From b1eb6fd15902e2dcbf2de9f47c618fa6caea16e5 Mon Sep 17 00:00:00 2001
From: Philip Gai <philip-gai@github.com>
Date: Thu, 2 Jul 2026 10:49:31 -0500
Subject: [PATCH] test: add regression and coverage tests for
 ACTIONS_CACHE_MODE

Add JobExtension L0 tests asserting the job-start cache-mode log line is
emitted for each mode and absent when the variable is unset, plus handler
regression tests covering coexistence with ACTIONS_CACHE_SERVICE_V2 and that
baseline runtime env is unaffected when no cache-mode is set.
---
 src/Test/L0/Worker/HandlerL0.cs      | 35 ++++++++++++++++++++
 src/Test/L0/Worker/JobExtensionL0.cs | 49 ++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/src/Test/L0/Worker/HandlerL0.cs b/src/Test/L0/Worker/HandlerL0.cs
index 111bfc524..f04e1b47f 100644
--- a/src/Test/L0/Worker/HandlerL0.cs
+++ b/src/Test/L0/Worker/HandlerL0.cs
@@ -141,6 +141,41 @@ namespace GitHub.Runner.Common.Tests.Worker
             }
         }
 
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task RunAsync_CacheModeCoexistsWithCacheServiceV2()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var environment = await RunNodeScriptActionHandlerAsync(hc, new Dictionary<string, VariableValue>
+                {
+                    { "actions_uses_cache_service_v2", "true" },
+                    { "actions_cache_mode", "read" }
+                });
+
+                Assert.Equal(bool.TrueString, environment["ACTIONS_CACHE_SERVICE_V2"]);
+                Assert.Equal("read", environment["ACTIONS_CACHE_MODE"]);
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task RunAsync_DoesNotAffectRuntimeEnv_WhenCacheModeAbsent()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var environment = await RunNodeScriptActionHandlerAsync(hc, new Dictionary<string, VariableValue>());
+
+                // Baseline runtime env is still exported and cache-mode adds nothing.
+                Assert.Equal("https://pipelines.actions.githubusercontent.com/", environment["ACTIONS_RUNTIME_URL"]);
+                Assert.Equal("token", environment["ACTIONS_RUNTIME_TOKEN"]);
+                Assert.False(environment.ContainsKey("ACTIONS_CACHE_MODE"));
+                Assert.False(environment.ContainsKey("ACTIONS_CACHE_SERVICE_V2"));
+            }
+        }
+
         private async Task<Dictionary<string, string>> RunNodeScriptActionHandlerAsync(TestHostContext hc, IDictionary<string, VariableValue> variables)
         {
             var actionDirectory = Path.Combine(hc.GetDirectory(WellKnownDirectory.Work), Guid.NewGuid().ToString());
diff --git a/src/Test/L0/Worker/JobExtensionL0.cs b/src/Test/L0/Worker/JobExtensionL0.cs
index 7204ff5e9..8dfb7627e 100644
--- a/src/Test/L0/Worker/JobExtensionL0.cs
+++ b/src/Test/L0/Worker/JobExtensionL0.cs
@@ -238,6 +238,55 @@ namespace GitHub.Runner.Common.Tests.Worker
             }
         }
 
+        [Theory]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        [InlineData("read")]
+        [InlineData("none")]
+        [InlineData("write")]
+        [InlineData("write-only")]
+        public async Task InitializeJob_LogsCacheMode_WhenVariableSet(string mode)
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                _message.Variables["actions_cache_mode"] = mode;
+                _jobEc.InitializeJob(_message, _tokenSource.Token);
+
+                var jobExtension = new JobExtension();
+                jobExtension.Initialize(hc);
+
+                _actionManager.Setup(x => x.PrepareActionsAsync(It.IsAny<IExecutionContext>(), It.IsAny<IEnumerable<Pipelines.JobStep>>(), It.IsAny<Guid>()))
+                              .Returns(Task.FromResult(new PrepareResult(new List<JobExtensionRunner>(), new Dictionary<Guid, IActionRunner>())));
+
+                await jobExtension.InitializeJob(_jobEc, _message);
+
+                _jobServerQueue.Verify(
+                    x => x.QueueWebConsoleLine(It.IsAny<Guid>(), It.Is<string>(m => m.Contains($"Actions cache-mode: {mode}")), It.IsAny<long?>()),
+                    Times.Once);
+            }
+        }
+
+        [Fact]
+        [Trait("Level", "L0")]
+        [Trait("Category", "Worker")]
+        public async Task InitializeJob_DoesNotLogCacheMode_WhenVariableAbsent()
+        {
+            using (TestHostContext hc = CreateTestContext())
+            {
+                var jobExtension = new JobExtension();
+                jobExtension.Initialize(hc);
+
+                _actionManager.Setup(x => x.PrepareActionsAsync(It.IsAny<IExecutionContext>(), It.IsAny<IEnumerable<Pipelines.JobStep>>(), It.IsAny<Guid>()))
+                              .Returns(Task.FromResult(new PrepareResult(new List<JobExtensionRunner>(), new Dictionary<Guid, IActionRunner>())));
+
+                await jobExtension.InitializeJob(_jobEc, _message);
+
+                _jobServerQueue.Verify(
+                    x => x.QueueWebConsoleLine(It.IsAny<Guid>(), It.Is<string>(m => m.Contains("Actions cache-mode:")), It.IsAny<long?>()),
+                    Times.Never);
+            }
+        }
+
         [Fact]
         [Trait("Level", "L0")]
         [Trait("Category", "Worker")]