diff --git a/clang/test/lit.cfg.py b/clang/test/lit.cfg.py
--- a/clang/test/lit.cfg.py
+++ b/clang/test/lit.cfg.py
@@ -25,7 +25,7 @@
 config.test_format = lit.formats.ShTest(not llvm_config.use_lit_shell)
 
 # suffixes: A list of file extensions to treat as test files.
-config.suffixes = ['.c', '.cpp', '.cppm', '.m', '.mm', '.cu',
+config.suffixes = ['.c', '.cpp', '.i', '.cppm', '.m', '.mm', '.cu',
                    '.ll', '.cl', '.s', '.S', '.modulemap', '.test', '.rs', '.ifs']
 
 # excludes: A list of directories to exclude from the testsuite. The 'Inputs'