diff --git a/scripts/presubmit-tests.sh b/scripts/presubmit-tests.sh
index b10a8515cfc..3f15cf3abaf 100755
--- a/scripts/presubmit-tests.sh
+++ b/scripts/presubmit-tests.sh
@@ -43,7 +43,7 @@ IS_DOCUMENTATION_PR=0
 # Returns true if PR only contains the given file regexes.
 # Parameters: $1 - file regexes, space separated.
 function pr_only_contains() {
-  [[ -z "$(echo "${CHANGED_FILES}" | grep -v \(${1// /\\|}\)$))" ]]
+  [[ -z "$(echo "${CHANGED_FILES}" | grep -v "\(${1// /\\|}\)$")" ]]
 }
 
 # List changed files in the current PR.
diff --git a/test/unit/presubmit-tests.sh b/test/unit/presubmit-tests.sh
index 1b2bef809c8..134acb340e3 100755
--- a/test/unit/presubmit-tests.sh
+++ b/test/unit/presubmit-tests.sh
@@ -175,6 +175,55 @@ function test_custom_runners_fail_fast() {
   }
 }
 
+function test_exempt_md() {
+  source $(dirname $0)/../../scripts/presubmit-tests.sh
+
+  function list_changed_files() {
+    echo "README.md"
+    echo "OWNERS"
+    echo "foo.png"
+  }
+  initialize_environment
+  (( IS_DOCUMENTATION_PR )) || test_failed "README.md is documentation"
+  (( ! IS_PRESUBMIT_EXEMPT_PR )) || test_failed "README.md is not exempt"
+}
+
+function test_exempt_no_md() {
+  source $(dirname $0)/../../scripts/presubmit-tests.sh
+
+  function list_changed_files() {
+    echo "OWNERS"
+    echo "AUTHORS"
+  }
+  initialize_environment
+  (( IS_DOCUMENTATION_PR )) || test_failed "OWNERS is considered documentation"
+  (( IS_PRESUBMIT_EXEMPT_PR )) || test_failed "OWNERS is exempt"
+}
+
+function test_exempt_md_code() {
+  source $(dirname $0)/../../scripts/presubmit-tests.sh
+
+  function list_changed_files() {
+    echo "OWNERS"
+    echo "README.md"
+    echo "foo.go"
+  }
+  initialize_environment
+  (( ! IS_DOCUMENTATION_PR )) || test_failed "README.md is documentation"
+  (( ! IS_PRESUBMIT_EXEMPT_PR )) || test_failed "foo.go is not exempt"
+}
+
+function test_exempt_code() {
+  source $(dirname $0)/../../scripts/presubmit-tests.sh
+
+  function list_changed_files() {
+    echo "foo.go"
+  }
+  initialize_environment
+  (( ! IS_DOCUMENTATION_PR )) || test_failed "foo.go is not documentation"
+  (( ! IS_PRESUBMIT_EXEMPT_PR )) || test_failed "foo.go is not exempt"
+}
+
 function run_markdown_build_tests() {
   function list_changed_files() {
     echo "README.md"
@@ -190,6 +239,13 @@ function run_main() {
   main
 }
 
+echo ">> Testing presubmit exempt flow"
+
+test_function ${SUCCESS} "Changed files in commit" call_function_pre test_exempt_md
+test_function ${SUCCESS} "Changed files in commit" call_function_pre test_exempt_no_md
+test_function ${SUCCESS} "Changed files in commit" call_function_pre test_exempt_md_code
+test_function ${SUCCESS} "Changed files in commit" call_function_pre test_exempt_code
+
 echo ">> Testing custom test runners"
 
 test_function ${SUCCESS} "Test passed" call_function_pre test_custom_runners_all run_main