diff --git a/bin/git-check-assertions b/bin/git-check-assertions
index cdc14e8..ea221fc 100755
--- a/bin/git-check-assertions
+++ b/bin/git-check-assertions
@@ -35,7 +35,7 @@ export -f assert_fails
 # helper functions inspired by bats/bats-assert
 run() {
   set +e
-  ("$@")
+  output="$("$@" 2>&1)"
   status=$?
   set -e
   return 0
@@ -52,7 +52,14 @@ assert_failure() {
     exit 1
   fi
 }
-export -f run assert_success assert_failure
+assert_output() {
+  if [ "$output" != "$1" ]; then
+    echo "Expected output to equal: $1"
+    echo "Actual output: $output"
+    exit 1
+  fi
+}
+export -f run assert_success assert_failure assert_output
 
 # main flow
 orig_ref="$(git symbolic-ref --quiet --short HEAD || git rev-parse HEAD)"
diff --git a/test/git-check-assertions.bats b/test/git-check-assertions.bats
index 064341f..11f23e7 100755
--- a/test/git-check-assertions.bats
+++ b/test/git-check-assertions.bats
@@ -150,3 +150,23 @@ commit_with_assertion() {
   assert_failure
   assert_output --partial "Expected command to fail, but it succeeded."
 }
+
+@test "assert_output should succeed if the output matches the given string" {
+  git checkout -b feature
+  commit_with_assertion $'run echo hello\nassert_output hello'
+
+  run git-check-assertions
+
+  assert_success
+}
+
+@test "assert_output should fail if the output does not match the given string" {
+  git checkout -b feature
+  commit_with_assertion $'run echo hello\nassert_output goodbye'
+
+  run git-check-assertions
+
+  assert_failure
+  assert_output --partial "Expected output to equal: goodbye"
+  assert_output --partial "Actual output: hello"
+}