diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index df9c27b0cf..f34f1f45b2 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -704,7 +704,7 @@ jobs:
             cmake -B bld -G Ninja \
               -DCMAKE_SYSTEM_NAME=Windows \
               -DCMAKE_C_COMPILER_TARGET="${TRIPLET}" \
-              -DCMAKE_UNITY_BUILD=ON \
+              -DCMAKE_UNITY_BUILD=ON -D_CURL_TESTS_CONCAT=ON \
               -DCURL_WERROR=ON \
               -DCURL_USE_SCHANNEL=ON -DUSE_WIN32_IDN=ON \
               -DCURL_USE_LIBPSL=OFF \
@@ -741,7 +741,7 @@ jobs:
           find . \( -name '*.exe' -o -name '*.dll' -o -name '*.a' \) -print0 | grep -z curl | xargs -0 stat -c '%10s bytes: %n' --
 
       - name: 'build tests'
-        if: ${{ matrix.build == 'cmake' && matrix.compiler != 'clang-tidy' }}  # Save time by skipping this for autotools and clang-tidy
+        if: ${{ matrix.build == 'cmake' }}  # Save time by skipping this for autotools and clang-tidy
         run: |
           if [ "${MATRIX_BUILD}" = 'cmake' ]; then
             cmake --build bld --target testdeps
diff --git a/scripts/mk-unity.pl b/scripts/mk-unity.pl
index e1bd39de6d..014cfe8ece 100755
--- a/scripts/mk-unity.pl
+++ b/scripts/mk-unity.pl
@@ -31,15 +31,23 @@ use strict;
 use warnings;
 
 if(!@ARGV) {
-    die "Usage: $0 [--test <tests>] [--include <include-c-sources>]\n";
+    die "Usage: $0 [--concat [-I<incdir>]] [--test <tests>] [--include <include-c-sources>]\n";
 }
 
 my @src;
 my %include;
 my $in_include = 0;
 my $any_test = 0;
+my $concat = 0;
+my @incpath;
 foreach my $src (@ARGV) {
-    if($src eq "--test") {
+    if($src eq "--concat") {
+        $concat = 1;
+    }
+    elsif($src =~ "^-I") {
+        push @incpath, substr($src, 2);
+    }
+    elsif($src eq "--test") {
         $in_include = 0;
     }
     elsif($src eq "--include") {
@@ -55,9 +63,35 @@ foreach my $src (@ARGV) {
     }
 }
 
+sub include($@) {
+    my $filename = shift;
+    if($concat) {
+        if(! -f $filename) {
+            foreach my $path (@incpath) {
+                my $fullfn = $path . "/" . $filename;
+                if(-f $fullfn) {
+                    $filename = $fullfn;
+                    last;
+                }
+            }
+        }
+        open(my $fh, '<', $filename) or die "Cannot open '$filename': $!";
+        my $content = do { local $/; <$fh> };
+        close $fh;
+        print "#line 1 \"$filename\"\n$content\n";
+    }
+    else {
+        print "#include \"$filename\"\n";
+    }
+}
+
 print "/* !checksrc! disable COPYRIGHT all */\n\n";
 if($any_test) {
-    print "#include \"first.h\"\n\n";
+    if($concat) {
+        print "/* NOLINTBEGIN(readability-duplicate-include) */\n\n";
+    }
+    include("first.h");
+    print "\n";
 }
 
 my $tlist = "";
@@ -65,7 +99,7 @@ my $tlist = "";
 foreach my $src (@src) {
     if($src =~ /([a-z0-9_]+)\.c$/) {
         my $name = $1;
-        print "#include \"$src\"\n";
+        include($src);
         if(not exists $include{$src}) {  # register test entry function
             $tlist .= "  {\"$name\", test_$name},\n";
         }
@@ -73,6 +107,9 @@ foreach my $src (@src) {
 }
 
 if($any_test) {
-    print "\nconst struct entry_s s_entries[] = {\n$tlist  {NULL, NULL}\n};\n";
-    print "\n#include \"first.c\"\n";
+    print "\nconst struct entry_s s_entries[] = {\n$tlist  {NULL, NULL}\n};\n\n";
+    include("first.c");
+    if($concat) {
+        print "/* NOLINTEND(readability-duplicate-include) */\n";
+    }
 }
diff --git a/tests/libtest/CMakeLists.txt b/tests/libtest/CMakeLists.txt
index 6f27b42dfe..c0f7fe1093 100644
--- a/tests/libtest/CMakeLists.txt
+++ b/tests/libtest/CMakeLists.txt
@@ -39,12 +39,16 @@ add_custom_command(OUTPUT "lib1521.c"
 
 list(APPEND TESTS_C "lib1521.c")
 
