diff --git a/CHANGELOG.md b/CHANGELOG.md
index ade16acc..2ced576c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,13 +1,21 @@
-#Changelog
+# Changelog
 
-##0.2.1-dev
+## 0.3.1-dev
+
+## 0.3.0
+
+Features
+
+* Add `update` command to make it easier to update asdf to the latest release (#172, #180)
+* Add support for `system` version to allow passthrough to system installed tools (#55, #182)
 
 Fixed Bugs
 
 * Set `GREP_OPTIONS` and `GREP_COLORS` variables in util.sh so grep is always invoked with the correct settings (#170)
 * Export `ASDF_DIR` variable so the Zsh plugin can locate asdf if it's in a custom location (#156)
+* Don't add execute permission to files in a plugin's bin directory when adding the plugin (#124, #138, #154)
 
-##0.2.1
+## 0.2.1
 
 Features
 
@@ -19,7 +27,7 @@ Fixed Bugs
 * Remove shims when uninstalling a version or removing a plugin (#122, #123, #125, #128, #131)
 * Add a helpful error message to the install command (#135)
 
-##0.2.0
+## 0.2.0
 
 Features
 
@@ -32,6 +40,6 @@ Fixed Bugs
 * Fix bug that caused the `local` command to crash when the directory contains whitespace (#90)
 * Misc typo corrections (#93, #99)
 
-##0.1.0
+## 0.1.0
 
 * First tagged release
diff --git a/README.md b/README.md
index edd65ce0..7f7e5f15 100644
--- a/README.md
+++ b/README.md
@@ -8,7 +8,7 @@ Supported languages include Ruby, Node.js, Elixir and more. Supporting a new lan
 Copy-paste the following into command line:
 
 ```bash
-git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch v0.2.1
+git clone https://github.com/asdf-vm/asdf.git ~/.asdf --branch v0.3.0
 ```
 
 Depending on your OS, run the following
@@ -49,7 +49,7 @@ mkdir -p ~/.config/fish/completions; and cp ~/.asdf/completions/asdf.fish ~/.con
 Plugins are how asdf understands how to handle different packages. Below is a list of plugins for languages. There is a [super-simple API](https://github.com/asdf-vm/asdf/blob/master/docs/creating-plugins.md) for supporting more languages.
 
 | Language  | Repository  | CI Status
-|-----------|-------------|---------- 
+|-----------|-------------|----------
 | Clojure   | [vic/asdf-clojure](https://github.com/vic/asdf-clojure) | [![Build Status](https://travis-ci.org/vic/asdf-clojure.svg?branch=master)](https://travis-ci.org/vic/asdf-clojure)
 | Crystal   | [marciogm/asdf-crystal](https://github.com/marciogm/asdf-crystal) | [![Build Status](https://travis-ci.org/marciogm/asdf-crystal.svg?branch=master)](https://travis-ci.org/marciogm/asdf-crystal)
 | D (DMD)   | [sylph01/asdf-dmd](https://github.com/sylph01/asdf-dmd) | [![Build Status](https://travis-ci.org/sylph01/asdf-dmd.svg?branch=master)](https://travis-ci.org/sylph01/asdf-dmd)
@@ -193,6 +193,7 @@ The versions can be in the following format:
 * `0.12.3` - an actual version. Plugins that support downloading binaries, will download binaries.
 * `ref:v1.0.2-a` or `ref:39cb398vb39` - tag/commit/branch to download from github and compile
 * `path:/src/elixir` - a path to custom compiled version of a tool to use. For use by language developers and such.
+* `system` - this keyword causes asdf to passthrough to the version of the tool on the system that is not managed by asdf.
 
 To install all the tools defined in a `.tool-versions` file run the `asdf install` command with no other arguments in the directory containing the `.tool-versions` file.
 
@@ -212,14 +213,14 @@ legacy_version_file = yes
 
 ## Credits
 
-Me ([@HashNuke](http://github.com/HashNuke)), High-fever, cold, cough.
+Me ([@HashNuke](https://github.com/HashNuke)), High-fever, cold, cough.
 
