diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 24d2f14..adfc4ee 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -25,6 +25,14 @@ jobs:
         with:
           command: go version
 
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Run ShellSpec
+        run: |
+          curl -fsSL https://git.io/shellspec | sh -s 0.28.1 -p ./tools -y
+          ./tools/lib/shellspec/bin/shellspec
+
   lint:
     runs-on: ubuntu-latest
 
diff --git a/.shellspec b/.shellspec
new file mode 100644
index 0000000..d567ecf
--- /dev/null
+++ b/.shellspec
@@ -0,0 +1,12 @@
+--require spec_helper
+
+## Default kcov (coverage) options
+# --kcov-options "--include-path=. --path-strip-level=1"
+# --kcov-options "--include-pattern=.sh"
+# --kcov-options "--exclude-pattern=/.shellspec,/spec/,/coverage/,/report/"
+
+## Example: Include script "myprog" with no extension
+# --kcov-options "--include-pattern=.sh,myprog"
+
+## Example: Only specified files/directories
+# --kcov-options "--include-pattern=myprog,/lib/"
diff --git a/spec/spec_helper.sh b/spec/spec_helper.sh
new file mode 100644
index 0000000..93f1908
--- /dev/null
+++ b/spec/spec_helper.sh
@@ -0,0 +1,24 @@
+# shellcheck shell=sh
+
+# Defining variables and functions here will affect all specfiles.
+# Change shell options inside a function may cause different behavior,
+# so it is better to set them here.
+# set -eu
+
+# This callback function will be invoked only once before loading specfiles.
+spec_helper_precheck() {
+  # Available functions: info, warn, error, abort, setenv, unsetenv
+  # Available variables: VERSION, SHELL_TYPE, SHELL_VERSION
+  : minimum_version "0.28.1"
+}
+
+# This callback function will be invoked after a specfile has been loaded.
+spec_helper_loaded() {
+  :
+}
+
+# This callback function will be invoked after core modules has been loaded.
+spec_helper_configure() {
+  # Available functions: import, before_each, after_each, before_all, after_all
+  : import 'support/custom_matcher'
+}