Use the mm version of the dummy file for tests.

PiperOrigin-RevId: 208100213
diff --git a/src/TulsiGeneratorIntegrationTests/BazelFakeWorkspace.swift b/src/TulsiGeneratorIntegrationTests/BazelFakeWorkspace.swift
index 8257207..532f610 100644
--- a/src/TulsiGeneratorIntegrationTests/BazelFakeWorkspace.swift
+++ b/src/TulsiGeneratorIntegrationTests/BazelFakeWorkspace.swift
@@ -92,8 +92,8 @@
   func setup() -> BazelFakeWorkspace? {
     installWorkspaceFile()
     do {
-      try createDummyFile(path: "tools/objc/objc_dummy.m", content: "")
-      try addExportsFiles(buildFilePath: "tools/objc", exportedFile: "objc_dummy.m")
+      try createDummyFile(path: "tools/objc/objc_dummy.mm", content: "")
+      try addExportsFiles(buildFilePath: "tools/objc", exportedFile: "objc_dummy.mm")
     } catch let e as NSError {
       XCTFail("Failed to set up fake workspace. Error: \(e.localizedDescription)")
     }
diff --git a/src/TulsiGeneratorIntegrationTests/Resources/LegacySwift.BUILD b/src/TulsiGeneratorIntegrationTests/Resources/LegacySwift.BUILD
index 980e14a..31d3fed 100644
--- a/src/TulsiGeneratorIntegrationTests/Resources/LegacySwift.BUILD
+++ b/src/TulsiGeneratorIntegrationTests/Resources/LegacySwift.BUILD
@@ -38,7 +38,7 @@
 objc_library(
     name = "ApplicationLibrary",
     srcs = [
-        "//tools/objc:objc_dummy.m",
+        "//tools/objc:objc_dummy.mm",
     ],
     deps = [
         ":SwiftLibrary",
diff --git a/src/TulsiGeneratorIntegrationTests/Resources/Swift.BUILD b/src/TulsiGeneratorIntegrationTests/Resources/Swift.BUILD
index bf000b4..d8cc060 100644
--- a/src/TulsiGeneratorIntegrationTests/Resources/Swift.BUILD
+++ b/src/TulsiGeneratorIntegrationTests/Resources/Swift.BUILD
@@ -35,7 +35,7 @@
 objc_library(
     name = "ApplicationLibrary",
     srcs = [
-        "//tools/objc:objc_dummy.m",
+        "//tools/objc:objc_dummy.mm",
     ],
     deps = [
         ":SwiftLibrary",