diff --git a/README.md b/README.md
index d3e1cf8..ff7fe44 100644
--- a/README.md
+++ b/README.md
@@ -398,6 +398,11 @@ The rbenv source code is [hosted on
 GitHub](https://github.com/sstephenson/rbenv). It's clean, modular,
 and easy to understand, even if you're not a shell hacker.
 
+Tests are executed using [Bats](https://github.com/sstephenson/bats):
+
+    $ bats test
+    $ bats test/<file>.bats
+
 Please feel free to submit pull requests and file bugs on the [issue
 tracker](https://github.com/sstephenson/rbenv/issues).
 
diff --git a/libexec/rbenv---version b/libexec/rbenv---version
index ba5c562..79cb64d 100755
--- a/libexec/rbenv---version
+++ b/libexec/rbenv---version
@@ -14,8 +14,9 @@ set -e
 
 version="0.4.0"
 
-cd "$RBENV_ROOT"
-git_revision="$(git describe --tags HEAD 2>/dev/null || true)"
-git_revision="${git_revision#v}"
+if cd "$RBENV_ROOT" 2>/dev/null; then
+  git_revision="$(git describe --tags HEAD 2>/dev/null || true)"
+  git_revision="${git_revision#v}"
+fi
 
 echo "rbenv ${git_revision:-$version}"
diff --git a/libexec/rbenv-shims b/libexec/rbenv-shims
index 713ca5a..9a1b055 100755
--- a/libexec/rbenv-shims
+++ b/libexec/rbenv-shims
@@ -11,6 +11,8 @@ if [ "$1" = "--complete" ]; then
   exit
 fi
 
