diff --git a/bin/git-check-assertions b/bin/git-check-assertions
index ea221fc..9e85abf 100755
--- a/bin/git-check-assertions
+++ b/bin/git-check-assertions
@@ -53,6 +53,15 @@ assert_failure() {
   fi
 }
 assert_output() {
+  if [ "${1:-}" = "--partial" ]; then
+    local expected="$2"
+    if [[ "$output" != *"$expected"* ]]; then
+      echo "Expected output to contain: $expected"
+      echo "Actual output: $output"
+      exit 1
+    fi
+    return 0
+  fi
   if [ "$output" != "$1" ]; then
     echo "Expected output to equal: $1"
     echo "Actual output: $output"
diff --git a/test/git-check-assertions.bats b/test/git-check-assertions.bats
index a6a2bba..697d47d 100755
--- a/test/git-check-assertions.bats
+++ b/test/git-check-assertions.bats
@@ -179,3 +179,23 @@ commit_with_assertion() {
 
   assert_success
 }
+
+@test "assert_output --partial should succeed if output contains the given string" {
+  git checkout -b feature
+  commit_with_assertion $'run echo hello\nassert_output --partial ell'
+
+  run git-check-assertions
+
+  assert_success
+}
+
+@test "assert_output --partial should fail if output does not contain the given string" {
+  git checkout -b feature
+  commit_with_assertion $'run echo hello\nassert_output --partial xyz'
+
+  run git-check-assertions
+
+  assert_failure
+  assert_output --partial "Expected output to contain: xyz"
+  assert_output --partial "Actual output: hello"
+}