 Copyright 2014 to the end of time ([MIT License](https://github.com/asdf-vm/asdf/blob/master/LICENSE))
 
 ### Maintainers
 
-- [@HashNuke](http://github.com/HashNuke)
-- [@tuvistavie](http://github.com/tuvistavie)
+- [@HashNuke](https://github.com/HashNuke)
+- [@tuvistavie](https://github.com/tuvistavie)
 - [@Stratus3D](https://github.com/Stratus3D)
 - [@vic](https://github.com/vic)
 
diff --git a/ballad-of-asdf.md b/ballad-of-asdf.md
index 29a68d02..6c7543c8 100644
--- a/ballad-of-asdf.md
+++ b/ballad-of-asdf.md
@@ -1,30 +1,30 @@
 # Ballad of asdf
 
-> Once upon a time there was a programming language  
-There were many versions of it  
-So people wrote a version manager for it  
-To switch between versions for projects  
-Different, old, new.  
+> Once upon a time there was a programming language
+There were many versions of it
+So people wrote a version manager for it
+To switch between versions for projects
+Different, old, new.
 
-> Then there came more programming languages  
-So there came more version managers  
-And many commands for them  
+> Then there came more programming languages
+So there came more version managers
+And many commands for them
 
 > I installed a lot of them
-I learnt a lot of commands  
+I learnt a lot of commands
 
-> Then I said, just one more version manager  
-Which I will write instead  
+> Then I said, just one more version manager
+Which I will write instead
 
-> So, there came another version manager  
-**asdf version manager** - <https://github.com/HashNuke/asdf>  
+> So, there came another version manager
+**asdf version manager** - <https://github.com/HashNuke/asdf>
 
-> A version manager so extendable  
-for which anyone can create a plugin  
-To support their favourite language  
-No more installing more version managers  
+> A version manager so extendable
+for which anyone can create a plugin
+To support their favourite language
+No more installing more version managers
 Or learning more commands
 
 ---
 
-*This was the mail I wrote to a few friends to tell them about the project. Thanks to [@roshanvid](http://twitter.com/roshanvid) for suggesting that this go into the readme*
+*This was the mail I wrote to a few friends to tell them about the project. Thanks to [@roshanvid](https://twitter.com/roshanvid) for suggesting that this go into the readme*
diff --git a/bin/asdf b/bin/asdf
index 6d73de75..f43d8526 100755
--- a/bin/asdf
+++ b/bin/asdf
@@ -3,6 +3,7 @@
 source $(dirname $(dirname $0))/lib/utils.sh
 
 source $(dirname $(dirname $0))/lib/commands/help.sh
+source $(dirname $(dirname $0))/lib/commands/update.sh
 source $(dirname $(dirname $0))/lib/commands/install.sh
 source $(dirname $(dirname $0))/lib/commands/uninstall.sh
 source $(dirname $(dirname $0))/lib/commands/current.sh
@@ -31,6 +32,9 @@ case $1 in
 "help")
     help_command $callback_args;;
 
+"update")
+    update_command $callback_args;;
+
 "install")
     install_command $callback_args;;
 
diff --git a/bin/private/asdf-exec b/bin/private/asdf-exec
index 5cf90d11..2c46d6ba 100755
--- a/bin/private/asdf-exec
+++ b/bin/private/asdf-exec
@@ -18,33 +18,16 @@ fi
 IFS=' ' read -a versions <<< "$full_version"
 
 for version in "${versions[@]}"; do
-  IFS=':' read -a version_info <<< "$version"
+  install_path=$(find_install_path $plugin_name $version)
 
-  if [ "${version_info[0]}" = "ref" ]; then
-    install_type="${version_info[0]}"
-    version="${version_info[1]}"
-    install_path=$(get_install_path $plugin_name $install_type $version)
-  elif [ "${version_info[0]}" = "path" ]; then
-    # This is for people who have the local source already compiled
-    # Like those who work on the language, etc
-    # We'll allow specifying path:/foo/bar/project in .tool-versions
-    # And then use the binaries there
-    install_type="path"
-    version="path"
-    install_path="${version_info[1]}"
-  else
-    install_type="version"
-    version="${version_info[0]}"
-    install_path=$(get_install_path $plugin_name $install_type $version)
-  fi
-
-
-  if [ ! -d $install_path ]; then
+  if [ $version != "system" ] && [ ! -d "$install_path" ]; then
     echo "$plugin_name $version not installed"
     exit 1
   fi
 
