diff --git a/test/Driver/lit.local.cfg b/test/Driver/lit.local.cfg
new file mode 100644
index 0000000000000..ae6a2606f1b41
--- /dev/null
+++ b/test/Driver/lit.local.cfg
@@ -0,0 +1,2 @@
+if not 'legacy_swift_driver' in config.available_features:
+    config.unsupported = True
diff --git a/test/ModuleInterface/convenience-init-merge-module.swift b/test/ModuleInterface/convenience-init-merge-module.swift
new file mode 100644
index 0000000000000..c58a597659986
--- /dev/null
+++ b/test/ModuleInterface/convenience-init-merge-module.swift
@@ -0,0 +1,44 @@
+// REQUIRES: legacy_swift_driver
+// RUN: %empty-directory(%t)
+
+// Generate the parseable interface of the current file via the merge-modules step
+// RUN: %target-build-swift -no-emit-module-separately -emit-module -o %t/Test.swiftmodule -emit-module-interface-path %t/TestMerge.swiftinterface -module-name Test %s
+
+// Make sure both don't add override for inits shadowing convenience initializers
+// RUN: %FileCheck %s < %t/TestMerge.swiftinterface
+
+// Check we can consume the interface without issue
+// RUN: %target-swift-frontend -swift-version 5 -compile-module-from-interface -o %t/Test.swiftmodule %t/TestMerge.swiftinterface
+
+public class Base {
+  let x: Int
+  public init(x: Int) {
+    self.x = x
+  }
+  convenience public init() {
+    self.init(x: 1)
+  }
+}
+
+public class Derived: Base {
+  // CHECK: {{^}}  public init(z: Swift.Int)
+  public init(z: Int) {
+    super.init(x: z)
+  }
+  // CHECK: {{^}}  public convenience init()
+  convenience public init() {
+    self.init(z: 1)
+  }
+}
+
+public class Derived2: Base {
+  // CHECK: {{^}}  public init()
+  public init() {
+    super.init(x: 1)
+  }
+
+  // CHECK: {{^}}  override public convenience init(x: Swift.Int)
+  override convenience public init(x: Int) {
+    self.init()
+  }
+}
diff --git a/test/ModuleInterface/convenience-init.swift b/test/ModuleInterface/convenience-init.swift
index 0a136d9c221d1..f8a4e63ff7ac8 100644
--- a/test/ModuleInterface/convenience-init.swift
+++ b/test/ModuleInterface/convenience-init.swift
@@ -1,18 +1,13 @@
 // RUN: %empty-directory(%t)
 
-// Generate the parseable interface of the current file via the merge-modules step
-// RUN: %target-build-swift -no-emit-module-separately -emit-module -o %t/Test.swiftmodule -emit-module-interface-path %t/TestMerge.swiftinterface -module-name Test %s
-
 // Generate the parseable interface of the current file via a single frontend invocation
 // RUN: %target-swift-frontend -typecheck  -enable-objc-interop -emit-module-interface-path %t/TestSingle.swiftinterface -module-name Test %s
 
 // Make sure both don't add override for inits shadowing convenience initializers
-// RUN: %FileCheck --check-prefixes=CHECK,SINGLE %s < %t/TestSingle.swiftinterface
-// RUN: %FileCheck --check-prefixes=CHECK,MERGE %s < %t/TestMerge.swiftinterface
+// RUN: %FileCheck --check-prefixes=CHECK %s < %t/TestSingle.swiftinterface
 
 // Check we can consume the interface without issue
 // RUN: %target-swift-frontend -swift-version 5 -compile-module-from-interface -o %t/Test.swiftmodule %t/TestSingle.swiftinterface
-// RUN: %target-swift-frontend -swift-version 5 -compile-module-from-interface -o %t/Test.swiftmodule %t/TestMerge.swiftinterface
 
 public class Base {
   let x: Int
@@ -29,8 +24,7 @@ public class Derived: Base {
   public init(z: Int) {
     super.init(x: z)
   }
-  // MERGE: {{^}}  public convenience init()
-  // SINGLE: {{^}}  convenience public init()
+  // CHECK: {{^}}  convenience public init()
   convenience public init() {
     self.init(z: 1)
   }
@@ -42,8 +36,7 @@ public class Derived2: Base {
     super.init(x: 1)
   }
 