+shopt -s nullglob
+
 for command in "${RBENV_ROOT}/shims/"*; do
   if [ "$1" = "--short" ]; then
     echo "${command##*/}"
diff --git a/test/commands.bats b/test/commands.bats
new file mode 100644
index 0000000..2cac394
--- /dev/null
+++ b/test/commands.bats
@@ -0,0 +1,27 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "commands" {
+  run rbenv-commands
+  assert_success
+  assert_line "init"
+  assert_line "rehash"
+  assert_line "shell"
+  refute_line "sh-shell"
+  assert_line "echo"
+}
+
+@test "commands --sh" {
+  run rbenv-commands --sh
+  assert_success
+  refute_line "init"
+  assert_line "shell"
+}
+
+@test "commands --no-sh" {
+  run rbenv-commands --no-sh
+  assert_success
+  assert_line "init"
+  refute_line "shell"
+}
diff --git a/test/global.bats b/test/global.bats
new file mode 100644
index 0000000..f6dcc3e
--- /dev/null
+++ b/test/global.bats
@@ -0,0 +1,31 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "default" {
+  run rbenv global
+  assert_success
+  assert_output "system"
+}
+
+@test "read RBENV_ROOT/version" {
+  mkdir -p "$RBENV_ROOT"
+  echo "1.2.3" > "$RBENV_ROOT/version"
+  run rbenv-global
+  assert_success
+  assert_output "1.2.3"
+}
+
+@test "set RBENV_ROOT/version" {
+  mkdir -p "$RBENV_ROOT/versions/1.2.3"
+  run rbenv-global "1.2.3"
+  assert_success
+  run rbenv global
+  assert_success "1.2.3"
+}
+
+@test "fail setting invalid RBENV_ROOT/version" {
+  mkdir -p "$RBENV_ROOT"
+  run rbenv-global "1.2.3"
+  assert_failure "rbenv: version \`1.2.3' not installed"
+}
diff --git a/test/libexec/rbenv-echo b/test/libexec/rbenv-echo
new file mode 100755
index 0000000..0a802df
--- /dev/null
+++ b/test/libexec/rbenv-echo
@@ -0,0 +1,2 @@
+#!/usr/bin/env bash
+eval "echo \$$1"
diff --git a/test/local.bats b/test/local.bats
new file mode 100644
index 0000000..5ccdb2b
--- /dev/null
+++ b/test/local.bats
@@ -0,0 +1,53 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+setup() {
+  mkdir -p "${RBENV_TEST_DIR}/myproject"
+  cd "${RBENV_TEST_DIR}/myproject"
+}
+
+@test "no version" {
+  assert [ ! -e "${PWD}/.ruby-version" ]
+  run rbenv-local
+  assert_failure "rbenv: no local version configured for this directory"
+}
+
+@test "local version" {
+  echo "1.2.3" > .ruby-version
+  run rbenv-local
+  assert_success "1.2.3"
+}
+
+@test "ignores version in parent directory" {
+  echo "1.2.3" > .ruby-version
+  mkdir -p "subdir" && cd "subdir"
+  run rbenv-local
+  assert_failure
+}
+
+@test "ignores RBENV_DIR" {
+  echo "1.2.3" > .ruby-version
+  mkdir -p "$HOME"
+  echo "2.0-home" > "${HOME}/.ruby-version"
+  RBENV_DIR="$HOME" run rbenv-local
+  assert_success "1.2.3"
+}
+
+@test "sets local version" {
+  mkdir -p "${RBENV_ROOT}/versions/1.2.3"
+  run rbenv-local 1.2.3
+  assert_success ""
+  assert [ "$(cat .ruby-version)" = "1.2.3" ]
+}
+
+@test "changes local version" {
+  echo "1.0-pre" > .ruby-version
+  mkdir -p "${RBENV_ROOT}/versions/1.2.3"
+  run rbenv-local
+  assert_success "1.0-pre"
+  run rbenv-local 1.2.3
+  assert_success ""
+  run rbenv-local
+  assert_success "1.2.3"
+}
diff --git a/test/prefix.bats b/test/prefix.bats
new file mode 100644
index 0000000..b7afa87
--- /dev/null
+++ b/test/prefix.bats
@@ -0,0 +1,25 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "prefix" {
+  mkdir -p "${RBENV_TEST_DIR}/myproject"
+  cd "${RBENV_TEST_DIR}/myproject"
+  echo "1.2.3" > .ruby-version
+  mkdir -p "${RBENV_ROOT}/versions/1.2.3"
+  run rbenv-prefix
+  assert_success "${RBENV_ROOT}/versions/1.2.3"
+}
+
+@test "prefix for invalid version" {
+  RBENV_VERSION="1.2.3" run rbenv-prefix
+  assert_failure "rbenv: version \`1.2.3' not installed"
+}
+
+@test "prefix for system" {
+  mkdir -p "${RBENV_TEST_DIR}/bin"
+  touch "${RBENV_TEST_DIR}/bin/ruby"
+  chmod +x "${RBENV_TEST_DIR}/bin/ruby"
+  RBENV_VERSION="system" run rbenv-prefix
+  assert_success "$RBENV_TEST_DIR"
+}
diff --git a/test/rbenv.bats b/test/rbenv.bats
new file mode 100644
index 0000000..e8a939a
--- /dev/null
+++ b/test/rbenv.bats
@@ -0,0 +1,47 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "blank invocation" {
+  run rbenv
+  assert_success
+  assert [ "${lines[0]}" = "rbenv 0.4.0" ]
+}
+
+@test "invalid command" {
+  run rbenv does-not-exist
+  assert_failure
+  assert_output "rbenv: no such command \`does-not-exist'"
+}
+
+@test "default RBENV_ROOT" {
+  RBENV_ROOT="" HOME=/home/mislav run rbenv root
+  assert_success
+  assert_output "/home/mislav/.rbenv"
+}
+
+@test "inherited RBENV_ROOT" {
+  RBENV_ROOT=/opt/rbenv run rbenv root
+  assert_success
+  assert_output "/opt/rbenv"
+}
+
+@test "default RBENV_DIR" {
+  run rbenv echo RBENV_DIR
+  assert_output "$(pwd)"
+}
+
+@test "inherited RBENV_DIR" {
+  dir="${BATS_TMPDIR}/myproject"
+  mkdir -p "$dir"
+  RBENV_DIR="$dir" run rbenv echo RBENV_DIR
+  assert_output "$dir"
+}
+
+@test "invalid RBENV_DIR" {
+  dir="${BATS_TMPDIR}/does-not-exist"
+  assert [ ! -d "$dir" ]
+  RBENV_DIR="$dir" run rbenv echo RBENV_DIR
+  assert_failure
+  assert_output "rbenv: cannot change working directory to \`$dir'"
+}
diff --git a/test/rehash.bats b/test/rehash.bats
index 22f26d0..6e9e890 100755
--- a/test/rehash.bats
+++ b/test/rehash.bats
@@ -1,33 +1,27 @@
 #!/usr/bin/env bats
 
-export PATH="${BATS_TEST_DIRNAME}/../libexec:$PATH"
-
-RBENV_TEST_ROOT="${BATS_TMPDIR}/rbenv"
-export RBENV_ROOT="$RBENV_TEST_ROOT"
-
-teardown() {
-  rm -rf "$RBENV_TEST_ROOT"
-}
+load test_helper
 
 @test "empty rehash" {
+  assert [ ! -d "${RBENV_ROOT}/shims" ]
   run rbenv-rehash
-  [ "$status" -eq 0 ]
-  [ -d "${RBENV_TEST_ROOT}/shims" ]
-  rmdir "${RBENV_TEST_ROOT}/shims"
+  assert_success
+  assert [ -d "${RBENV_ROOT}/shims" ]
+  rmdir "${RBENV_ROOT}/shims"
 }
 
-@test "shims directory not writable" {
-  mkdir -p "${RBENV_TEST_ROOT}/shims"
-  chmod -w "${RBENV_TEST_ROOT}/shims"
+@test "non-writable shims directory" {
+  mkdir -p "${RBENV_ROOT}/shims"
+  chmod -w "${RBENV_ROOT}/shims"
   run rbenv-rehash
-  [ "$status" -eq 1 ]
-  [ "$output" = "rbenv: cannot rehash: ${RBENV_TEST_ROOT}/shims isn't writable" ]
+  assert_failure
+  assert_output "rbenv: cannot rehash: ${RBENV_ROOT}/shims isn't writable"
 }
 