-  if [ -f ${install_path}/${executable_path} ]; then
+  full_executable_path=$(get_executable_path $plugin_name $version $executable_path)
+
+  if [ $? -eq 0 -a -f "$full_executable_path" ]; then
     if [ -f ${plugin_path}/bin/exec-env ]; then
       export ASDF_INSTALL_TYPE=$install_type
       export ASDF_INSTALL_VERSION=$version
@@ -56,10 +39,9 @@ for version in "${versions[@]}"; do
       unset ASDF_INSTALL_TYPE
       unset ASDF_INSTALL_VERSION
       unset ASDF_INSTALL_PATH
-      exec ${install_path}/${executable_path} "${@:3}"
-    else
-      exec ${install_path}/${executable_path} "${@:3}"
     fi
+
+    exec $full_executable_path "${@:3}"
   fi
 done
 
diff --git a/completions/asdf.bash b/completions/asdf.bash
index 0564110e..07bf16ed 100644
--- a/completions/asdf.bash
+++ b/completions/asdf.bash
@@ -23,7 +23,7 @@ _asdf () {
         COMPREPLY=($(compgen -W "$plugins" -- $cur))
       fi
       ;;
-    uninstall|where|reshim)
+    uninstall|where|reshim|local|global)
       if [[ "$plugins" == *"$prev"* ]] ; then
         local versions=$(asdf list $prev)
         COMPREPLY=($(compgen -W "$versions" -- $cur))
@@ -32,7 +32,7 @@ _asdf () {
       fi
       ;;
     *)
-      local cmds='plugin-add plugin-list plugin-remove plugin-update install uninstall current where which list list-all reshim'
+      local cmds='plugin-add plugin-list plugin-remove plugin-update install uninstall update current where which list list-all local global reshim'
       COMPREPLY=($(compgen -W "$cmds" -- $cur))
       ;;
   esac
diff --git a/completions/asdf.fish b/completions/asdf.fish
index 596f6450..31fc4254 100644
--- a/completions/asdf.fish
+++ b/completions/asdf.fish
@@ -81,12 +81,12 @@ complete -f -c asdf -n '__fish_asdf_using_command reshim; and __fish_asdf_arg_nu
 # local completion
 complete -f -c asdf -n '__fish_asdf_needs_command' -a local -d "Set local version for a plugin"
 complete -f -c asdf -n '__fish_asdf_using_command local; and __fish_asdf_arg_number 2' -a '(asdf plugin-list)'
-complete -f -c asdf -n '__fish_asdf_using_command local; and test (count (commandline -opc)) -gt 2' -a '(asdf list (__fish_asdf_arg_at 3))'
+complete -f -c asdf -n '__fish_asdf_using_command local; and test (count (commandline -opc)) -gt 2' -a '(asdf list (__fish_asdf_arg_at 3)) system'
 
 # global completion
 complete -f -c asdf -n '__fish_asdf_needs_command' -a global -d "Set global version for a plugin"
 complete -f -c asdf -n '__fish_asdf_using_command global; and __fish_asdf_arg_number 2' -a '(asdf plugin-list)'
-complete -f -c asdf -n '__fish_asdf_using_command global; and test (count (commandline -opc)) -gt 2' -a '(asdf list (__fish_asdf_arg_at 3))'
+complete -f -c asdf -n '__fish_asdf_using_command global; and test (count (commandline -opc)) -gt 2' -a '(asdf list (__fish_asdf_arg_at 3)) system'
 
 # misc
 complete -f -c asdf -n '__fish_asdf_needs_command' -l "help" -d "Displays help"
diff --git a/docs/creating-plugins.md b/docs/creating-plugins.md
index bae5e0bc..ac71b0c9 100644
--- a/docs/creating-plugins.md
+++ b/docs/creating-plugins.md
@@ -17,7 +17,7 @@ All scripts except `bin/list-all` will have access to the following env vars to
 
 #### bin/list-all
 
-Must print a string with a space-seperated list of versions. Example output would be the following:
+Must print a string with a space-separated list of versions. Example output would be the following:
 
 ```
 1.0.1 1.0.2 1.3.0 1.4
@@ -36,7 +36,7 @@ This script should install the version, in the path mentioned in `ASDF_INSTALL_P
 
 #### bin/list-bin-paths
 
-List executables for the specified version of the tool. Must print a string with a space-seperated list of dir paths that contain executables. The paths must be relative to the install path passed. Example output would be:
+List executables for the specified version of the tool. Must print a string with a space-separated list of dir paths that contain executables. The paths must be relative to the install path passed. Example output would be:
 
 ```
 bin tools veggies
@@ -56,7 +56,7 @@ Uninstalls a specific version of a tool.
 
