diff --git a/libexec/bats b/libexec/bats
index 1f5351c..9a22cfa 100755
--- a/libexec/bats
+++ b/libexec/bats
@@ -20,7 +20,11 @@ abs_dirname() {
 }
 
 expand_path() {
-  echo "$(abs_dirname "$(dirname "$1")")/$(basename "$1")"
+  { cd "$(dirname "$1")" 2>/dev/null
+    local dirname="$PWD"
+    cd "$OLDPWD"
+    echo "$dirname/$(basename "$1")"
+  } || echo "$1"
 }
 
 BATS_LIBEXEC="$(abs_dirname "$0")"
diff --git a/libexec/bats-exec b/libexec/bats-exec
index 3901999..d062732 100755
--- a/libexec/bats-exec
+++ b/libexec/bats-exec
@@ -19,6 +19,15 @@ load() {
   source "$BATS_TEST_DIRNAME/$1.bash"
 }
 
+run() {
+  local e
+  [[ ! "$-" =~ e ]] || e=1
+  set +e
+  output="$("$@" 2>&1)"
+  status="$?"
+  [ -z "$e" ] || set -e
+}
+
 abort() {
   [ "$#" -eq 0 ] || echo error: "$@" >&2
   exit 1
@@ -43,6 +52,7 @@ bats_test_function() {
 }
 
 bats_exit_trap() {
+  trap - err exit
   if [ -z "$BATS_TEST_COMPLETED" ]; then
     echo "not ok $BATS_TEST_NUMBER $BATS_TEST_DESCRIPTION"
     exit 1
diff --git a/test/bats.bats b/test/bats.bats
new file mode 100644
index 0000000..1db9109
--- /dev/null
+++ b/test/bats.bats
@@ -0,0 +1,21 @@
+#!/usr/bin/env bats
+
+FIXTURE_ROOT="$BATS_TEST_DIRNAME/fixtures"
+
+@test "running 'bats' with no arguments prints usage instructions" {
+  run bats
+  [[ $status -eq 1 ]]
+  [[ $output =~ ^usage: ]]
+}
+
+@test "running 'bats' with an invalid filename prints an error" {
+  run bats nonexistent
+  [[ $status -eq 1 ]]
+  [[ $output =~ does\ not\ exist ]]
+}
+
+@test "running 'bats' with an empty test file runs zero tests" {
+  run bats "$FIXTURE_ROOT/empty.bats"
+  [[ $status -eq 0 ]]
+  [[ $output = "1..0" ]]
+}
diff --git a/test/fixtures/empty.bats b/test/fixtures/empty.bats
new file mode 100644
index 0000000..e69de29