-  // MERGE: {{^}}  override public convenience init(x: Swift.Int)
-  // SINGLE: {{^}}  override convenience public init(x: Swift.Int)
+  // CHECK: {{^}}  override convenience public init(x: Swift.Int)
   override convenience public init(x: Int) {
     self.init()
   }
diff --git a/test/ModuleInterface/enums-layout-merge-module.swift b/test/ModuleInterface/enums-layout-merge-module.swift
new file mode 100644
index 0000000000000..610fad2b26b62
--- /dev/null
+++ b/test/ModuleInterface/enums-layout-merge-module.swift
@@ -0,0 +1,85 @@
+// REQUIRES: legacy_swift_driver
+// RUN: %empty-directory(%t)
+// RUN: %target-build-swift -no-emit-module-separately -emit-module-interface-path %t/Lib.swiftinterface -emit-module -o %t/unused.swiftmodule -enable-library-evolution -Xfrontend -enable-objc-interop -Xfrontend -disable-objc-attr-requires-foundation-module -swift-version 5 %S/Inputs/enums-layout-helper.swift -module-name Lib
+// RUN: %FileCheck -check-prefix CHECK -check-prefix CHECK-MULTI-FILE %S/Inputs/enums-layout-helper.swift < %t/Lib.swiftinterface
+// RUN: %target-swift-frontend -enable-objc-interop -compile-module-from-interface %t/Lib.swiftinterface -o  %t/compiled-from-interface.swiftmodule -module-name Lib
+// RUN: %target-swift-frontend -enable-objc-interop -O -emit-ir -primary-file %s -I %t -Xllvm -swiftmergefunc-threshold=0 | %FileCheck %s
+
+
+import Lib
+
+// CHECK-LABEL: define{{.+}}testFutureproofEnum
+func testFutureproofEnum() -> FutureproofEnum {
+  // Check a few things in the function to make sure it's getting the case
+  // representation dynamically.
+  // CHECK: [[CASE:%.+]] = load i32, ptr @"$s3Lib15FutureproofEnumO1byA2CmFWC"
+  // CHECK: [[METADATA_RESPONSE:%.+]] = tail call swiftcc %swift.metadata_response @"$s3Lib15FutureproofEnumOMa"
+  // CHECK: [[METADATA:%.+]] = extractvalue %swift.metadata_response [[METADATA_RESPONSE]], 0
+  // CHECK: call void {{%.+}}(ptr noalias %0, i32 [[CASE]], ptr [[METADATA]])
+  // CHECK-NEXT: ret void
+  return .b
+} // CHECK-NEXT: {{^}$}}
+
+// CHECK-LABEL: define{{.+}}testFrozenEnum
+func testFrozenEnum() -> FrozenEnum {
+  // CHECK: ret i8 1
+  return .b
+} // CHECK-NEXT: {{^}$}}
+
+// CHECK-LABEL: define{{.+}}testFutureproofObjCEnum
+func testFutureproofObjCEnum() -> FutureproofObjCEnum {
+  // CHECK: ret i{{32|64}} 10
+  return .b
+} // CHECK-NEXT: {{^}$}}
+
+// CHECK-LABEL: define{{.+}}testFrozenObjCEnum
+func testFrozenObjCEnum() -> FrozenObjCEnum {
+  // CHECK: ret i{{32|64}} 10
+  return .b
+} // CHECK-NEXT: {{^}$}}
+
+// CHECK-LABEL: define{{.+}}testFutureproofUnicodeScalarEnum
+func testFutureproofUnicodeScalarEnum() -> FutureproofUnicodeScalarEnum {
+  // CHECK: [[CASE:%.+]] = load i32, ptr @"$s3Lib28FutureproofUnicodeScalarEnumO1ayA2CmFWC"
+  // CHECK: [[METADATA_RESPONSE:%.+]] = tail call swiftcc %swift.metadata_response @"$s3Lib28FutureproofUnicodeScalarEnumOMa"
+  // CHECK: [[METADATA:%.+]] = extractvalue %swift.metadata_response [[METADATA_RESPONSE]], 0
+  // CHECK: call void {{%.+}}(ptr noalias %0, i32 [[CASE]], ptr [[METADATA]])
+  // CHECK-NEXT: ret void
+  return .a
+}
+
+// CHECK-LABEL: define{{.+}}testFutureproofIndirectEnum
+func testFutureproofIndirectEnum() -> FutureproofIndirectEnum {
+  // CHECK: [[CASE:%.+]] = load i32, ptr @"$s3Lib23FutureproofIndirectEnumO1cyA2CmFWC"
+  // CHECK: [[METADATA_RESPONSE:%.+]] = tail call swiftcc %swift.metadata_response @"$s3Lib23FutureproofIndirectEnumOMa"
+  // CHECK: [[METADATA:%.+]] = extractvalue %swift.metadata_response [[METADATA_RESPONSE]], 0
+  // CHECK: call void {{%.+}}(ptr noalias %0, i32 [[CASE]], ptr [[METADATA]])
+  // CHECK-NEXT: ret void
+  return .c
+}
+
+// CHECK-LABEL: define{{.+}}testFrozenIndirectEnum
+func testFrozenIndirectEnum() -> FrozenIndirectEnum {