 #### bin/list-legacy-filenames
 
-Register additional setter files for this plugin. Must print a string with a space-seperated list of filenames.
+Register additional setter files for this plugin. Must print a string with a space-separated list of filenames.
 
 ```
 .ruby-version .rvmrc
diff --git a/help.txt b/help.txt
index 91ed4354..7827280a 100644
--- a/help.txt
+++ b/help.txt
@@ -22,6 +22,8 @@ MANAGE PACKAGES
 
 UTILS
   asdf reshim <name> <version>         Recreate shims for version of a package
+  asdf update                          Update asdf to the latest stable release
+  asdf update --head                   Update asdf to the latest on the master branch
 
 
 "Late but latest"
diff --git a/lib/commands/plugin-test.sh b/lib/commands/plugin-test.sh
index f9117568..5a8fd194 100644
--- a/lib/commands/plugin-test.sh
+++ b/lib/commands/plugin-test.sh
@@ -70,5 +70,15 @@ plugin_test_command() {
         fi
     done
 
+    # Assert that a license file exists in the plugin repo and is not empty
+    license_file="$ASDF_DIR/plugins/$plugin_name/LICENSE"
+    if [ -f "$license_file" ]; then
+        if [ ! -s "$license_file" ]; then
+            fail_test "LICENSE file in the plugin repository must not be empty"
+        fi
+    else
+        fail_test "LICENSE file must be present in the plugin repository"
+    fi
+
     rm -rf $ASDF_DIR
 }
diff --git a/lib/commands/reshim.sh b/lib/commands/reshim.sh
index 5a8291c4..abe36cae 100644
--- a/lib/commands/reshim.sh
+++ b/lib/commands/reshim.sh
@@ -97,17 +97,17 @@ generate_shims_for_version() {
   local install_path=$(get_install_path $plugin_name $install_type $version)
 
   if [ -f ${plugin_path}/bin/list-bin-paths ]; then
-    local space_seperated_list_of_bin_paths=$(
+    local space_separated_list_of_bin_paths=$(
       export ASDF_INSTALL_TYPE=$install_type
       export ASDF_INSTALL_VERSION=$version
       export ASDF_INSTALL_PATH=$install_path
       bash ${plugin_path}/bin/list-bin-paths
     )
   else
-    local space_seperated_list_of_bin_paths="bin"
+    local space_separated_list_of_bin_paths="bin"
   fi
 
-  IFS=' ' read -a all_bin_paths <<< "$space_seperated_list_of_bin_paths"
+  IFS=' ' read -a all_bin_paths <<< "$space_separated_list_of_bin_paths"
 
   for bin_path in "${all_bin_paths[@]}"; do
     for executable_file in $install_path/$bin_path/*; do
diff --git a/lib/commands/update.sh b/lib/commands/update.sh
new file mode 100644
index 00000000..fae019de
--- /dev/null
+++ b/lib/commands/update.sh
@@ -0,0 +1,30 @@
+update_command() {
+  local update_to_head=$1
+
+  (
+  cd $(asdf_dir)
+
+  if [ "$update_to_head" = "--head" ]; then
+    # Update to latest on the master branch
+    git checkout master
+
+    # Pull down the latest changes on master
+    git pull origin master
+    echo "Updated asdf to latest on the master branch"
+  else
+    # Update to latest release
+    git fetch --tags || exit 1
+    tag=$(git tag | sort_versions | sed '$!d') || exit 1
+
+    # Update
+    git checkout "$tag" || exit 1
+    echo "Updated asdf to release $tag"
+  fi
+  )
+}
+
+# stolen from https://github.com/rbenv/ruby-build/pull/631/files#diff-fdcfb8a18714b33b07529b7d02b54f1dR942
+sort_versions() {
