.swift

@@ -23,7 +23,7 @@ import Testing
 struct TestCLIExportCommand {
     @Test func testExportCommand() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             try await f.withContainer(image: image, autoRemove: false) { name in
                 let mustBeInImage = "must-be-in-image"
                 try f.doExec(name, cmd: ["sh", "-c", "echo \(mustBeInImage) > /foo"])

Tests/IntegrationTests/Containers/TestCLIExportCommand.swift

@@ -37,7 +37,7 @@ struct TestCLIPruneCommandSerial {
 
     @Test func testContainerPruneStoppedContainers() async throws {
         try await ContainerFixture.with { f in
-            let image = ContainerFixture.warmupImages[0]
+            let image = WarmupImage.alpine320.rawValue
             if try !f.isImagePresent(image) { try f.doPull(image) }
 
             // One running container that must survive the prune.

Tests/IntegrationTests/Containers/TestCLIPruneCommandSerial.swift

@@ -23,7 +23,7 @@ import Testing
 struct TestCLIRemove {
     @Test func testDeleteStopped() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             // create without --rm so the container persists after being stopped
             try f.doCreate(name: name, image: image)
@@ -35,7 +35,7 @@ struct TestCLIRemove {
 
     @Test func testDeleteAlias() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             try f.doCreate(name: name, image: image)
             try f.run(["rm", name]).check("rm alias failed")
@@ -46,7 +46,7 @@ struct TestCLIRemove {
 
     @Test func testDeleteForceRunning() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             try await f.withContainer(image: image) { name in
                 try f.doRemove(name, force: true)
                 let result = try f.run(["inspect", name])
@@ -72,7 +72,7 @@ struct TestCLIRemove {
 
     @Test func testDeleteDuplicateIds() async throws {
         try await ContainerFixture.with { f in
-            let image = try f.copyWarmupImage(ContainerFixture.warmupImages[0])
+            let image = try f.copyWarmupImage(.alpine320)
             let name = "\(f.testID)-c"
             try f.doCreate(name: name, image: image)
             f.addCleanup { try f.doRemoveIfExists(name, force: true, ignoreFailure: true) }