+if(_CURL_TESTS_CONCAT)
+  set(_mk_unity_extra "--concat" "-I${CMAKE_CURRENT_SOURCE_DIR}")
+endif()
+
 add_custom_command(OUTPUT "${BUNDLE}.c"
-  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl"
+  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" ${_mk_unity_extra}
     --include ${UTILS_C} ${CURLX_C} ${TOOLX_C} --test ${TESTS_C} > "${BUNDLE}.c"
   DEPENDS
     "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" "${CMAKE_CURRENT_SOURCE_DIR}/Makefile.inc"
-    ${FIRST_C} ${UTILS_C} ${CURLX_C} ${TOOLX_C} ${TESTS_C}
+    ${FIRST_C} ${FIRST_H} ${UTILS_C} ${CURLX_C} ${TOOLX_C} ${TESTS_C}
   VERBATIM)
 
 add_executable(${BUNDLE} EXCLUDE_FROM_ALL "${BUNDLE}.c")
@@ -57,6 +61,9 @@ target_include_directories(${BUNDLE} PRIVATE
   "${CMAKE_CURRENT_SOURCE_DIR}"          # for the generated bundle source to find included test sources
 )
 target_compile_definitions(${BUNDLE} PRIVATE ${CURL_DEBUG_MACROS})
-set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF C_CLANG_TIDY "")
+set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF)
 
-curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${UTILS_C} ${TESTS_C})
+if(NOT _CURL_TESTS_CONCAT)
+  set_target_properties(${BUNDLE} PROPERTIES C_CLANG_TIDY "")
+  curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${UTILS_C} ${TESTS_C})
+endif()
diff --git a/tests/server/CMakeLists.txt b/tests/server/CMakeLists.txt
index feb63ed96a..3c83d397d6 100644
--- a/tests/server/CMakeLists.txt
+++ b/tests/server/CMakeLists.txt
@@ -26,12 +26,16 @@
 curl_transform_makefile_inc("Makefile.inc" "${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 include("${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 
+if(_CURL_TESTS_CONCAT)
+  set(_mk_unity_extra "--concat" "-I${CMAKE_CURRENT_SOURCE_DIR}")
+endif()
+
 add_custom_command(OUTPUT "${BUNDLE}.c"
-  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl"
+  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" ${_mk_unity_extra}
     --include ${UTILS_C} ${CURLX_C} ${TOOLX_C} --test ${TESTS_C} > "${BUNDLE}.c"
   DEPENDS
     "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" "${CMAKE_CURRENT_SOURCE_DIR}/Makefile.inc"
-    ${FIRST_C} ${UTILS_C} ${CURLX_C} ${TOOLX_C} ${TESTS_C}
+    ${FIRST_C} ${FIRST_H} ${UTILS_C} ${CURLX_C} ${TOOLX_C} ${TESTS_C}
   VERBATIM)
 
 add_executable(${BUNDLE} EXCLUDE_FROM_ALL "${BUNDLE}.c")
@@ -43,6 +47,9 @@ target_include_directories(${BUNDLE} PRIVATE
   "${PROJECT_SOURCE_DIR}/src"            # for toolx
   "${CMAKE_CURRENT_SOURCE_DIR}"          # for the generated bundle source to find included test sources
 )
-set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF C_CLANG_TIDY "")
+set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF)
 
-curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${UTILS_C} ${TESTS_C})
+if(NOT _CURL_TESTS_CONCAT)
+  set_target_properties(${BUNDLE} PROPERTIES C_CLANG_TIDY "")
+  curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${UTILS_C} ${TESTS_C})
+endif()
diff --git a/tests/tunit/CMakeLists.txt b/tests/tunit/CMakeLists.txt
index b12e9c205f..2ab4f274e6 100644
--- a/tests/tunit/CMakeLists.txt
+++ b/tests/tunit/CMakeLists.txt
@@ -26,12 +26,16 @@
 curl_transform_makefile_inc("Makefile.inc" "${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 include("${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 
+if(_CURL_TESTS_CONCAT)
+  set(_mk_unity_extra "--concat" "-I${CMAKE_CURRENT_SOURCE_DIR}" "-I${PROJECT_SOURCE_DIR}/tests/libtest")
+endif()
+
 add_custom_command(OUTPUT "${BUNDLE}.c"
-  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl"
+  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" ${_mk_unity_extra}
     --test ${TESTS_C} > "${BUNDLE}.c"
   DEPENDS
     "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" "${CMAKE_CURRENT_SOURCE_DIR}/Makefile.inc"
-    ${FIRST_C} ${TESTS_C}
+    ${FIRST_C} ${FIRST_H} ${TESTS_C}
   VERBATIM)
 
 add_executable(${BUNDLE} EXCLUDE_FROM_ALL "${BUNDLE}.c")
@@ -45,6 +49,9 @@ target_include_directories(${BUNDLE} PRIVATE
   "${CMAKE_CURRENT_SOURCE_DIR}"          # for the generated bundle source to find included test sources
 )
 target_compile_definitions(${BUNDLE} PRIVATE ${CURL_DEBUG_MACROS})
-set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF C_CLANG_TIDY "")
+set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF)
 
-curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${TESTS_C})
+if(NOT _CURL_TESTS_CONCAT)
+  set_target_properties(${BUNDLE} PROPERTIES C_CLANG_TIDY "")
+  curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${TESTS_C})
+endif()
diff --git a/tests/unit/CMakeLists.txt b/tests/unit/CMakeLists.txt
index eb402257f3..2692db5ef5 100644
--- a/tests/unit/CMakeLists.txt
+++ b/tests/unit/CMakeLists.txt
@@ -26,12 +26,16 @@
 curl_transform_makefile_inc("Makefile.inc" "${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 include("${CMAKE_CURRENT_BINARY_DIR}/Makefile.inc.cmake")
 
+if(_CURL_TESTS_CONCAT)
+  set(_mk_unity_extra "--concat" "-I${CMAKE_CURRENT_SOURCE_DIR}" "-I${PROJECT_SOURCE_DIR}/tests/libtest")
+endif()
+
 add_custom_command(OUTPUT "${BUNDLE}.c"
-  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl"
+  COMMAND ${PERL_EXECUTABLE} "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" ${_mk_unity_extra}
     --test ${TESTS_C} > "${BUNDLE}.c"
   DEPENDS
     "${PROJECT_SOURCE_DIR}/scripts/mk-unity.pl" "${CMAKE_CURRENT_SOURCE_DIR}/Makefile.inc"
-    ${FIRST_C} ${TESTS_C}
+    ${FIRST_C} ${FIRST_H} ${TESTS_C}
   VERBATIM)
 
 add_executable(${BUNDLE} EXCLUDE_FROM_ALL "${BUNDLE}.c")
@@ -46,9 +50,12 @@ target_include_directories(${BUNDLE} PRIVATE
 )
 # unit tests are small pretend-libcurl-programs, pass BUILDING_LIBCURL to reflect that
 target_compile_definitions(${BUNDLE} PRIVATE ${CURL_DEBUG_MACROS} "BUILDING_LIBCURL")
-set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF C_CLANG_TIDY "")
+set_target_properties(${BUNDLE} PROPERTIES OUTPUT_NAME "${BUNDLE}" PROJECT_LABEL "Test ${BUNDLE}" UNITY_BUILD OFF)
 
-curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${TESTS_C})
-if(TARGET "${BUNDLE}-clang-tidy")
-  add_dependencies("${BUNDLE}-clang-tidy" curlu-unitprotos)
+if(NOT _CURL_TESTS_CONCAT)
+  set_target_properties(${BUNDLE} PROPERTIES C_CLANG_TIDY "")
+  curl_add_clang_tidy_test_target("${BUNDLE}-clang-tidy" ${BUNDLE} ${FIRST_C} ${TESTS_C})
+  if(TARGET "${BUNDLE}-clang-tidy")
+    add_dependencies("${BUNDLE}-clang-tidy" curlu-unitprotos)
+  endif()
 endif()