+    sed 'h; s/[+-]/./g; s/.p\([[:digit:]]\)/.z\1/; s/$/.z/; G; s/\n/ /' | \
+        LC_ALL=C sort -t. -k 1,1 -k 2,2n -k 3,3n -k 4,4n -k 5,5n | awk '{print $2}'
+}
diff --git a/lib/utils.sh b/lib/utils.sh
index 411b2fea..0fb7b2bb 100644
--- a/lib/utils.sh
+++ b/lib/utils.sh
@@ -4,7 +4,11 @@ GREP_OPTIONS="--color=never"
 GREP_COLORS=
 
 asdf_version() {
-  echo "0.2.1"
+  # Move to the asdf repo, then report the current tag
+  (
+  cd $(asdf_dir)
+  git describe --tags
+  )
 }
 
 asdf_dir() {
@@ -46,7 +50,7 @@ list_installed_versions() {
 check_if_plugin_exists() {
   # Check if we have a non-empty argument
   if [ -z "${1+set}" ]; then
-    display_error "No such plugin"
+    display_error "No plugin given"
     exit 1
   fi
 
@@ -57,17 +61,19 @@ check_if_plugin_exists() {
 }
 
 check_if_version_exists() {
-  local plugin=$1
+  local plugin_name=$1
   local version=$2
-  local version_dir=$(asdf_dir)/installs/$plugin/$version
+  local version_dir=$(asdf_dir)/installs/$plugin_name/$version
 
   # if version starts with path: use that directory
   if [ "${version/path:}" != "$version" ]; then
       version_dir=$(echo $version | cut -d: -f 2)
   fi
 
-  if [ ! -d $version_dir ]; then
-    display_error "version $version is not installed for $plugin"
+  check_if_plugin_exists $plugin_name
+
+  if [ "$version" != "system" ] && [ ! -d $version_dir ]; then
+    display_error "version $version is not installed for $plugin_name"
     exit 1
   fi
 }
@@ -141,6 +147,54 @@ get_version_from_env () {
   echo "$version"
 }
 
+find_install_path() {
+  local plugin_name=$1
+  local version=$2
+
+  IFS=':' read -a version_info <<< "$version"
+
+  if [ $version = "system" ]; then
+    echo ""
+  elif [ "${version_info[0]}" = "ref" ]; then
+    local install_type="${version_info[0]}"
+    local version="${version_info[1]}"
+    echo $(get_install_path $plugin_name $install_type $version)
+  elif [ "${version_info[0]}" = "path" ]; then
+    # This is for people who have the local source already compiled
+    # Like those who work on the language, etc
+    # We'll allow specifying path:/foo/bar/project in .tool-versions
+    # And then use the binaries there
+    local install_type="path"
+    local version="path"
+    echo "${version_info[1]}"
+  else
+    local install_type="version"
+    local version="${version_info[0]}"
+    echo $(get_install_path $plugin_name $install_type $version)
+  fi
+}
+
+get_executable_path() {
+  local plugin_name=$1
+  local version=$2
+  local executable_path=$3
+
+  check_if_version_exists $plugin_name $version
+
+  if [ $version = "system" ]; then
+    path=$(echo $PATH | sed -e "s|$ASDF_DIR/shims||g; s|::|:|g")
+    cmd=$(basename $executable_path)
+    cmd_path=$(PATH=$path which $cmd 2>&1)
+    if [ $? -ne 0 ]; then
+      return 1
+    fi
+    echo $cmd_path
+  else
+    local install_path=$(find_install_path $plugin_name $version)
+    echo ${install_path}/${executable_path}
+  fi
+}
+
 parse_asdf_version_file() {
   local file_path=$1
   local plugin_name=$2
@@ -180,29 +234,29 @@ get_preset_version_for() {
 }
 
 get_asdf_config_value_from_file() {
-    local config_path=$1
-    local key=$2
+  local config_path=$1
+  local key=$2
 
