diff --git a/test/ClangImporter/pch-bridging-header.swift b/test/ClangImporter/pch-bridging-header.swift
index 851e069f004..2371547337c 100644
--- a/test/ClangImporter/pch-bridging-header.swift
+++ b/test/ClangImporter/pch-bridging-header.swift
@@ -7,11 +7,13 @@
 // RUN: %target-typecheck-verify-swift -import-objc-header %t/sdk-bridging-header.pch
 
 // Now test the driver-automated version is inert when disabled
-// RUN: env TMPDIR=%t/tmp/ %target-swiftc_driver -typecheck -disable-bridging-pch -save-temps %s -import-objc-header %S/Inputs/sdk-bridging-header.h
+// Output path of the PCH differs in the new driver, so force SWIFT_USE_OLD_DRIVER for now.
+// RUN: env TMPDIR=%t/tmp/ SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -typecheck -disable-bridging-pch -save-temps %s -import-objc-header %S/Inputs/sdk-bridging-header.h
 // RUN: not ls %t/tmp/*.pch >/dev/null 2>&1
 
 // Test the driver-automated version works by default
-// RUN: env TMPDIR=%t/tmp/ %target-swiftc_driver -typecheck -save-temps %s -import-objc-header %S/Inputs/sdk-bridging-header.h
+// Output path of the PCH differs in the new driver, so force SWIFT_USE_OLD_DRIVER for now.
+// RUN: env TMPDIR=%t/tmp/ SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -typecheck -save-temps %s -import-objc-header %S/Inputs/sdk-bridging-header.h
 // RUN: ls %t/tmp/*.pch >/dev/null 2>&1
 // RUN: llvm-objdump --raw-clang-ast %t/tmp/*.pch | llvm-bcanalyzer -dump | %FileCheck %s
 // CHECK: ORIGINAL_FILE{{.*}}Inputs/sdk-bridging-header.h
diff --git a/test/DebugInfo/file_compilation_dir.swift b/test/DebugInfo/file_compilation_dir.swift
index 8d029751ad0..d0c8e93ab24 100644
--- a/test/DebugInfo/file_compilation_dir.swift
+++ b/test/DebugInfo/file_compilation_dir.swift
@@ -6,10 +6,11 @@
 // RUN: mkdir -p %t
 // RUN: cd %t
 // RUN: cp %s .
-// RUN: %target-swiftc_driver -g \
+// Output paths differ in the new driver, so force SWIFT_USE_OLD_DRIVER for now.
+// RUN: env SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -g \
 // RUN:   -c -file-compilation-dir /path/to \
 // RUN:   file_compilation_dir.swift -o - -emit-ir | %FileCheck --check-prefix=CHECK-REL %s
-// RUN: %target-swiftc_driver -g \
+// RUN: env SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -g \
 // RUN:   -c -file-compilation-dir . \
 // RUN:   file_compilation_dir.swift -o - -emit-ir | %FileCheck --check-prefix=CHECK-REL-CWD %s
 
diff --git a/test/Misc/stats_dir_failure_count.swift b/test/Misc/stats_dir_failure_count.swift
index d771991301f..7e678cbd147 100644
--- a/test/Misc/stats_dir_failure_count.swift
+++ b/test/Misc/stats_dir_failure_count.swift
@@ -1,7 +1,7 @@
 // Check that a failed process-tree emits nonzero failure counters
 // RUN: %empty-directory(%t)
 // RUN: echo zzz >%t/other.swift
-// RUN: not %target-swiftc_driver -continue-building-after-errors -D BROKEN -j 2 -typecheck -stats-output-dir %t %s %t/other.swift
+// RUN: not env SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -continue-building-after-errors -D BROKEN -j 2 -typecheck -stats-output-dir %t %s %t/other.swift
 // RUN: %{python} %utils/process-stats-dir.py --set-csv-baseline %t/stats.csv %t
 // RUN: %FileCheck -input-file %t/stats.csv -check-prefix=FAILURE %s
 // FAILURE: {{"Driver.NumProcessFailures"	1$}}
diff --git a/test/Misc/stats_dir_plausible_maxrss.swift b/test/Misc/stats_dir_plausible_maxrss.swift
index a579a8eb266..362407d2148 100644
--- a/test/Misc/stats_dir_plausible_maxrss.swift
+++ b/test/Misc/stats_dir_plausible_maxrss.swift
@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: touch %t/main.swift
-// RUN: %target-swiftc_driver -o %t/main -module-name main -stats-output-dir %t %t/main.swift
+// RUN: env SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -o %t/main -module-name main -stats-output-dir %t %t/main.swift
 // RUN: %{python} %utils/process-stats-dir.py --set-csv-baseline %t/frontend.csv %t
 // RUN: %FileCheck -input-file %t/frontend.csv %s
 
diff --git a/test/ModuleInterface/print_package_name_in_non_package_interface.swift b/test/ModuleInterface/print_package_name_in_non_package_interface.swift
index b743b9f3177..511b44ba0a9 100644
--- a/test/ModuleInterface/print_package_name_in_non_package_interface.swift
+++ b/test/ModuleInterface/print_package_name_in_non_package_interface.swift
@@ -51,7 +51,10 @@
 // RUN: rm -rf %t/Bar.package.swiftinterface
 
 /// Print -package-name in public or private interface.
-// RUN: %target-build-swift -emit-module %t/Bar.swift -I %t \
+/// Note the order of arguments differs across old/new driver, so force old
+/// driver for now.
+// RUN: env SWIFT_USE_OLD_DRIVER=1 %target-build-swift \
+// RUN:   -emit-module %t/Bar.swift -I %t \
 // RUN:   -module-name Bar -package-name barpkg \
 // RUN:   -enable-library-evolution -swift-version 6 \
 // RUN:   -Xfrontend -print-package-name-in-non-package-interface \
diff --git a/test/Serialization/search-paths-relative.swift b/test/Serialization/search-paths-relative.swift
index 1b673196fb4..398562d1b2d 100644
--- a/test/Serialization/search-paths-relative.swift
+++ b/test/Serialization/search-paths-relative.swift
@@ -4,7 +4,8 @@
 // RUN: %empty-directory(%t/Frameworks/has_alias.framework/Modules/has_alias.swiftmodule)
 // RUN: %target-swift-frontend -emit-module -o %t/Frameworks/has_alias.framework/Modules/has_alias.swiftmodule/%target-swiftmodule-name %S/Inputs/alias.swift -module-name has_alias
 
-// RUN: cd %t/secret && %target-swiftc_driver -emit-module -o %t/has_xref.swiftmodule -I . -F ../Frameworks -parse-as-library %S/Inputs/has_xref.swift %S/../Inputs/empty.swift -Xfrontend -serialize-debugging-options -Xcc -ivfsoverlay -Xcc %S/../Inputs/unextended-module-overlay.yaml -Xcc -DDUMMY
+// Output paths differ in the new driver, so force SWIFT_USE_OLD_DRIVER for now.
+// RUN: cd %t/secret && env SWIFT_USE_OLD_DRIVER=1 %target-swiftc_driver -emit-module -o %t/has_xref.swiftmodule -I . -F ../Frameworks -parse-as-library %S/Inputs/has_xref.swift %S/../Inputs/empty.swift -Xfrontend -serialize-debugging-options -Xcc -ivfsoverlay -Xcc %S/../Inputs/unextended-module-overlay.yaml -Xcc -DDUMMY
 // RUN: %target-swift-frontend %s -typecheck -I %t
 
 // Ensure that in Swift 6 mode we do not read out search paths, thus are no longer able to