diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index cd4e3ee..10c72e9 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -22,5 +22,8 @@ jobs:
         ruby-version: '${{ matrix.ruby }}'
         bundler-cache: true
 
+    - name: Install zsh
+      run: sudo apt install -y zsh
+
     - name: Run tests
       run: bundle exec rspec
diff --git a/lib/completely/templates/tester-template.erb b/lib/completely/templates/tester-template.erb
index 85749a5..bcd9223 100644
--- a/lib/completely/templates/tester-template.erb
+++ b/lib/completely/templates/tester-template.erb
@@ -1,7 +1,14 @@
 #!/usr/bin/env bash
+if [[ -n $ZSH_VERSION ]]; then
+  autoload -U +X bashcompinit && bashcompinit
+  autoload -U +X compinit && compinit
+fi
+
+# === COMPLETION SCRIPT START ===
+
 <%= script || %Q[source "#{absolute_script_path}"] %>
 
-# END OF COMPLETION SCRIPT
+# === COMPLETION SCRIPT END ===
 
 COMP_WORDS=( <%= compline %> )
 COMP_LINE="<%= compline %>"
diff --git a/spec/README.md b/spec/README.md
new file mode 100644
index 0000000..25343ef
--- /dev/null
+++ b/spec/README.md
@@ -0,0 +1,32 @@
+# Completely Specs
+
+## Running tests
+
+```bash
+$ rspec
+# or
+$ run spec
+# or, to run just tests in a given file
+$ run spec zsh
+# or, to run just specs tagged with :focus
+$ run spec :focus
+```
+
+You might need to prefix the commands with `bundle exec`, depending on the way
+Ruby is installed.
+
+## Interactive Approvals
+
+Some tests may prompt you for an interactive approval of changes. This
+functionality is provided by the [rspec_approvals gem][1].
+
+Be sure to only approve changes that are indeed expected.
+
+
+## ZSH Compatibility Test
+
+ZSH compatibility test is done by running the completely tester script inside a
+zsh container. This is all done automatically by `spec/completely/zsh_spec.rb`.
+
+
+[1]: https://github.com/dannyben/rspec_approvals
\ No newline at end of file
diff --git a/spec/approvals/tester/script b/spec/approvals/tester/script
index a1c46a9..327178b 100644
--- a/spec/approvals/tester/script
+++ b/spec/approvals/tester/script
@@ -1,7 +1,14 @@
 #!/usr/bin/env bash
+if [[ -n $ZSH_VERSION ]]; then
+  autoload -U +X bashcompinit && bashcompinit
+  autoload -U +X compinit && compinit
+fi
+
+# === COMPLETION SCRIPT START ===
+
 # some completion script
 
-# END OF COMPLETION SCRIPT
+# === COMPLETION SCRIPT END ===
 
 COMP_WORDS=( cli co )
 COMP_LINE="cli co"
diff --git a/spec/approvals/tester/script_path b/spec/approvals/tester/script_path
index 5b98250..6c39f1c 100644
--- a/spec/approvals/tester/script_path
+++ b/spec/approvals/tester/script_path
@@ -1,7 +1,14 @@
 #!/usr/bin/env bash
+if [[ -n $ZSH_VERSION ]]; then
+  autoload -U +X bashcompinit && bashcompinit
+  autoload -U +X compinit && compinit
+fi
+
+# === COMPLETION SCRIPT START ===
+
 source "<path removed>"
 
-# END OF COMPLETION SCRIPT
+# === COMPLETION SCRIPT END ===
 
 COMP_WORDS=( cli co )
 COMP_LINE="cli co"
diff --git a/spec/completely/zsh_spec.rb b/spec/completely/zsh_spec.rb
new file mode 100644
index 0000000..50c811b
--- /dev/null
+++ b/spec/completely/zsh_spec.rb
@@ -0,0 +1,35 @@
+require 'spec_helper'
+
+describe "zsh compatibility" do
+  let(:completions) { Completely::Completions.load 'spec/fixtures/basic.yaml' }
+  let(:words) { "completely generate " }
+  let(:tester_script) { completions.tester.tester_script words }
+  let(:shell) { 'zsh' }
+
+  before do
+    reset_tmp_dir
+    system "mkdir -p spec/tmp/somedir"
+    File.write "spec/tmp/test.sh", tester_script
+  end
+
+  subject do
+    Dir.chdir 'spec/tmp' do
+      `#{shell} test.sh`.strip
+    end
+  end
+
+  describe "completions script and test script" do
+    it "returns completions without erroring" do
+      expect(subject).to eq "somedir --help --force"
+    end
+
+    context "on bash" do
+      let(:shell) { 'bash' }
+      
+      it "returns the same output" do
+        expect(subject).to eq "somedir --help --force"
+      end
+    end
+  end
+
+end
\ No newline at end of file