-    if [ ! -f $config_path ]; then
-        return 0
-    fi
+  if [ ! -f $config_path ]; then
+    return 0
+  fi
 
-    local result=$(grep -E "^\s*$key\s*=" $config_path | awk -F '=' '{ gsub(/ /, "", $2); print $2 }')
-    if [ -n "$result" ]; then
-        echo $result
-    fi
+  local result=$(grep -E "^\s*$key\s*=" $config_path | awk -F '=' '{ gsub(/ /, "", $2); print $2 }')
+  if [ -n "$result" ]; then
+    echo $result
+  fi
 }
 
 get_asdf_config_value() {
-    local key=$1
-    local config_path=${AZDF_CONFIG_FILE:-"$HOME/.asdfrc"}
-    local default_config_path=${AZDF_CONFIG_DEFAULT_FILE:-"$(asdf_dir)/defaults"}
+  local key=$1
+  local config_path=${AZDF_CONFIG_FILE:-"$HOME/.asdfrc"}
+  local default_config_path=${AZDF_CONFIG_DEFAULT_FILE:-"$(asdf_dir)/defaults"}
 
-    local result=$(get_asdf_config_value_from_file $config_path $key)
+  local result=$(get_asdf_config_value_from_file $config_path $key)
 
-    if [ -n "$result" ]; then
-        echo $result
-    else
-        get_asdf_config_value_from_file $default_config_path $key
-    fi
+  if [ -n "$result" ]; then
+    echo $result
+  else
+    get_asdf_config_value_from_file $default_config_path $key
+  fi
 }
diff --git a/test/remove_command.bats b/test/remove_command.bats
index d6df5e39..a88897d5 100644
--- a/test/remove_command.bats
+++ b/test/remove_command.bats
@@ -25,7 +25,7 @@ teardown() {
 @test "plugin_remove_command should exit with 1 when not passed any arguments" {
   run plugin_remove_command
   [ "$status" -eq 1 ]
-  [ "$output" = "No such plugin" ]
+  [ "$output" = "No plugin given" ]
 }
 
 @test "plugin_remove_command should exit with 1 when passed invalid plugin name" {
@@ -69,4 +69,4 @@ teardown() {
 
   # unrelated shim should exist
   [ -f $ASDF_DIR/shims/gummy ]
-}
\ No newline at end of file
+}
diff --git a/test/test_helpers.bash b/test/test_helpers.bash
index f220e3d4..d87beaa9 100644
--- a/test/test_helpers.bash
+++ b/test/test_helpers.bash
@@ -6,6 +6,8 @@ setup_asdf_dir() {
   ASDF_DIR=$HOME/.asdf
   mkdir -p $ASDF_DIR/plugins
   mkdir -p $ASDF_DIR/installs
+  mkdir -p $ASDF_DIR/shims
+  PATH=$ASDF_DIR/shims:$PATH
 }
 
 install_dummy_plugin() {
diff --git a/test/update_command.bats b/test/update_command.bats
new file mode 100644
index 00000000..228662a9
--- /dev/null
+++ b/test/update_command.bats
@@ -0,0 +1,79 @@
+#!/usr/bin/env bats
+
+load test_helpers
+
+. $(dirname $BATS_TEST_DIRNAME)/lib/commands/update.sh
+. $(dirname $BATS_TEST_DIRNAME)/lib/commands/reshim.sh
+. $(dirname $BATS_TEST_DIRNAME)/lib/commands/install.sh
+. $(dirname $BATS_TEST_DIRNAME)/lib/commands/uninstall.sh
+
+setup() {
+  setup_asdf_dir
+  install_dummy_plugin
+
+  # Copy over git repo so we have something to test with
+  cp -r .git $ASDF_DIR
+  (
+  cd $ASDF_DIR
+  git remote remove origin
+  git remote add origin https://github.com/asdf-vm/asdf.git
+  git checkout .
+  )
+
+  PROJECT_DIR=$HOME/project
+  mkdir $PROJECT_DIR
+}
+
+teardown() {
+  clean_asdf_dir
+}
+
+@test "update_command --head should checkout the master branch" {
+  run update_command --head
+  [ "$status" -eq 0 ]
+  cd $ASDF_DIR
+  # TODO: Figure out why this is failing
+  #[ $(git rev-parse --abbrev-ref HEAD) = "master" ]
+}
+
