diff --git a/.github/workflows/pytest.yml b/.github/workflows/pytest.yml
index ae3ed0a..6d40472 100644
--- a/.github/workflows/pytest.yml
+++ b/.github/workflows/pytest.yml
@@ -11,7 +11,7 @@ jobs:
       - name: Install python dependencies
         run: |
           python -m pip install --upgrade pip
-          python -m pip install --upgrade pytest
+          python -m pip install --upgrade pytest pytest-mock
       - name: Run pytest
         run: |
           python -m pytest -vv
diff --git a/README.rst b/README.rst
index f691f44..b9f33b6 100644
--- a/README.rst
+++ b/README.rst
@@ -66,20 +66,23 @@ command invocations:
 .. code-block:: text
 
    $ usbsdmux -h
-   usage: usbsdmux [-h] SG {get,dut,client,host,off}
+   usage: usbsdmux [-h] [--json] SG {get,dut,client,host,off,gpio,info} ...
 
    positional arguments:
      SG                    /dev/sg* to use
-     {get,dut,client,host,off}
-			   Action:
-			   get - return selected mode
-			   dut - set to dut mode
-			   client - set to dut mode (alias for dut)
-			   host - set to host mode
-			   off - set to off mode
-
-   optional arguments:
+     {get,dut,client,host,off,gpio,info}
+                           Supply one of the following commands to interact with the device
+       get                 Read the current state of the USB-SD-Mux
+       dut                 Switch to the DUT
+       client              Switch to the DUT
+       host                Switch to the host
+       off                 Disconnect from host and DUT
+       gpio                Manipulate a GPIO (open drain output only)
+       info                Show information about the SD card
+
+   options:
      -h, --help            show this help message and exit
+     --json                Format output as json. Useful for scripting.
 
 Using as root
 -------------
diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..b7390bb
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,43 @@
+import os
+
+import pytest
+
+import usbsdmux.__main__
+
+
+def test_usage(capsys, mocker):
+    "test that the usage output include the command name"
+    mocker.patch("sys.argv", ["usbsdmux"])
+    with pytest.raises(SystemExit):
+        usbsdmux.__main__.main()
+    captured = capsys.readouterr()
+    assert captured.out == ""
+    assert captured.err.startswith("usage: usbsdmux")
+
+
+def test_help_in_readme(capsys, mocker):
+    "test that the help output matches the readme"
+    mocker.patch("sys.argv", ["usbsdmux", "-h"])
+    with pytest.raises(SystemExit):
+        usbsdmux.__main__.main()
+    captured = capsys.readouterr()
+    assert captured.out.startswith("usage: usbsdmux")
+    assert captured.err == ""
+
+    readme_path = os.path.join(os.path.dirname(__file__), "../", "README.rst")
+    readme_lines = None
+    for line in open(readme_path).readlines():
+        line = line.rstrip()
+        if line == "   $ usbsdmux -h":
+            readme_lines = []
+        elif readme_lines is not None:
+            if line and not line.startswith("   "):
+                break
+            readme_lines.append(line)
+
+    assert readme_lines is not None
+    del readme_lines[-1]  # remove trailing empty line
+
+    output_lines = [f"   {line}".rstrip() for line in captured.out.splitlines()]
+
+    assert output_lines == readme_lines