+  // Whether this is "1" or "2" depends on whether the reserved ObjC tagged
+  // pointer bit is the top or bottom bit on this platform.
+  // CHECK: ret i{{32|64}} {{1|2}}
+  return .c
+}
+
+// CHECK-LABEL: define{{.+}}testFutureproofIndirectCaseEnum
+func testFutureproofIndirectCaseEnum() -> FutureproofIndirectCaseEnum {
+  // CHECK: [[CASE:%.+]] = load i32, ptr @"$s3Lib27FutureproofIndirectCaseEnumO1cyA2CmFWC"
+  // CHECK: [[METADATA_RESPONSE:%.+]] = tail call swiftcc %swift.metadata_response @"$s3Lib27FutureproofIndirectCaseEnumOMa"
+  // CHECK: [[METADATA:%.+]] = extractvalue %swift.metadata_response [[METADATA_RESPONSE]], 0
+  // CHECK: call void {{%.+}}(ptr noalias %0, i32 [[CASE]], ptr [[METADATA]])
+  // CHECK-NEXT: ret void
+  return .c
+}
+
+// CHECK-LABEL: define{{.+}}testFrozenIndirectCaseEnum
+func testFrozenIndirectCaseEnum() -> FrozenIndirectCaseEnum {
+  // Whether this is "1" or "2" depends on whether the reserved ObjC tagged
+  // pointer bit is the top or bottom bit on this platform.
+  // CHECK: ret i{{32|64}} {{1|2}}
+  return .c
+}
diff --git a/test/ModuleInterface/enums-layout.swift b/test/ModuleInterface/enums-layout.swift
index a1c15b189677b..54fcfedf1cfea 100644
--- a/test/ModuleInterface/enums-layout.swift
+++ b/test/ModuleInterface/enums-layout.swift
@@ -1,11 +1,4 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-build-swift -no-emit-module-separately -emit-module-interface-path %t/Lib.swiftinterface -emit-module -o %t/unused.swiftmodule -enable-library-evolution -Xfrontend -enable-objc-interop -Xfrontend -disable-objc-attr-requires-foundation-module -swift-version 5 %S/Inputs/enums-layout-helper.swift -module-name Lib
-// RUN: %FileCheck -check-prefix CHECK -check-prefix CHECK-MULTI-FILE %S/Inputs/enums-layout-helper.swift < %t/Lib.swiftinterface
-// RUN: %target-swift-frontend -enable-objc-interop -compile-module-from-interface %t/Lib.swiftinterface -o  %t/compiled-from-interface.swiftmodule -module-name Lib
-// RUN: %target-swift-frontend -enable-objc-interop -O -emit-ir -primary-file %s -I %t -Xllvm -swiftmergefunc-threshold=0 | %FileCheck %s
-
-// Try again using a single-frontend build.
-// RUN: %empty-directory(%t)
 // RUN: %target-build-swift -whole-module-optimization -emit-module-interface-path %t/Lib.swiftinterface -emit-module -o %t/unused.swiftmodule -enable-library-evolution -Xfrontend -enable-objc-interop -Xfrontend -disable-objc-attr-requires-foundation-module -swift-version 5 %S/Inputs/enums-layout-helper.swift -module-name Lib
 // RUN: %FileCheck -check-prefix CHECK -check-prefix CHECK-SINGLE-FRONTEND %S/Inputs/enums-layout-helper.swift < %t/Lib.swiftinterface
 // RUN: %target-swift-frontend -enable-objc-interop -compile-module-from-interface %t/Lib.swiftinterface -o  %t/compiled-from-interface.swiftmodule -module-name Lib
diff --git a/test/lit.cfg b/test/lit.cfg
index 0b251588f60ae..82d6af76a3f13 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -1021,11 +1021,11 @@ if not 'swift_driver' in lit_config.params:
 config.available_features.add('swift_in_compiler')
 
 # Check if we need to run lit tests using the legacy driver or the new driver
-# The default for existing test runs is to use the legacy driver.
-# The new driver is tested separately.
-if os.environ.get('SWIFT_FORCE_TEST_NEW_DRIVER') is None:
+# The default for existing test runs is to use the new driver.
+if 'SWIFT_FORCE_TEST_OLD_DRIVER' in os.environ:
     config.environment['SWIFT_USE_OLD_DRIVER'] = '1'
     config.environment['SWIFT_AVOID_WARNING_USING_OLD_DRIVER'] = '1'
+    config.available_features.add('legacy_swift_driver')
 
 # Enable benchmark testing when the binary is found (has fully qualified path).
 if config.benchmark_o != 'Benchmark_O':