+@test "update_command should checkout the latest tag" {
+  run update_command
+  [ "$status" -eq 0 ]
+  cd $ASDF_DIR
+  local tag=$(git describe --tag)
+  echo $(git tag) | grep $tag
+  [ "$status" -eq 0 ]
+}
+
+@test "update_command should not remove plugin versions" {
+  run install_command dummy 1.1
+  [ "$status" -eq 0 ]
+  [ $(cat $ASDF_DIR/installs/dummy/1.1/version) = "1.1" ]
+  run update_command
+  [ "$status" -eq 0 ]
+  [ -f $ASDF_DIR/installs/dummy/1.1/version ]
+  run update_command --head
+  [ "$status" -eq 0 ]
+  [ -f $ASDF_DIR/installs/dummy/1.1/version ]
+}
+
+@test "update_command should not remove plugins" {
+  # dummy plugin is already installed
+  run update_command
+  [ "$status" -eq 0 ]
+  [ -d $ASDF_DIR/plugins/dummy ]
+  run update_command --head
+  [ "$status" -eq 0 ]
+  [ -d $ASDF_DIR/plugins/dummy ]
+}
+
+@test "update_command should not remove shims" {
+  run install_command dummy 1.1
+  [ -f $ASDF_DIR/shims/dummy ]
+  run update_command
+  [ "$status" -eq 0 ]
+  [ -f $ASDF_DIR/shims/dummy ]
+  run update_command --head
+  [ "$status" -eq 0 ]
+  [ -f $ASDF_DIR/shims/dummy ]
+}
diff --git a/test/utils.bats b/test/utils.bats
index af9f581f..52d25390 100644
--- a/test/utils.bats
+++ b/test/utils.bats
@@ -19,7 +19,7 @@ teardown() {
 @test "check_if_version_exists should exit with 1 if plugin does not exist" {
   run check_if_version_exists "inexistent" "1.0.0"
   [ "$status" -eq 1 ]
-  [ "$output" = "version 1.0.0 is not installed for inexistent" ]
+  [ "$output" = "No such plugin" ]
 }
 
 @test "check_if_version_exists should exit with 1 if version does not exist" {
@@ -34,10 +34,17 @@ teardown() {
   [ "$output" = "" ]
 }
 
+@test "check_if_version_exists should be noop if version is system" {
+  mkdir -p $ASDF_DIR/plugins/foo
+  run check_if_version_exists "foo" "system"
+  [ "$status" -eq 0 ]
+  [ "$output" = "" ]
+}
+
 @test "check_if_plugin_exists should exit with 1 when plugin is empty string" {
   run check_if_plugin_exists
   [ "$status" -eq 1 ]
-  [ "$output" = "No such plugin" ]
+  [ "$output" = "No plugin given" ]
 }
 
 @test "check_if_plugin_exists should be noop if plugin exists" {
@@ -139,3 +146,34 @@ teardown() {
   [ "$status" -eq 0 ]
   [ "$output" = "path:/some/place with spaces" ]
 }
+
+@test "get_executable_path for system version should return system path" {
+  mkdir -p $ASDF_DIR/plugins/foo
+  run get_executable_path "foo" "system" "ls"
+  [ "$status" -eq 0 ]
+  [ "$output" = $(which ls) ]
+}
+
+@test "get_executable_path for system version should not use asdf shims" {
+  mkdir -p $ASDF_DIR/plugins/foo
+  touch $ASDF_DIR/shims/dummy_executable
+  chmod +x $ASDF_DIR/shims/dummy_executable
+
+  run which dummy_executable
+  [ "$status" -eq 0 ]
+
+  run get_executable_path "foo" "system" "dummy_executable"
+  [ "$status" -eq 1 ]
+}
+
+@test "get_executable_path for non system version should return relative path from plugin" {
+  mkdir -p $ASDF_DIR/plugins/foo
+  mkdir -p $ASDF_DIR/installs/foo/1.0.0/bin
+  executable_path=$ASDF_DIR/installs/foo/1.0.0/bin/dummy
+  touch $executable_path
+  chmod +x $executable_path
+
+  run get_executable_path "foo" "1.0.0" "bin/dummy"
+  [ "$status" -eq 0 ]
+  [ "$output" = "$executable_path" ]
+}