 @test "rehash in progress" {
-  mkdir -p "${RBENV_TEST_ROOT}/shims"
-  touch "${RBENV_TEST_ROOT}/shims/.rbenv-shim"
+  mkdir -p "${RBENV_ROOT}/shims"
+  touch "${RBENV_ROOT}/shims/.rbenv-shim"
   run rbenv-rehash
-  [ "$status" -eq 1 ]
-  [ "$output" = "rbenv: cannot rehash: ${RBENV_TEST_ROOT}/shims/.rbenv-shim exists" ]
+  assert_failure
+  assert_output "rbenv: cannot rehash: ${RBENV_ROOT}/shims/.rbenv-shim exists"
 }
diff --git a/test/shell.bats b/test/shell.bats
new file mode 100644
index 0000000..9477898
--- /dev/null
+++ b/test/shell.bats
@@ -0,0 +1,35 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "no shell version" {
+  mkdir -p "${RBENV_TEST_DIR}/myproject"
+  cd "${RBENV_TEST_DIR}/myproject"
+  echo "1.2.3" > .ruby-version
+  RBENV_VERSION="" run rbenv-sh-shell
+  assert_failure "rbenv: no shell-specific version configured"
+}
+
+@test "shell version" {
+  RBENV_VERSION="1.2.3" run rbenv-sh-shell
+  assert_success 'echo "$RBENV_VERSION"'
+}
+
+@test "shell unset" {
+  run rbenv-sh-shell --unset
+  assert_success "unset RBENV_VERSION"
+}
+
+@test "shell change invalid version" {
+  run rbenv-sh-shell 1.2.3
+  assert_failure
+  assert_line "rbenv: version \`1.2.3' not installed"
+  assert_line "return 1"
+}
+
+@test "shell change version" {
+  mkdir -p "${RBENV_ROOT}/versions/1.2.3"
+  run rbenv-sh-shell 1.2.3
+  assert_success 'export RBENV_VERSION="1.2.3"'
+  refute_line "return 1"
+}
diff --git a/test/shims.bats b/test/shims.bats
new file mode 100644
index 0000000..194554a
--- /dev/null
+++ b/test/shims.bats
@@ -0,0 +1,29 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test "no shims" {
+  run rbenv-shims
+  assert_success
+  assert [ -z "$output" ]
+}
+
+@test "shims" {
+  mkdir -p "${RBENV_ROOT}/shims"
+  touch "${RBENV_ROOT}/shims/ruby"
+  touch "${RBENV_ROOT}/shims/irb"
+  run rbenv-shims
+  assert_success
+  assert_line "${RBENV_ROOT}/shims/ruby"
+  assert_line "${RBENV_ROOT}/shims/irb"
+}
+
+@test "shims --short" {
+  mkdir -p "${RBENV_ROOT}/shims"
+  touch "${RBENV_ROOT}/shims/ruby"
+  touch "${RBENV_ROOT}/shims/irb"
+  run rbenv-shims --short
+  assert_success
+  assert_line "irb"
+  assert_line "ruby"
+}
diff --git a/test/test_helper.bash b/test/test_helper.bash
new file mode 100644
index 0000000..7d52e44
--- /dev/null
+++ b/test/test_helper.bash
@@ -0,0 +1,62 @@
+RBENV_TEST_DIR="${BATS_TMPDIR}/rbenv"
+export RBENV_ROOT="${RBENV_TEST_DIR}/root"
+export HOME="${RBENV_TEST_DIR}/home"
+
+unset RBENV_VERSION
+unset RBENV_DIR
+
+export PATH="${RBENV_TEST_DIR}/bin:$PATH"
+export PATH="${BATS_TEST_DIRNAME}/../libexec:$PATH"
+export PATH="${BATS_TEST_DIRNAME}/libexec:$PATH"
+export PATH="${RBENV_ROOT}/shims:$PATH"
+
+teardown() {
+  rm -rf "$RBENV_TEST_DIR"
+}
+
+flunk() {
+  echo "$@" | sed "s:${RBENV_ROOT}:\$RBENV_ROOT:" >&2
+  return 1
+}
+
+assert_success() {
+  if [ "$status" -ne 0 ]; then
+    flunk "command failed with exit status $status"
+  elif [ "$#" -gt 0 ]; then
+    assert_output "$1"
+  fi
+}
+
+assert_failure() {
+  if [ "$status" -eq 0 ]; then
+    flunk "expected failed exit status"
+  elif [ "$#" -gt 0 ]; then
+    assert_output "$1"
+  fi
+}
+
+assert_output() {
+  if [ "$output" != "$1" ]; then
+    flunk "expected: $1"      || true
+    flunk "got:      $output"
+  fi
+}
+
+assert_line() {
+  for line in "${lines[@]}"; do
+    if [ "$line" = "$1" ]; then return 0; fi
+  done
+  flunk "expected line \`$1'"
+}
+
+refute_line() {
+  for line in "${lines[@]}"; do
+    if [ "$line" = "$1" ]; then flunk "expected to not find line \`$line'"; fi
+  done
+}
+
+assert() {
+  if ! "$@"; then
+    flunk "failed: $@"
+  fi
+}